tag:theconversation.com,2011:/ca/topics/disease-transmission-32984/articlesDisease transmission – The Conversation2023-11-21T12:07:28Ztag:theconversation.com,2011:article/2178382023-11-21T12:07:28Z2023-11-21T12:07:28ZNo compelling evidence that air purifiers prevent respiratory infections – new study<figure><img src="https://images.theconversation.com/files/560692/original/file-20231121-23-lg1s3r.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C8256%2C4634&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/air-purifier-comfortable-living-room-house-1914045592">Prathankarnpap/Shutterstock</a></span></figcaption></figure><p>The COVID pandemic led to many calls for improved <a href="https://time.com/6143799/covid-19-indoor-air-cleaning/">indoor air quality</a> with claims that doing so would reduce the risk of the <a href="https://www.scientificamerican.com/article/we-need-to-improve-indoor-air-quality-here-rsquo-s-how-and-why/">virus spreading</a>. But the real-world evidence to support these claims has been lacking and studies undertaken during the pandemic have not yet been reported. </p>
<p>So my colleagues and I reviewed the evidence before COVID and found that the balance of evidence was that air treatment does not, in fact, reduce illness from respiratory infections.</p>
<p>There are two main types of air treatment devices: <a href="https://link.springer.com/article/10.1007/s11157-015-9363-9">filters and air disinfectors</a>. Filters work by removing particles from the air that may contain infectious virus. Air disinfectors use ultraviolet radiation or ozone to inactivate viruses in the air.</p>
<p><a href="https://www.sciencedirect.com/science/article/pii/S0091743523003602">In our systematic review</a> we found 32 observational and experimental studies on the topic, conducted between 1970 and 2022. Overall, the evidence was that these technologies did not reduce either the frequency of illness or its severity. </p>
<p>When looking at the laboratory-confirmed influenza or norovirus infections, there was an apparent trend towards fewer infections. However, there was evidence of strong <a href="https://www.jclinepi.com/article/S0895-4356(99)00161-4/pdf">publication bias</a> – which is where significantly positive results are more likely to get published than negative results. </p>
<p>Publication bias makes the apparent impact of any intervention or treatment appear stronger than it is as those negative studies are simply not published.</p>
<p>Our review concluded that there is no strong evidence that air treatment technologies reduce the risks of respiratory transmitted illnesses.</p>
<p>None of the studies included in the review was directly about COVID, as none had been published during the study period. </p>
<p>However, a <a href="https://bmjopen.bmj.com/content/13/7/e072284">recent German study</a> (published in July), did investigate the effect of high-efficiency particulate air (Hepa) filters on COVID in kindergartens. The researchers compared illness rates in schools that had new filters installed with those that did not. </p>
<p>They found that there was no significant difference between the two. Indeed, infection rates were slightly higher in children in those schools that had the filters installed.</p>
<h2>What about ventilation?</h2>
<p>This study did not consider research on the effect of ventilation, such as keeping windows open, on the risk of illness. One possible issue with the studies of air treatment is that ventilation rates may have been reduced, thereby increasing risk. </p>
<p>There has been a recent systematic review of the effect of <a href="https://royalsocietypublishing.org/doi/full/10.1098/rsta.2023.0130">ventilation on COVID infection</a>. Although there was a bit more evidence in support of ventilation reducing infection, the studies were all of poor or very poor quality. As a result, the researchers concluded that the “level of confidence ascribed to this conclusion is low”. </p>
<p>So differences in ventilation are unlikely to explain the negative findings in the air treatment studies.</p>
<figure class="align-center ">
<img alt="A classroom with the window wide open." src="https://images.theconversation.com/files/560702/original/file-20231121-20-kzchb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/560702/original/file-20231121-20-kzchb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/560702/original/file-20231121-20-kzchb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/560702/original/file-20231121-20-kzchb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/560702/original/file-20231121-20-kzchb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/560702/original/file-20231121-20-kzchb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/560702/original/file-20231121-20-kzchb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Ventilation is unlikely to explain the poor performance of air filters.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/table-background-opened-window-schoolbag-view-1467628820">S Photo/Shutterstock</a></span>
</figcaption>
</figure>
<p>If air treatment does not reduce the risk of illness, why may that be the case? I would argue that there are several reasons air treatment technologies were never going to be the <a href="https://theconversation.com/covid-in-schools-how-ventilation-can-help-to-combat-spread-of-virus-165434">panacea</a> that some were <a href="https://www.gov.uk/government/news/more-support-to-keep-pupils-in-the-classroom">claiming</a>.</p>
<p>First, the risk of transmission of respiratory viruses depends on how close you are to an infected person. Early in the pandemic one group of scientists showed that the risk of infection dropped considerably the further <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31142-9/fulltext#seccestitle10">someone got from an infectious person</a>. </p>
<p>Someone who got within one metre of an infectious person was about five times at greater risk than someone who stayed more than one metre away. It is doubtful that air treatment would affect such close person-to-person transmission.</p>
<p>Second, even if air treatment was effective at preventing infection within a particular indoor space, people move regularly between spaces. Air treatment in your school or workplace will not protect you while on public transport or when gathering in other environments. </p>
<p>Finally, there is the issue of epidemic dynamics of infections that have a short duration of immunity. As I discussed over two years ago, infections like COVID that have a relatively short duration of immunity behave differently than would be predicted by <a href="https://theconversation.com/why-covid-cases-are-now-falling-in-the-uk-and-what-could-happen-next-165123">standard epidemic models</a> because people can be reinfected many times during their life as their immunity wanes. </p>
<p>Infections like COVID are better modelled by the SEIRS (susceptible, exposed, infected, recovered, susceptible) <a href="https://www.nature.com/articles/s41592-020-0856-2">model</a>. In this model, interventions like air filtration or wearing masks become less effective as most infections become reinfections. What then drives infection rates is the rate at which people lose their immunity. </p>
<p>So the balance of real-world evidence is that air treatment technologies do not reduce the risk of becoming ill from a respiratory infection like COVID. There is a little more evidence that increased ventilation may reduce that risk, but the evidence is far from compelling.</p><img src="https://counter.theconversation.com/content/217838/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paul Hunter consults for the World Health Organization. He receives funding from National Institute for Health Research, the World Health Organization and the European Regional Development Fund.</span></em></p>Air purifiers were meant to save us from COVID. A new systematic review wonders where the evidence for that is.Paul Hunter, Professor of Medicine, University of East AngliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2051672023-05-09T18:56:06Z2023-05-09T18:56:06ZDisinfectants and cleaning products harboring toxic chemicals are widely used despite lack of screening for potential health hazards<figure><img src="https://images.theconversation.com/files/525175/original/file-20230509-15-fcxskp.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2119%2C1414&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Quaternary ammonium compounds can linger on surfaces and in indoor air and dust long after the disinfectant has dried.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/spraying-disinfection-on-surface-royalty-free-image/1213050764">Guido Mieth/DigitalVision via Getty Images</a></span></figcaption></figure><p><em>The <a href="https://theconversation.com/us/topics/research-brief-83231">Research Brief</a> is a short take about interesting academic work.</em></p>
<h2>The big idea</h2>
<p><a href="http://dx.doi.org/10.1021/acs.est.2c08244">Concerns about unnecessary use</a> of a common class of antimicrobial chemicals used in disinfectants <a href="https://www.cdc.gov/hygiene/cleaning/cleaning-your-home.html">reinforces recommendations</a> to opt for <a href="https://ceh.org/household-cleaners/">soap and water</a> or <a href="https://www.turi.org/Our_Work/Cleaning_Laboratory/Safely_Clean_Disinfect/Safer_Disinfecting_Products">safer products</a>, my colleagues <a href="https://scholar.google.com/citations?user=1BQRKAsAAAAJ&hl=en">and I</a> determined in our recent critical review of the scientific literature.</p>
<p><a href="https://www.turi.org/TURI_Publications/TURI_Chemical_Fact_Sheets/Quaternary_Ammonium_Compounds_Fact_Sheet">Quaternary ammonium compounds, or QACs</a>, are increasingly marketed and used in homes, schools and workplaces with limited evidence for their appropriateness or safety. These chemicals can be found in common disinfectant solutions, wipes, hand sanitizers, sprays and even foggers.</p>
<p>Laboratory animal studies have found that some QACs can have <a href="http://dx.doi.org/10.1021/acs.est.2c08244">developmental and reproductive toxicity</a> with sustained exposure, may contribute to weight gain, and can impair energy production in cells.</p>
<p>Surprisingly, despite these concerns, studies on people <a href="http://dx.doi.org/10.1021/acs.est.2c08244">have been limited</a> to patients with allergic contact dermatitis and workplace-induced asthma among workers in hospitals and other facilities that require a sterile environment. We were even more surprised to find a lack of comprehensive screening for health hazards in the majority of this large class of common and widely used chemicals.</p>
<p>One of the top reasons to use antimicrobials only when needed is that overuse leads to the rise of <a href="https://theconversation.com/antibiotic-resistance-is-at-a-crisis-point-government-support-for-academia-and-big-pharma-to-find-new-drugs-could-help-defeat-superbugs-169443">antimicrobial resistance</a>, which contributes to millions of deaths per year worldwide. QACs and other antimicrobials create “superbugs” that not only can’t be killed by disinfectants but can also become resistant to lifesaving antibiotics.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/525199/original/file-20230509-21883-op1iqx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Gloved hands wiping doorknob" src="https://images.theconversation.com/files/525199/original/file-20230509-21883-op1iqx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/525199/original/file-20230509-21883-op1iqx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/525199/original/file-20230509-21883-op1iqx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/525199/original/file-20230509-21883-op1iqx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/525199/original/file-20230509-21883-op1iqx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/525199/original/file-20230509-21883-op1iqx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/525199/original/file-20230509-21883-op1iqx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Unnecessary disinfectant use can contribute to antimicrobial resistance and increase exposure to toxic chemicals.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/hands-with-glove-wiping-doorknob-royalty-free-image/1212740392">martinedoucet/E+ via Getty Images</a></span>
</figcaption>
</figure>
<h2>Why it matters</h2>
<p>When the COVID-19 pandemic began, recommendations circulated in the news and social media to disinfect almost everything, from doorknobs to desks <a href="https://www.npr.org/sections/health-shots/2020/04/12/832269202/no-you-dont-need-to-disinfect-your-groceries-but-here-s-to-shop-safely">to groceries</a>. Because COVID-19 is not primarily transmitted from surfaces, many of these disinfection practices <a href="https://www.cdc.gov/coronavirus/2019-ncov/more/science-and-research/surface-transmission.html">don’t substantially reduce transmission risk</a>.</p>
<p>Our team became concerned that frequent disinfectant use could lead to adverse health effects from QACs. Most people probably don’t know about existing health concerns regarding QACs, or aren’t aware that QACs can <a href="https://doi.org/10.1021%2Facs.estlett.0c00587">remain on surfaces and in indoor air and dust</a> long after the product has dried, exposing more people to these chemicals than just the initial user. Researchers have found that the <a href="https://doi.org/10.1021%2Facs.est.1c01654">average levels of these chemicals in people’s bodies</a> have risen since the pandemic began.</p>
<h2>What still isn’t known</h2>
<p>One of the most commonly used QACs is <a href="https://doi.org/10.1128%2FAEM.00377-19">benzalkonium chloride</a>. Others may be identified on ingredient labels with names that end in “<a href="https://www.turi.org/TURI_Publications/TURI_Chemical_Fact_Sheets/Quaternary_Ammonium_Compounds_Fact_Sheet/Regulations">ammonium chloride” or similar terms</a>.</p>
<p>While reading labels can help consumers identify QACs, some products <a href="https://cen.acs.org/articles/96/i12/US-chemical-industry-group-takes.html">may not require disclosure</a> of these chemicals in the ingredient list. For example, pesticide labels are required to list QACs whereas paint labels are not. QACs can be used in a wide variety of consumer products where they may or may not be listed when used, including personal care products, textiles, paints, medical instruments and more.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/525201/original/file-20230509-12843-axffgt.gif?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Table of common subclasses of QACs and associated products" src="https://images.theconversation.com/files/525201/original/file-20230509-12843-axffgt.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/525201/original/file-20230509-12843-axffgt.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=604&fit=crop&dpr=1 600w, https://images.theconversation.com/files/525201/original/file-20230509-12843-axffgt.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=604&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/525201/original/file-20230509-12843-axffgt.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=604&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/525201/original/file-20230509-12843-axffgt.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=759&fit=crop&dpr=1 754w, https://images.theconversation.com/files/525201/original/file-20230509-12843-axffgt.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=759&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/525201/original/file-20230509-12843-axffgt.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=759&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This table shows common subclasses of QACs and their associated products. QACs may not always be disclosed in the product label.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1021/acs.est.2c08244">Arnold et al./ACS</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<h2>What’s next</h2>
<p><a href="https://prhe.ucsf.edu/strengthening-chemical-regulatory-process">Reducing the harm of QACs</a> requires their disclosure in all products, comprehensively screening them for health hazards and closely monitoring their broader effects in people and on the environment.</p>
<p>In the meantime, my colleagues and I recommend that <a href="https://www.cdc.gov/hygiene/cleaning/cleaning-your-home.html">individuals</a>, <a href="https://www.cdc.gov/hygiene/cleaning/facility.html">schools and workplaces</a> take a close look at their cleaning practices to see where disinfectants can be replaced with <a href="https://ceh.org/household-cleaners/">safe cleaners</a> or <a href="https://www.turi.org/Our_Work/Cleaning_Laboratory/Safely_Clean_Disinfect/Safer_Disinfecting_Products">safer disinfectants</a>. </p>
<p>Cleaning with soap or detergent <a href="https://theconversation.com/is-bar-soap-as-gross-as-millennials-say-not-really-and-were-all-covered-with-microbes-anyway-141679">removes most types of harmful germs</a> like COVID-19 from surfaces. While disinfection can help kill any remaining microbes, it should be limited to situations <a href="https://www.cdc.gov/hygiene/cleaning/facility.html">where people have been actively ill</a>, such as vomit on a surface, and during certain disease outbreaks. </p>
<p>For disinfectants to work properly, they must be left on the surface long enough to kill the germs, and this required contact time may be noted on the product. When you <a href="https://www.epa.gov/coronavirus/cleaning-and-disinfecting-best-practices-during-covid-19-pandemic">use or handle disinfectants</a> you should wear protective gloves and eyeglasses or safety glasses, and you should open windows and doors to ventilate indoor spaces.</p><img src="https://counter.theconversation.com/content/205167/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Courtney Carignan receives funding from the National Institute of Environmental Health Sciences, National Institutes of Health, USEPA National Priorities Program, and USDA National Institute of Food and Agriculture. This document has not been formally reviewed by the funding agencies. The views expressed in this document are solely from the authors and do not necessarily reflect those from the funding agencies. </span></em></p>Quaternary ammonium compounds, also known as QACs or quats, are commonly used antimicrobials also found in many household products. Soap and water may be a safer bet when cleaning surfaces.Courtney Carignan, Assistant Professor of Food Science and Human Nutrition, Pharmacology and Toxicology, Michigan State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1965212023-01-18T06:10:52Z2023-01-18T06:10:52ZThe Black Death may not have been spread by rats after all<figure><img src="https://images.theconversation.com/files/500834/original/file-20221213-20582-djm1ng.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The black rat, or ship rat, was thought to have helped transmit the Black Death</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/black-rat-rattus-known-ship-roof-1607279755">Shutterstock / Carlos Aranguiz</a></span></figcaption></figure><p>The Black Death ravaged Europe between 1347 and 1353, killing millions. Plague outbreaks in Europe then continued until the 19th century. </p>
<p>One of the most commonly recited facts about plague in Europe was that it was spread by rats. In some parts of the world, the bacterium that causes plague, <em>Yersinia pestis</em>, maintains a long-term <a href="https://pubmed.ncbi.nlm.nih.gov/33264458/">presence in wild rodents and their fleas</a>. This is called an animal “reservoir”. </p>
<p>While plague begins in rodents, it sometimes spills over to humans. Europe may have once hosted animal reservoirs that sparked plague pandemics. But plague could have also been repeatedly reintroduced from Asia. Which of these scenarios was present remains a topic of scientific controversy.</p>
<p>Our recent research, <a href="https://www.pnas.org/doi/pdf/10.1073/pnas.2209816119">published in the Proceedings of the National Academy of Sciences (PNAS)</a>, has shown that environmental conditions in Europe would have prevented plague from surviving in persistent, long-term animal reservoirs. How, then, did plague persevere in Europe for so long? </p>
<p>Our study offers two possibilities. One, the plague was being reintroduced from Asian reservoirs. Second, there could have been short- or medium-term temporary reservoirs in Europe. In addition, the two scenarios might have been mutually supportive.</p>
<p>However, the rapid spread of the Black Death and subsequent outbreaks of the next few centuries also suggest slow-moving rats may not have played the critical role in transmitting the disease that is often portrayed.</p>
<h2>European climate</h2>
<p>To work out whether plague could survive in long-term animal reservoirs in Europe, we examined factors such as soil characteristics, climatic conditions, terrain types and rodent varieties. These all seem to affect whether plague can hold on in reservoirs.</p>
<p>For example, high concentrations of some elements in soil, including copper, iron, magnesium, as well as a high soil pH (whether it is acidic or alkaline), cooler temperatures, higher altitudes and lower rainfall appear to favour the development of persistent reservoirs, though it is not entirely clear why, at this stage.</p>
<p>Based on our comparative analysis, centuries-long wild rodent plague reservoirs were even less likely to have existed from the Black Death of 1348 to the early 19th century than today, when comprehensive research <a href="https://cdn.who.int/media/docs/default-source/documents/emergencies/health-topics---plague/who_hse_epr_2008_3w.pdf">rules out any such reservoirs within Europe.</a> </p>
<p>This contrasts sharply with regions across China and the western US, where <a href="https://www.pnas.org/doi/pdf/10.1073/pnas.2209816119">all the above conditions</a> for persistent <em>Yersinia pestis</em> reservoirs in wild rodents are found.</p>
<p>In central Asia, long-term and persistent rodent reservoirs may have existed for millennia. <a href="https://academic.oup.com/past/article-abstract/252/1/3/6120066">As ancient DNA and textual evidence hints</a>, once plague crossed into Europe from central Asia, it appears to have seeded a short- or medium-term reservoir or reservoirs in European wild rodents. The most likely place for this to have been was in central Europe.</p>
<p>However, as local soil and climatic conditions did not favour long-term and persistent reservoirs, the disease had to be re-imported, <a href="https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1001134">at least in some instances</a>. Importantly, the two scenarios are not mutually exclusive. </p>
<h2>Radical difference</h2>
<p>To go deeper into the role of rats in spreading plague in Europe, we can compare different outbreaks of the disease.</p>
<p>The first plague pandemic began in the early sixth century and lasted until the later eighth century. The second pandemic (which included the Black Death) began in the 1330s and lasted five centuries. A third pandemic began in 1894 and remains with us today in places such as Madagascar and <a href="https://www.nbcnews.com/health/health-news/california-confirms-first-human-case-bubonic-plague-5-years-what-n1237306">California</a>.</p>
<p>These pandemics overwhelmingly involved the bubonic form of plague, where the bacteria infect the human lymphatic system (which is part of the body’s immune defences). In pneumonic plague, the bacteria infect the lungs.</p>
<p>The plagues of the second pandemic differed radically in their character and transmission from more recent outbreaks. First, there were strikingly different levels of mortality, with some second pandemic outbreaks reaching 50%, while those of the third pandemic rarely exceeded 1%. <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2018.2429">In Europe, figures for the third pandemic were even lower.</a></p>
<figure class="align-center ">
<img alt="Steppe marmot or Bobak marmot" src="https://images.theconversation.com/files/500836/original/file-20221213-23347-moof54.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/500836/original/file-20221213-23347-moof54.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/500836/original/file-20221213-23347-moof54.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/500836/original/file-20221213-23347-moof54.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/500836/original/file-20221213-23347-moof54.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/500836/original/file-20221213-23347-moof54.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/500836/original/file-20221213-23347-moof54.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Outside Europe, rodents such as this steppe marmot act as long-term reservoirs for the bacterium that causes plague.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/bobak-marmot-marmota-known-steppe-species-1935805306">Roman Rys / Shutterstock</a></span>
</figcaption>
</figure>
<p>Second, there were different rates and patterns of transmission between these two plague epochs. There were massive differences in the frequency and speed of transporting goods, animals, and people between the late middle ages and today (or the late 19th century). Yet the Black Death and many of its subsequent waves spread with astonishing speed. Over land, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2630035/">it raced almost as fast each day</a> as the modern outbreaks do over a year. </p>
<p>As described by contemporary chroniclers, physicians, and others – and as reconstructed quantitatively from archival documents – the plagues of the second pandemic <a href="https://academic.oup.com/ije/article/31/6/1280/939560">spread faster and more widely than any other disease during the middle ages.</a> Indeed they were faster than in any period until the <a href="https://academic.oup.com/book/7179">cholera outbreaks from 1830 or the great influenza of 1918-20.</a></p>
<p>Regardless of how the various European waves of the second pandemic began, both wild and non-wild rodents – rats, first and foremost – move much slower than the pace of transmission around the continent.</p>
<p>Third, the seasonality of plague also shows wide discrepancies. Plagues of the third pandemic (except for the rare ones, principally of pneumonic plague) have closely followed the fertility cycles of rat fleas. These rise with relatively humid conditions (although lower rainfall is important for plague reservoirs to first become established) <a href="https://parasitesandvectors.biomedcentral.com/articles/10.1186/1756-3305-4-191">and within a temperature band between 10°C and 25°C.</a></p>
<p>By contrast, plagues of the second pandemic could cross winter months in bubonic form, as seen across the Baltic regions from 1709-13. But in Mediterranean climes, plague from 1348 through the 15th century was a summer contagion that peaked in June or July – <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2630035/">during the hottest and driest months.</a> </p>
<p>This deviates strikingly from plague seasons <a href="https://royalsociety.org/blog/2019/04/third-plague-pandemic-europe/">in these regions in the 20th century.</a> Because of the low relative humidity and high temperatures, these months were then the least likely times for plague to break out among rats or humans.</p>
<p>These differences raise a crucial question about whether the bubonic form of the plague depended on slow-moving rodents for its transmission when instead it could <a href="http://www.pnas.org/content/early/2018/01/09/1715640115">spread much more efficiently directly, from person to person</a>. Scientists have speculated that this could have occurred because of ectoparasites (fleas and possibly lice), or through people’s respiratory systems and through touch.</p>
<p>Questions such as the precise roles played by humans and rats in past plague pandemics need further work to resolve. But as shown by this study, and others, major steps forward can be made when scientists and historians work together.</p><img src="https://counter.theconversation.com/content/196521/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Recent research suggests rats may not have played the critical role in keeping plague going in Europe.Samuel Cohn, Professor of History, University of GlasgowPhilip Slavin, Associate Professor of History, University of StirlingLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1957172022-12-08T10:18:22Z2022-12-08T10:18:22ZToilets spew invisible aerosol plumes with every flush – here’s the proof, captured by high-powered lasers<figure><img src="https://images.theconversation.com/files/499634/original/file-20221207-11275-dvj7o.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C3863%2C4784&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Aerosol plumes from commercial toilets can rise 5 feet above the bowl.</span> <span class="attribution"><span class="source">John Crimaldi/Scientific Reports</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>Every time you flush a toilet, it releases plumes of tiny water droplets into the air around you. These droplets, called <a href="https://doi.org/10.1063/5.0040310">aerosol plumes</a>, can spread pathogens from human waste and expose people in public restrooms to contagious diseases. </p>
<p>Scientific understanding of the spread of aerosol plumes – and public awareness of their existence – has been hampered by the fact that they are normally invisible. My colleagues <a href="https://scholar.google.com/citations?user=cGGI4QcAAAAJ&hl=en">Aaron True</a>, <a href="https://scholar.google.com/citations?user=uAS7KNUAAAAJ&hl=en">Karl Linden</a>, <a href="https://scholar.google.com/citations?user=BpJEifoAAAAJ&hl=en">Mark Hernandez</a>, Lars Larson and Anna Pauls and I were able to use <a href="https://www.nature.com/articles/s41598-022-24686-5">high-power lasers to illuminate these plumes</a>, enabling us to image and measure the location and motion of spreading aerosol plumes from flushing commercial toilets in vivid detail.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/oC_f0UAGwMU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This video compares the visibility of an aerosol plume after a flush without and with lasers in a lab.</span></figcaption>
</figure>
<h2>Going up instead of down</h2>
<p>Toilets are designed to efficiently empty the contents inside the bowl through a downward motion into the drain pipe. In the flush cycle, water comes into forceful contact with the contents inside the bowl and creates a fine spray of particles suspended in air. </p>
<p>We found that a typical commercial toilet generates a strong upward jet of air with velocities exceeding 6.6 feet per second (2 meters per second), rapidly carrying these particles up to 5 feet (1.5 meters) above the bowl within eight seconds of the start of the flush.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/499624/original/file-20221207-11419-91m3jz.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram of jet-siphonic toilet" src="https://images.theconversation.com/files/499624/original/file-20221207-11419-91m3jz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/499624/original/file-20221207-11419-91m3jz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/499624/original/file-20221207-11419-91m3jz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/499624/original/file-20221207-11419-91m3jz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/499624/original/file-20221207-11419-91m3jz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/499624/original/file-20221207-11419-91m3jz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/499624/original/file-20221207-11419-91m3jz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Water streams forcefully into the toilet bowl during a flush cycle.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Diagram_of_a_jet-siphonic_WC_bowl.svg">SouthHamsian/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<p>To visualize these plumes, we set up a typical lidless commercial toilet with a <a href="https://doi.org/10.1080%2F02786826.2013.814911">flushometer-style valve</a> found throughout North America in our lab. Flushometer valves use pressure instead of gravity to direct water into the bowl. We used special optics to create a thin vertical sheet of laser light that illuminated the region from the top of the bowl to the ceiling. After flushing the toilet with a remote electrical trigger, the aerosol particles scatter enough laser light to become visible, allowing us to use cameras to image the plume of particles. </p>
<p>Even though we expected to see these particles, we were still surprised by the strength of the jet ejecting the particles from the bowl.</p>
<p>A <a href="https://doi.org/10.1063/5.0013318">related study</a> used a computational model of an idealized toilet to predict the formation of aerosol plumes, with an upward transport of particles at speeds above the bowl approaching 3.3 feet per second (1 meter per second), which is about half of what we observed with a real toilet.</p>
<h2>Why lasers?</h2>
<p>Scientists have known <a href="https://doi.org/10.1016/j.gsf.2021.101282">for decades</a> that flushing toilets can release aerosol particles into the air. However, <a href="https://doi.org/10.1038/s41598-021-02938-0">experimental studies</a> have largely relied on devices that sampled the air at fixed locations to determine the number and size of particles toilets produce.</p>
<p>While these earlier approaches can confirm the presence of aerosols, they provide little information about the physics of the plumes: what they look like, how they spread and how fast they move. This information is critical to develop strategies to mitigate the formation of aerosol plumes and reduce their capacity to transmit disease.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/ReSTeXwcfYw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This video shows Aaron True monitoring the live image data of a flushing toilet plume on a computer screen.</span></figcaption>
</figure>
<p>As an <a href="https://scholar.google.com/citations?user=wn_f7y0AAAAJ&hl=en">engineering professor</a> whose research focuses on interactions between fluid physics and ecological or biological processes, <a href="https://www.colorado.edu/lab/ecological-fluids/">my laboratory</a> specializes in using lasers to determine how various things are <a href="https://doi.org/10.1017/jfm.2015.113">transported by complex fluid flows</a>. In many cases, these things are invisible until we illuminate them with lasers.</p>
<p>An advantage of using laser light to measure fluid flows is that, unlike a physical probe, light does not alter or disrupt the very thing you are trying to measure. Furthermore, using lasers to make invisible things visible helps people, as <a href="https://doi.org/10.2147%2FEB.S64016">visual creatures</a>, better understand complexities in the fluid environment they live in.</p>
<h2>Aerosols and disease</h2>
<p>Aerosol particles containing pathogens are important <a href="https://doi.org/10.1097/JOM.0000000000000448">human disease vectors</a>. Smaller particles that remain suspended in air for a period of time can expose people to respiratory diseases like <a href="https://doi.org/10.1126/science.abd9149">influenza and COVID-19</a> through inhalation. Larger particles that settle quickly on surfaces can spread intestinal diseases like <a href="https://doi.org/10.1038/s41598-021-02938-0">norovirus</a> through contact with the hands and mouth.</p>
<p>Toilet bowl water contaminated by feces can have pathogen concentrations that <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5890808/">persist after dozens</a> of flushes. But it is still <a href="https://doi.org/10.2166/wh.2021.182">an open question</a> as to whether toilet aerosol plumes present a transmission risk.</p>
<p>While we were able visually and quantitatively to describe how aerosol plumes move and disperse, our work does not directly address how toilet plumes transmit disease, and this remains an ongoing aspect of research. </p>
<h2>Limiting toilet plume spread</h2>
<p>Our experimental methodology provides a foundation for future work to test a range of strategies to minimize the risk of exposure to diseases from flushing toilets. This could include assessing changes to aerosol plumes emanating from new toilet bowl designs or flush valves that change the duration or intensity of the flush cycle.</p>
<p>Meanwhile, there are ways to reduce human exposure to toilet plumes. An obvious strategy is to <a href="https://doi.org/10.1016/j.scitotenv.2020.142575">close the lid</a> prior to flushing. However, this does not completely eliminate aerosol plumes, and many toilets in public, commercial and health care settings do not have lids. Ventilation or <a href="https://doi.org/10.1111/ina.12752">UV disinfection</a> systems could also mitigate exposure to aerosol plumes in the bathroom.</p><img src="https://counter.theconversation.com/content/195717/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Crimaldi receives funding from the National Science Foundation, National Institutes of Health, and the US Army DEVCOM Chemical Biological Center. </span></em></p>Toilets eject aerosol droplets that may carry disease-causing pathogens. Learning about how these particles move could help reduce exposure in public restrooms.John Crimaldi, Professor of Civil, Environmental and Architectural Engineering, University of Colorado BoulderLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1914102022-10-07T12:20:10Z2022-10-07T12:20:10ZInvesting in indoor air quality improvements in schools will reduce COVID transmission and help students learn<figure><img src="https://images.theconversation.com/files/488350/original/file-20221005-26-dd8eky.jpg?ixlib=rb-1.1.0&rect=19%2C4%2C3091%2C2116&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An air scrubber in a classroom at the E.N. White School in Holyoke, Mass.</span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/VirusOutbreakSchoolFunding/6403884a83214a09a776339d3a6055c0/photo">AP Photo/Charles Krupa</a></span></figcaption></figure><p>As fall temperatures cool across the U.S., many schools will struggle to ventilate classrooms while also keeping students and teachers comfortable and healthy. Children and teachers spend <a href="https://nces.ed.gov/surveys/sass/tables/sass0708_035_s1s.asp">over six hours a day</a> in classrooms during the school year, often in buildings that are <a href="https://www.epa.gov/iaq-schools/take-action-improve-indoor-air-quality-schools">decades old</a> and have <a href="https://edlabor.house.gov/imo/media/doc/School%20Districts%20Frequently%20Identified%20Multiple%20Building%20Systems%20Needing%20Updates%20or%20Replacement1.pdf">inadequate heating, ventilation and air conditioning</a>, or HVAC, systems.</p>
<p>Fall 2022 marks the start of the fourth school year affected by the COVID-19 pandemic, which has spotlighted the importance of <a href="https://www.cdc.gov/mmwr/volumes/71/wr/mm7123e2.htm">indoor air quality in schools</a>. Ideally, all school buildings would have adequate <a href="https://www.rand.org/pubs/research_reports/RRA1393-1.html">ventilation</a>, filtered air in each classroom and windows that open. Sadly, this is not the case – and indoor air quality in many schools <a href="https://time.com/6206343/schools-ventilation-covid-19-air-quality/">is poor as a result</a>. This is especially problematic in the wake of the U.S. Centers for Disease Control and Prevention’s <a href="https://www.cdc.gov/coronavirus/2019-ncov/community/schools-childcare/k-12-childcare-guidance.html">August 2022 COVID-19 guidance for schools</a>, which scales back other measures for limiting transmission, such as masking, testing and quarantining. </p>
<p>Beyond minimizing COVID-19 transmission, indoor air quality also matters for student academic performance. This is especially important given the <a href="https://www.npr.org/2022/06/22/1105970186/pandemic-learning-loss-findings">learning losses</a> that many children experienced in the first two years of the pandemic. <a href="http://dx.doi.org/10.1257/pol.20180612">Hot, stuffy classrooms</a> make it harder for students to learn. So do <a href="https://www.northjersey.com/story/news/essex/montclair/2021/12/14/montclair-covid-schools-cold-hvac/6445845001/">cold classrooms</a>.</p>
<p>Our research focuses on <a href="https://scholar.google.com/citations?user=LB_MQNAAAAAJ&hl=en&oi=ao">indoor environments</a> <a href="https://scholar.google.ca/citations?user=iR82G3IAAAAJ&hl=en">and health</a> – an area that has received increased attention during the pandemic, since most COVID-19 transmission occurs through <a href="https://www.whitehouse.gov/ostp/news-updates/2022/03/23/lets-clear-the-air-on-covid/">shared air indoors</a>. There is <a href="https://www.epa.gov/iaq-schools/evidence-scientific-literature-about-improved-academic-performance#IAQIAP_AdequateAir">ample evidence</a> that smart investments in school buildings can reduce transmission of infectious disease, while also improving learning and increasing well-being for students, teachers and administrators.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1545536518961463297"}"></div></p>
<p>Many school districts have limited resources and <a href="https://theconversation.com/america-gets-a-d-for-school-infrastructure-but-federal-covid-relief-could-pay-for-many-repairs-156831">buildings in poor condition</a>. Where should they start? Here are some priorities we see for immediate action and longer-term investments that can truly transform the school experience.</p>
<h2>Filters and fresh air</h2>
<p>Since the spring of 2020, schools have invested millions of dollars in interventions to reduce COVID-19 transmission, including high-efficiency, free-standing <a href="https://www.cps.edu/press-releases/chicago-public-schools-invests-%2482.5-million-to-provide-hepa-air-purifiers-for-every-classroom/">commercial filter units</a> and <a href="https://www.cdc.gov/mmwr/volumes/71/wr/mm7123e2.htm?s_cid=mm7123e2_w">ventilation upgrades</a>. These actions are a drop in the bucket, given <a href="https://www.gao.gov/assets/gao-20-494.pdf">the structural improvements needed in many schools</a>, especially in less wealthy school districts, but they are an important start. And their benefits extend beyond COVID-19, so they should not be discarded.</p>
<p>For example, high-efficiency filters – including commercial units, <a href="https://engineering.ucdavis.edu/news/science-action-how-build-corsi-rosenthal-box">DIY boxes</a> or <a href="https://www.epa.gov/coronavirus/what-kind-filter-should-i-use-my-home-hvac-system-help-protect-my-family-covid-19">filters with ratings of MERV-13</a> for HVAC systems – capture flu and common cold viruses as well as SARS-CoV-2 virus particles. They also clean the air of pollen particles, mold spores and <a href="https://doi.org/10.1101/2022.01.12.22269175">pollution from car exhaust and industrial operations</a>. And in areas where wildfires are common, filters <a href="https://www.cdc.gov/air/wildfire-smoke/socialmedia/wildfire-air-filtration-508.pdf">reduce the concentration of smoke particles</a> inside buildings. </p>
<p>Schools with mechanical ventilation have been able to increase the amount of filtered fresh air that these systems pull indoors. This dilutes all indoor pollutants. For kids and school staff, particularly those with asthma, allergies and sensitivities, this can mean <a href="https://doi.org/10.1111/ina.12042">fewer missed days of school, less medication, and fewer asthma attacks</a> and subsequent trips to the hospital.</p>
<p>Improved ventilation can actually increase learning and attention. A 2010 study showed that kids performed better on standardized tests <a href="https://doi.org/10.1111/j.1600-0668.2010.00686.x">when ventilation rates were higher</a>. Poor ventilation may also affect teachers: A 2016 study found that office workers’ cognitive performance improved when they were <a href="https://doi.org/10.1289/ehp.1510037">exposed to lower carbon dioxide levels</a>, which is a marker of better ventilation. And a 2018 analysis showed that students’ performance on school tests <a href="http://dx.doi.org/10.3386/w24639">declined on hot days, especially in schools without air conditioning</a>. If you’ve ever felt that it was hard to concentrate in a hot, stuffy room, the science backs you up.</p>
<p>For now, we recommend that schools that have put improvements in place should maintain increased ventilation rates with maximum fresh air, continue to use high-efficiency filters in their HVAC systems and keep free-standing filters running in classrooms. Schools that have not invested in these steps should do so, with states providing funding to lower-resourced districts as needed. The costs of these steps are modest compared with the <a href="https://doi.org/10.1111/ina.12042">benefits they provide for health and learning</a>. </p>
<p>Families and staff who want to improve conditions in their schools should focus on providing every classroom with improved ventilation and filtration, including <a href="https://aghealth.ucdavis.edu/news/corsi-rosenthal-box-diy-box-fan-air-filter-covid-19-and-wildfire-smoke">building DIY boxes, if necessary</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/hIuH-2naozI?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A Corsi-Rosenthal Box is a homemade air cleaning system that can reduce indoor exposure to airborne particles containing the virus that causes COVID-19. It can also reduce the levels of other particles in the air, such as dust or wildfire smoke.</span></figcaption>
</figure>
<h2>Funding for healthier buildings</h2>
<p>These near-term solutions can help, but the best way to ensure that schools provide healthy conditions for learning is by investing in healthier buildings. </p>
<p>Funds for this purpose <a href="https://www.ed.gov/improving-ventilation-schools-colleges-and-universities-prevent-covid-19">are available now</a>. All U.S. states have received millions of dollars from the <a href="https://www.whitehouse.gov/american-rescue-plan/">American Rescue Plan</a>, enacted in 2021 to address the impact of COVID-19, including <a href="https://oese.ed.gov/offices/education-stabilization-fund/elementary-secondary-school-emergency-relief-fund/">Elementary and Secondary Schools Emergency Relief</a>, or ESSER, funds. The Department of Education has disbursed US$122 billion to help schools prevent the spread of COVID-19 and operate safely. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/EsCEvAKjeSo?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">With fewer COVID-19 precautions such as masking and testing in place for the fall of 2022, Charlotte-Mecklenburg schools are continuing to invest in air filtration and cleaning ducts to improve air circulation in school buildings.</span></figcaption>
</figure>
<p>School districts have used this money to address a <a href="https://www.future-ed.org/local-covid-relief-spending/">variety of needs</a>, including staffing, academic support and mental health, but much of it is still available. And only a handful of states have <a href="https://www.contractingbusiness.com/iaq-ventilation/article/21235009/connecticuts-lamont-supports-hvac-upgrades-in-schools">invested in HVAC</a>. According to a review by the independent Brookings Institution, <a href="https://www.brookings.edu/blog/brown-center-chalkboard/2022/03/31/a-year-ago-school-districts-got-a-windfall-of-pandemic-aid-hows-that-going/">less than 5%</a> of the money from the most recent round of ESSER funds had been spent through the first quarter of 2022. </p>
<p>Another <a href="https://www.americanprogress.org/article/how-states-and-cities-can-benefit-from-climate-investments-in-the-inflation-reduction-act/">$3 billion</a> was authorized in the recently enacted <a href="https://www.whitehouse.gov/briefing-room/statements-releases/2022/08/19/fact-sheet-the-inflation-reduction-act-supports-workers-and-families/">Inflation Reduction Act</a> for environmental and climate justice block grants. These can be used to upgrade buildings and ventilation systems to reduce indoor air pollution.</p>
<p>School districts may be tempted to put indoor air interventions on the back burner, given widespread perceptions that <a href="https://www.cbsnews.com/news/president-joe-biden-60-minutes-interview-transcript-2022-09-18/">the pandemic is over</a> and the many other challenges they face. But in our view, other educational interventions will be less effective if kids are frequently absent due to illness or unable to concentrate in the classroom. </p>
<p>We believe it is important for families and staff to understand the benefits that healthy indoor learning environments offer to everyone who spends time in school buildings, and to hold states and school districts accountable for investing now in HVAC improvements for <a href="https://www.usgbc.org/articles/federal-funding-sustainable-schools">healthier school buildings</a>.</p><img src="https://counter.theconversation.com/content/191410/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A lot of federal money is now available for making school buildings healthier. Two environmental health experts explain how school districts can best use it.Patricia Fabian, Associate Professor of Environmental Health, Boston UniversityJonathan Levy, Professor and Chair, Department of Environmental Health, Boston UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1828802022-05-17T18:31:53Z2022-05-17T18:31:53ZOn the trail of the origins of Covid-19<figure><img src="https://images.theconversation.com/files/462448/original/file-20220511-14-wmpaxu.jpg?ixlib=rb-1.1.0&rect=0%2C23%2C4000%2C2215&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cave inhabited by bats.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/fr/image-photo/huge-group-bats-waits-patiently-exit-1440955400">Sanatana/Shutterstock</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>As the Covid-19 virus (coronavirus SARS-CoV-2) continues to spread and claim victims worldwide, its <a href="https://www.nature.com/articles/d41586-022-00732-0">origins</a> remain unknown. Each scientific community puts forward its own <a href="https://www.theguardian.com/world/2021/dec/31/why-hunt-for-covid-origins-still-wrapped-in-politics-impasse-china-west">theory</a>, with some suggesting the virus may have leaked out of a <a href="https://theconversation.com/covid-19-why-the-lab-leak-theory-must-be-formally-investigated-161297">laboratory</a>.</p>
<p>Another theory, based on recent studies of the <a href="https://www.science.org/content/article/do-three-new-studies-add-proof-covid-19-s-origin-wuhan-animal-market">Wuhan wet market</a> in China, along with others carried out in <a href="https://www.nature.com/articles/s41467-021-26809-4">Cambodia</a>, <a href="https://www.nature.com/articles/s41586-022-04532-4">Laos, Japan, China, and Thailand</a>, posits that an ancestral virus in rhinolophus bats went on from infecting wild and/or domestic animals to humans. Indeed, in these different studies, several viruses with genetic sequences very similar to SARS-CoV-2 were isolated in these bats.</p>
<h2>A missing link</h2>
<p>Though it has been shown some bat species have hosted these coronaviruses naturally, the wild or domestic animal (or animals) that acted as a bridge between them and humans – the missing link – remains unidentified. Pangolins were first suspected, but now appear to have been collateral victims rather than one of these much-talked-about missing links. A coronavirus genome sequence detected in pangolins was indeed related to that of SARS-CoV-2, but the rest of the genome was <a href="https://link.springer.com/article/10.1007/s10311-020-01151-1">too distant from it genetically</a> to back the hypothesis.</p>
<p>Moreover, the pangolins hosts in which the viruses that were genetically close to SARS-CoV-2 were found had mostly been confiscated at live-animal markets, at the end of the supply chain. As a result, they had been in lengthy contact with other animal species. It is very likely they were infected along this supply chain rather than in their natural environment. <a href="https://theconversation.com/origin-of-the-covid-19-virus-the-trail-of-mink-farming-155989">Mink farms</a> were also suspected of being an intermediate host in China.</p>
<p>Lastly, pangolins and rhinolophus bats do not share the same habitat, making it highly unlikely there was any contact between the two species in which the virus jumped from one to the other. On the other hand, civets and raccoon dogs could be an intermediate source of <a href="https://pubmed.ncbi.nlm.nih.gov/16140765/">SARS-CoV-1</a>). Rodents or primates could also carry pathogens with zoonotic potential, such as hantaviruses – which can cause haemorrhagic fever with renal syndrome – or filoviruses, <a href="https://www.pnas.org/doi/10.1073/pnas.2002324118">which include the Ebola virus</a>. The latter is passed on to humans through wild animals, in particular bats, antelopes, and primates such as chimpanzees and gorillas, then spreads among humans, mainly by direct contact with blood, secretions and other bodily fluids from infected people. The average case fatality rate is around 50%.</p>
<p>In 2013, initial cases of disease from the Ebola virus were detected in <a href="https://pubmed.ncbi.nlm.nih.gov/34424896">West Africa</a>. The rise of these cases led to over 10,000 deaths, mainly in Guinea, Liberia, and Sierra Leone.</p>
<h2>The risky habit of bushmeat-eating</h2>
<p>Activities such as hunting, animal-handling or eating meat from wild animals therefore create the conditions for viruses to spread from animals to humans – a potentially devastating phenomenon called “spillover”.</p>
<p>The <a href="https://www.cirad.fr/en/cirad-news/news/2020/science/covid-19-zoocov-a-new-project-to-prevent-coronavirus-transmission-from-wildlife-to-humans">ZooCov</a> project has sought to define and quantify this risk in Cambodia. For almost two years – and right from the start of the pandemic – it has adopted a <a href="https://www.oie.int/en/what-we-do/global-initiatives/one-health/">“One Health”</a> approach to explore whether – and how – pathogens such as coronaviruses can be passed on to humans from wild animals that are hunted and eaten.</p>
<p>Indeed, in South-East Asia, wild animals are regularly traded, and bushmeat is customarily eaten. This eating habit is often opportunistic. In some communities, it complements a low-protein diet. It can also be frequent and targeted. In Cambodia, 77% of 107 families interviewed in the ZooCov project said they had eaten bushmeat in the <a href="https://www.cirad.fr/en/cirad-news/news/2022/coronavirus-surveillance-a-concrete-example-of-the-one-health-approach-in-action-in-cambodia">past month</a>.</p>
<p>Use for medicinal purposes is also widespread. In Vietnam, an <a href="https://pubmed.ncbi.nlm.nih.gov/35356028/">analysis of records</a> of the Vietnamese authorities confiscating pangolins and related by-products between 2016 and 2020 reported 1,342 live pangolins (6,330 kg), 759 dead pangolins or pangolin carcasses (3,305 kg), and 43,902 kg of pangolin scales.</p>
<p>Yet this consumption also has a cultural and social dimension that is still not properly understood. Among the well-off – and often in big cities – people sometimes eat bushmeat out of a desire for social status, and a belief that eating it endows them with the physical or physiological <a href="https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30063-3/fulltext">attributes</a> of the animal. They also sometimes eat bushmeat out of rejection of industrially produced meat, considered unhealthy. Animals are widely reared to meet this demand and the demand for <a href="https://www.who.int/publications/i/item/WHO-2019-nCoV-fur-farming-risk-assessment-2021.1">fur production</a>.</p>
<p>In the Stung Treng and Mondolkiri provinces of Cambodia, where protected forest areas remain, researchers surveyed more than 900 people living on the edge of these forests to determine the structure of the illegal bushmeat trade. Statistical analyses are underway to identify the people most at risk of contact with wildlife thus with such pathogens. We already know those exposed are mostly young middle-class men, and that some communities are more exposed than others. Sociological studies have also helped better grasp today’s context: the legal framework, the profiles of players in the trade, their motives and deterrents in trade and consumption of wild animals, and how the context has changed with each different health crisis (bird flu, Ebola, SARS-CoV-1, etc.).</p>
<h2>Which populations are most at risk?</h2>
<p>These successive crises seem to have scarcely affected the habits of these communities. Beyond regularly eating bushmeat, one fourth of the families surveyed said they still hunted or ensnared wild animals, and 11% claimed to sell bushmeat or wild animals. Furthermore, in the same areas of study, over 2,000 samples taken from wild animals trafficked or eaten for subsistence – bats, rodents, turtles, monkeys, birds, wild pigs, etc. – were analysed. Some of these samples tested positive for coronaviruses and scientists at the Institut Pasteur du Cambodge (IPC) are currently sequencing their genome in a bid to learn more about their origin, evolution, and zoonotic potential. Finally, researchers collected blood samples from over 900 people from the same region to find out whether they had been in contact with a coronavirus or coronaviruses. These analyses are still underway, but what we do know is that these people had not been exposed to SARS-CoV-2 when the survey was conducted.</p>
<p>If the Covid crisis has taught us anything, it is the importance of detecting such emergences early in order to nip the pathogens in the bud. While many questions remain about the way cases emerge, there are just as many questions about the monitoring systems that should be set up to track them. The results of the ZooCov project will be used to develop a system for detecting spillover of zoonotic viruses early, particularly by strengthening the system for monitoring wildlife health that is already in operation in Cambodia, which was set up by the <a href="https://cambodia.wcs.org/Initiatives/Wildlife-Health.aspx">Wildlife Conservation Society</a> (WCS). Other large-scale projects in research and development will help us understand, detect, and prevent these phenomena of emerging cases.</p>
<hr>
<p><em>The authors would like to thank Cambodia’s Ministry of Health, its Ministry of Agriculture, Forestry and Fisheries, and its Ministry of Environment, as well as all the project’s partners: Institut Pasteur du Cambodge (IPC), the Wildlife Conservation Society (WCS), Flora and Fauna International (FFI), Institut de Recherche pour le Développement (IRD), Hong Kong University (HKU), the GREASE network, International Development Enterprise (iDE), the World Wildlife Fund (WWF), Elephant Livelihood Initiative Environment (ELIE), BirdLife International, Jahoo, and World Hope International.</em></p>
<p><em>Translated from the French by Thomas Young for <a href="http://www.fastforword.fr/en">Fast ForWord</a>.</em></p><img src="https://counter.theconversation.com/content/182880/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Véronique Chevalier a reçu des financements de l'Agence Nationale de la Recherche (ANR), la Région Occitanie et la Fondation Pasteur.</span></em></p><p class="fine-print"><em><span>François Roger et Julia Guillebaud ne travaillent pas, ne conseillent pas, ne possèdent pas de parts, ne reçoivent pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'ont déclaré aucune autre affiliation que leur poste universitaire.</span></em></p>Scientists exploring the possibility of an animal origin for Covid-19 are still investigating the missing link between bats and human beings.Véronique Chevalier, Veterinarian epidemiologist, CiradFrançois Roger, Directeur régional Asie du Sud-Est, vétérinaire et épidémiologiste, CiradJulia Guillebaud, Ingénieure de recherche , Institut PasteurLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1708562021-12-01T13:35:43Z2021-12-01T13:35:43ZCharting changes in a pathogen’s genome yields clues about its past and hints about its future<figure><img src="https://images.theconversation.com/files/434799/original/file-20211130-14-gx51zb.jpg?ixlib=rb-1.1.0&rect=50%2C100%2C6176%2C4134&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A virus's genes hold a record of where it's traveled, and when.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/global-pandemic-infographic-royalty-free-image/1270842570">imaginima/E+ via Getty Images</a></span></figcaption></figure><p>More than <a href="https://ourworldindata.org/covid-cases?country=%7EOWID_WRL">250 million people worldwide</a> have tested positive for SARS-CoV-2, usually after a diagnostic nose swab. Those swabs aren’t trash once they’ve delivered their positive result, though. For <a href="https://scholar.google.com/citations?user=L7pQoysAAAAJ&hl=en&oi=ao">scientists</a> <a href="https://scholar.google.com/citations?user=aDRW1JMAAAAJ&hl=en&oi=ao">like</a> <a href="https://scholar.google.com/citations?user=9hWmfYoAAAAJ&hl=en&oi=ao">us</a> they carry additional valuable information about the coronavirus. Leftover material from swabs can help us uncover hidden aspects of the COVID-19 pandemic.</p>
<p>Using what are called phylodynamic methods that can track a pathogen’s travels via changes in its genes, researchers are able to pinpoint factors like <a href="https://doi.org/10.1073/pnas.2012008118">where and when outbreaks start</a>, the <a href="https://doi.org/10.1038/s43856-021-00031-1">number of undetected infections</a> and <a href="https://doi.org/10.1038/s41467-020-19346-z">common routes of transmission</a>. Phylodynamics can also aid in understanding and tracking the spread of new pathogen variants, such as the recently detected <a href="https://twitter.com/trvrb/status/1464353224417325066">omicron variant of SARS-CoV-2</a>.</p>
<h2>What’s in a swab?</h2>
<p>Pathogens, just like people, each have a genome. This is RNA or DNA that contains an organism’s genetic code – its instructions for life and the information necessary for reproduction. </p>
<p>It’s now relatively <a href="https://www.nature.com/articles/d42859-020-00103-7">fast</a> and <a href="https://www.genome.gov/about-genomics/fact-sheets/DNA-Sequencing-Costs-Data">cheap</a> to sequence a pathogen’s genome. In Switzerland, <a href="https://bsse.ethz.ch/cevo/research/sars-cov-2/swiss-sars-cov-2-sequencing-consortium.html">a consortium of government and academic scientists</a> that we’re a part of as already extracted viral genome sequences from <a href="https://cov-spectrum.ethz.ch/explore/Switzerland/AllSamples/AllTimes">almost 80,000 SARS-CoV-2 positive swab tests</a>.</p>
<p>By lining up genetic sequences obtained from different patients, scientists can see which positions in the sequence differ. These differences represent mutations, small errors incorporated into the genome when the pathogen copies itself. We can use these mutational differences as clues to reconstruct chains of transmission and learn about epidemic dynamics along the way. </p>
<h2>Phylodynamics: Piecing together genetic clues</h2>
<p><a href="https://doi.org/10.1126/science.1090727">Phylodynamic methods</a> provide a way to describe how mutational differences relate to epidemic dynamics. These approaches allow researchers to get from the raw data about where mutations have occurred in the viral or bacterial genome to understanding all the implications. It might sound complicated, but it’s actually pretty easy to give an intuitive idea of how it works. </p>
<p>Mutations in the pathogen genome get passed from person to person in a transmission chain. Many pathogens acquire lots of <a href="https://doi.org/10.1016/S0169-5347(03)00216-7">mutations over the course of an epidemic</a>. Scientists can summarize these mutational similarities and differences using what’s essentially a family tree for the pathogen. Biologists call it <a href="https://docs.nextstrain.org/en/latest/learn/interpret/how-to-read-a-tree.html">a phylogenetic tree</a>. Each branching point represents a transmission event, when the pathogen moved from one person to another.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/434467/original/file-20211129-19-1niweey.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="diagram of sample to sequence to tree" src="https://images.theconversation.com/files/434467/original/file-20211129-19-1niweey.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/434467/original/file-20211129-19-1niweey.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=225&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434467/original/file-20211129-19-1niweey.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=225&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434467/original/file-20211129-19-1niweey.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=225&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434467/original/file-20211129-19-1niweey.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=283&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434467/original/file-20211129-19-1niweey.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=283&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434467/original/file-20211129-19-1niweey.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=283&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A phylogenetic tree is an approximation of the past transmission chain, based on variations in the pathogen’s genetic sequence.</span>
<span class="attribution"><span class="source">Guinat, Windels, Nadeau</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The branch lengths are proportional to the number of differences between sequenced samples. Short branches mean little time between branching points – fast transmission from person to person. Studying the length of branches on this tree can tell us about pathogen spread in the past – maybe even before we knew an epidemic was on the horizon.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/434470/original/file-20211129-15-rzms02.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="diagram of hypothetical virus outbreak's phylogenetic tree" src="https://images.theconversation.com/files/434470/original/file-20211129-15-rzms02.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/434470/original/file-20211129-15-rzms02.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=254&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434470/original/file-20211129-15-rzms02.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=254&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434470/original/file-20211129-15-rzms02.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=254&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434470/original/file-20211129-15-rzms02.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=319&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434470/original/file-20211129-15-rzms02.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=319&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434470/original/file-20211129-15-rzms02.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=319&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Pathogen genome sequences can be used to construct phylogenetic trees and estimate hidden epidemic dynamics. Shorter branches stand for quicker transmission.</span>
<span class="attribution"><span class="source">Guinat, Windels, Nadeau</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Mathematical models of disease dynamics</h2>
<p>Models in general are simplifications of reality. They try to describe core real-life processes with mathematical equations. In phylodynamics, these equations describe the relationship between epidemic processes and the phylogenetic tree. </p>
<p>Take, for example, tuberculosis. It’s the <a href="https://www.who.int/publications/i/item/9789240037021">deadliest bacterial infection in the world</a>, and it is getting even more threatening because of the widespread evolution of antibiotic resistance. If you catch an antibiotic-resistant version of the tuberculosis bacterium, <a href="https://doi.org/10.1186/s40249-016-0214-x">treatment can take years</a>.</p>
<p>To predict the future burden of resistant tuberculosis, we want to estimate how fast it spreads.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/434837/original/file-20211130-14-kaj3am.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="diagram of epidemiological processes in transmission of TB" src="https://images.theconversation.com/files/434837/original/file-20211130-14-kaj3am.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/434837/original/file-20211130-14-kaj3am.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=432&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434837/original/file-20211130-14-kaj3am.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=432&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434837/original/file-20211130-14-kaj3am.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=432&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434837/original/file-20211130-14-kaj3am.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=543&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434837/original/file-20211130-14-kaj3am.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=543&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434837/original/file-20211130-14-kaj3am.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=543&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Epidemiologists work to track infections as the pathogen moves through a population.</span>
<span class="attribution"><span class="source">Guinat, Windels, Nadeau</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>To do this, we need a model that captures two important processes. First, there’s the course of infection, and second, there’s the development of antibiotic resistance. In real life, infected people can infect others, get treatment and, in the end, either be cured or, in the worst case, die from the infection. On top of this, the pathogen can develop resistance.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/434480/original/file-20211129-27-e5whvt.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="diagram of information fed into mathematical model" src="https://images.theconversation.com/files/434480/original/file-20211129-27-e5whvt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/434480/original/file-20211129-27-e5whvt.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=282&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434480/original/file-20211129-27-e5whvt.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=282&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434480/original/file-20211129-27-e5whvt.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=282&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434480/original/file-20211129-27-e5whvt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=354&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434480/original/file-20211129-27-e5whvt.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=354&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434480/original/file-20211129-27-e5whvt.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=354&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Phylodynamic models capture real-life epidemiological processes into mathematical equations and parameters.</span>
<span class="attribution"><span class="source">Guinat, Windels, Nadeau</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We can translate these epidemiological processes into a mathematical model with two groups of patients – one group infected with normal tuberculosis and one with antibiotic-resistant tuberculosis. The important processes – transmission, recovery and death – can happen at different rates for each group. Finally, patients whose infection develops antibiotic resistance move from the first group to the second.</p>
<p>This model does ignore some aspects of tuberculosis outbreaks, such as asymptomatic infections or relapses after treatment. Even so, when applied to a set of tuberculosis genomes, this model helps us <a href="https://doi.org/10.1016/j.epidem.2021.100471">estimate how fast resistant tuberculosis spreads</a>. </p>
<h2>Capturing hidden aspects of epidemics</h2>
<p>Uniquely, phylodynamic approaches can help researchers answer questions in situations where diagnosed cases do not give the full picture. For example, what about the number of undetected cases or the source of a new epidemic? </p>
<p>A good example of this type of genome-based investigation is our recent work on <a href="https://ec.europa.eu/food/animals/animal-diseases/diseases-and-control-measures/avian-influenza_en#hpai-epidemic-20162017">highly pathogenic avian influenza (HPAI)</a> H5N8 in Europe. This epidemic spread to poultry farms and wild birds across <a href="https://doi.org/10.1111/tbed.12861">30 European countries</a> in 2016. In the end, <a href="https://www.bbc.com/news/world-europe-54825971">tens of millions of birds</a> were culled, devastating the poultry industry.</p>
<p>But were poultry farms or wild birds the real driver of spread? Obviously we cannot ask the birds themselves. Instead, phylodynamic modeling based on H5N8 genomes sampled from poultry farms and wild birds helped us get an answer. It turns out that in some countries the pathogen mainly spread from farm to farm, while in others it spread from wild birds to farms. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/433527/original/file-20211123-21-lof9wy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="ducks outside" src="https://images.theconversation.com/files/433527/original/file-20211123-21-lof9wy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/433527/original/file-20211123-21-lof9wy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=381&fit=crop&dpr=1 600w, https://images.theconversation.com/files/433527/original/file-20211123-21-lof9wy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=381&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/433527/original/file-20211123-21-lof9wy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=381&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/433527/original/file-20211123-21-lof9wy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=479&fit=crop&dpr=1 754w, https://images.theconversation.com/files/433527/original/file-20211123-21-lof9wy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=479&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/433527/original/file-20211123-21-lof9wy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=479&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Phylodynamic models can estimate the number of avian influenza virus transmissions between wild birds and poultry.</span>
<span class="attribution"><span class="source">C. LeGall</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>In the case of HPAI H5N8, <a href="https://doi.org/10.1101/2021.10.22.465255">we helped animal health authorities focus control efforts</a>. In some countries this meant limiting transmission between poultry farms while in others limiting contact between domestic and wild birds.</p>
<p>More recently, phylodynamic analyses helped evaluate the impact of control strategies for SARS-CoV-2, including the <a href="https://doi.org/10.1073/pnas.2012008118">first border closures</a> and <a href="https://doi.org/10.1038/s41467-020-20235-8">strict early lockdowns</a>. A big advantage of phylodynamic modeling is that it can account for undetected cases. The models can even describe early stages of the outbreak in the absence of samples from that time period. </p>
<p>Phylodynamic models are under intensive development, continuously expanding the field to new applications and larger datasets. However, there are still challenges in extending genome sequencing efforts to undersampled species and regions and upholding <a href="https://doi.org/10.1038/d41586-021-00331-5">rapid public data sharing</a>. Ultimately, these data and models will help everyone gain new insights on epidemics and how to control them.</p>
<p>[<em>The Conversation’s science, health and technology editors pick their favorite stories.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-favorite">Weekly on Wednesdays</a>.]</p><img src="https://counter.theconversation.com/content/170856/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Claire Guinat receives funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 842621.</span></em></p><p class="fine-print"><em><span>Sarah Nadeau receives funding from the Swiss National Science Foundation and ETH Zurich. </span></em></p><p class="fine-print"><em><span>Etthel Windels does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>After a nose swab tests positive for a virus or bacteria, scientists can use the sample’s genetic sequence to figure out where and when the pathogen emerged and how fast it’s changing.Claire Guinat, Postdoctoral Fellow in Computational Evolution, Swiss Federal Institute of Technology ZurichEtthel Windels, Postdoctoral Fellow in Computational Evolution, Swiss Federal Institute of Technology ZurichSarah Nadeau, PhD Student in Computational Evolution, Swiss Federal Institute of Technology ZurichLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1611662021-05-25T12:13:39Z2021-05-25T12:13:39ZCan people vaccinated against COVID-19 still spread the coronavirus?<figure><img src="https://images.theconversation.com/files/402429/original/file-20210524-19-1pkj1h1.jpg?ixlib=rb-1.1.0&rect=0%2C255%2C4788%2C3447&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Vaccinated people are well protected from getting sick, but could they inadvertently transmit the coronavirus?</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/people-walk-in-hudson-river-park-on-may-23-2021-in-new-york-news-photo/1319716519">Noam Galai/Getty Images Entertainment via Getty Images</a></span></figcaption></figure><p><strong>Takeaways:</strong></p>
<ul>
<li>Vaccines can be great at preventing you from getting sick, while at the same time not necessarily stopping you from getting infected or spreading the germ.</li>
<li>Preliminary evidence seems to suggest the COVID-19 vaccines make it less likely someone who’s vaccinated will transmit the coronavirus, but the proof is not yet ironclad.</li>
<li>Unvaccinated people should still be diligent about mask-wearing, physical distancing and other precautions against the coronavirus.</li>
</ul>
<hr>
<p>When the U.S. Centers for Disease Control and Prevention <a href="https://www.whitehouse.gov/briefing-room/press-briefings/2021/05/13/press-briefing-by-white-house-covid-19-response-team-and-public-health-officials-36/">changed its guidelines about mask-wearing</a> on May 13, 2021, plenty of Americans were left a little confused. Now anyone who is fully vaccinated can participate in indoor and outdoor activities, large or small, without wearing a mask or physical distancing.</p>
<p>Anthony Fauci, chief medical adviser to President Biden, said the new guideline is “<a href="https://www.cbsnews.com/news/transcript-dr-anthony-fauci-face-the-nation-05-16-2021/">based on the evolution of the science</a>” and “serves as an incentive” for the <a href="https://covid.cdc.gov/covid-data-tracker/#vaccinations">almost two-thirds of Americans</a> who are not yet fully vaccinated to go ahead and get the shot.</p>
<p>But some people <a href="https://www.cdc.gov/vaccines/covid-19/info-by-product/clinical-considerations.html">cannot be vaccinated</a> because of underlying conditions. Others with weakened immune systems, from cancer or medical treatments, <a href="https://www.medrxiv.org/content/10.1101/2021.03.17.21253131v1">may not be fully protected</a> <a href="https://www.medrxiv.org/content/10.1101/2021.04.06.21254949v1">by their vaccinations</a>. <a href="https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-pfizer-biontech-covid-19-vaccine-emergency-use">Children aged 12 to 15 became eligible</a> for the Pfizer-BioNTech vaccine only on May 10, 2021. And <a href="https://www.cdc.gov/vaccines/covid-19/info-by-product/clinical-considerations.html">no COVID-19 vaccines are yet authorized</a> for the nearly <a href="https://www.childstats.gov/americaschildren/tables/pop1.asp">50 million children</a> in the U.S. younger than 12.</p>
<p>As restrictions are lifted and people start to leave their masks at home, some people worry: Can you catch COVID-19 from someone who’s vaccinated?</p>
<h2>Vaccines don’t always prevent infection</h2>
<p>Researchers had hoped to <a href="https://www.fda.gov/regulatory-information/search-fda-guidance-documents/emergency-use-authorization-vaccines-prevent-covid-19">design safe COVID-19 vaccines</a> that would <a href="https://www.fda.gov/media/139638/download">prevent at least half</a> of the people vaccinated from getting COVID-19 symptoms.</p>
<p>Fortunately, the vaccines have <a href="https://doi.org/10.1056/NEJMc2102153">vastly</a> <a href="https://doi.org/10.1016/S0140-6736(21)00947-8">outperformed</a> expectations. For example, <a href="https://doi.org/10.1016/S0140-6736(21)00947-8">in 6.5 million residents of Israel</a>, aged 16 years and older, the Pfizer–BioNTech mRNA COVID-19 vaccine was found to be 95.3% effective after both shots. Within two months, among the 4.7 million fully vaccinated, the detectable infections fell by 30-fold. Similarly in <a href="https://doi.org/10.1056/NEJMc2101927">California</a> and <a href="https://doi.org/10.1056/NEJMc2102153">Texas</a>, only 0.05% of fully vaccinated health care workers tested positive for COVID-19.</p>
<p>Vaccine developers often hope that, in addition to preventing illness, their vaccines will achieve “<a href="https://doi.org/10.1038/srep32973">sterilizing immunity</a>,” where the vaccination blocks the germ from even being able to get into the body at all. This sterilizing immunity means someone who’s vaccinated will neither catch the virus nor transmit it further. For a vaccine to be effective, though, it doesn’t need to prevent the germ from infecting an immunized person. </p>
<p>The <a href="https://www.cdc.gov/vaccines/vpd/polio/index.html">Salk inactivated polio vaccine</a>, for instance, <a href="https://doi.org/10.1016/B978-0-323-04404-2.10092-2">does not completely stop</a> polio virus from growing in the human gut. But it <a href="https://medicine.yale.edu/news/yale-medicine-magazine/breaking-the-back-of-polio/">is extremely effective</a> at preventing the crippling disease because it triggers antibodies that block the virus from infecting the brain and spinal cord. Good <a href="https://doi.org/10.1016/B978-0-323-04404-2.10092-2">vaccines provide effective and durable training</a> for the body’s immune system, so when it actually encounters the disease-causing pathogen, it’s ready to mount an optimum response. </p>
<p>When it comes to COVID-19, immunologists are still figuring out what they call the “<a href="https://doi.org/10.1016/S0140-6736(21)00782-0">correlates of protection</a>,” factors that predict just how protected someone is against the coronavirus. Researchers believe that <a href="https://www.nature.com/articles/s41591-021-01377-8">an optimum amount</a> of “<a href="https://www.sciencedirect.com/topics/neuroscience/neutralizing-antibody">neutralizing antibodies</a>,” the type that not only bind the virus but also prevent it from infecting, are sufficient to fend off <a href="https://doi.org/10.1016/S0140-6736(21)00675-9">repeat infections</a>. Scientists are also still assessing the <a href="https://doi.org/10.1056/NEJMc2032195">durability of immunity</a> that the COVID-19 vaccines are providing and <a href="https://doi.org/10.1101/2021.05.06.21256403">where in the body</a> it’s working. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/402430/original/file-20210524-19-aq22jo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="stickers given out to people who get vaccinated" src="https://images.theconversation.com/files/402430/original/file-20210524-19-aq22jo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/402430/original/file-20210524-19-aq22jo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=384&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402430/original/file-20210524-19-aq22jo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=384&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402430/original/file-20210524-19-aq22jo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=384&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402430/original/file-20210524-19-aq22jo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=483&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402430/original/file-20210524-19-aq22jo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=483&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402430/original/file-20210524-19-aq22jo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=483&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Vaccination can mean far fewer infections, but it’s not clear it will stop transmission by those who are vaccinated.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/stickers-are-stacked-up-for-people-receiving-vaccinations-news-photo/1319347246">Ethan Miller/Getty Images News</a></span>
</figcaption>
</figure>
<h2>Can a vaccinated person spread coronavirus?</h2>
<p>Immunologists expect vaccines that protect against viral illnesses to also reduce transmission of the virus after vaccination. But it’s actually tricky to figure out for sure if vaccinated people are not spreading the germ.</p>
<p>COVID-19 poses a particular challenge because people with asymptomatic and pre-symptomatic infections can spread the disease – and insufficient contact tracing and testing mean those without symptoms <a href="https://doi.org/10.1126/science.abf9569">are rarely detected</a>. Some scientists estimate that the number of asymptomatic COVID-19 infections in the overall population <a href="https://doi.org/10.1038/s41467-020-18272-4">could be 3 to 20 times higher</a> than the number of confirmed cases. Research suggests that undocumented cases of COVID-19 in people who either were asymptomatic or experienced very mild disease could be responsible for <a href="https://doi.org/10.1126/science.abb3221">up to 86% of all infections</a>, though other studies <a href="https://doi.org/10.3138/jammi-2020-0030">contradict the high estimates</a>.</p>
<p>In <a href="https://www.cdc.gov/mmwr/volumes/70/wr/mm7013e3.htm?s_cid=mm7013e3_w">one study</a>, the CDC tested volunteer health care personnel and other front-line workers at eight U.S. locations for SARS-CoV-2 infections weekly for three months, regardless of symptoms or vaccination status. The researchers found that fully immunized participants were 25 times less likely to test positive for COVID-19 than were those who were unvaccinated. Findings like this imply that if vaccinated people are so well protected from getting infected at all, they are <a href="https://www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/fully-vaccinated-people.html">also unlikely to spread</a> the virus. But without contact tracing to track transmission in a larger population, it’s impossible to know if the assumption is true.</p>
<p>What we know for sure is that if someone does get sick with COVID-19 after vaccination, in what is called a “breakthrough infection,” <a href="https://doi.org/10.1056/NEJMoa2105000">symptoms will be milder</a>. Studies have found that people who tested positive for COVID-19 after getting <a href="https://www.nature.com/articles/s41591-021-01316-7">just their first vaccine dose</a> had <a href="https://www.medrxiv.org/content/10.1101/2021.02.06.21251283v1">lower levels of virus in their bodies</a> than unvaccinated people who tested positive. The researchers believe the decreased viral load hints that vaccinated people who do contract the virus <a href="https://doi.org/10.1016/S1473-3099(20)30985-3">will be less infectious</a> because they will have much less virus that could be spread to others.</p>
<p>A preprint study which has not yet been peer-reviewed suggests that the Moderna mRNA COVID-19 vaccine can produce coronavirus-fighting <a href="https://doi.org/10.1101/2021.05.06.21256403">antibodies in the oral and nasal fluid</a>. Since <a href="https://doi.org/10.1371/journal.ppat.1009037">that’s where SARS-CoV-2 makes its entry</a>, antibodies in the mouth and nose should block the virus from getting into the body, effectively providing “sterilizing immunity.” This would also mean vaccinated people probably wouldn’t spread the virus through respiratory droplets.</p>
<p>These bits of evidence are promising. But without more studies, scientists <a href="https://doi.org/10.1038/d41586-021-00450-z">cannot yet conclude</a> that COVID-19 vaccines really do protect against all transmission. <a href="https://preventcovidu.org/">Studies attempting</a> to directly answer this question through contact tracing are just beginning: Researchers will track COVID-19 infections among vaccinated and unvaccinated volunteers and their close contacts.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/402431/original/file-20210524-13-5jiayj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="coronavirus precaution signs in multiple languages hang on a fence" src="https://images.theconversation.com/files/402431/original/file-20210524-13-5jiayj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/402431/original/file-20210524-13-5jiayj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402431/original/file-20210524-13-5jiayj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402431/original/file-20210524-13-5jiayj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402431/original/file-20210524-13-5jiayj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402431/original/file-20210524-13-5jiayj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402431/original/file-20210524-13-5jiayj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">CDC guidance still calls for those who are not yet vaccinated to mask up and maintain physical distance.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/wear-a-face-covering-sign-in-three-languages-flushing-news-photo/1310967691">Education Images/Universal Images Group via Getty Images</a></span>
</figcaption>
</figure>
<h2>Protection and prevention go hand in hand</h2>
<p>Vaccines help slow down the spread of an infectious disease by breaking the chain of infection. Those who are infected eventually have fewer and fewer unprotected people to pass the virus on to. This is how a vaccine increases <a href="https://www.who.int/news-room/q-a-detail/herd-immunity-lockdowns-and-covid-19">herd immunity</a> – susceptible and not-yet-immunized people are surrounded by a “herd” of people who have become immune, thanks to vaccination or previous infection. But studies suggest that, for a combination of biological and <a href="https://www.kff.org/coronavirus-covid-19/poll-finding/kff-covid-19-vaccine-monitor-april-2021/">social reasons</a>, <a href="https://doi.org/10.1016/S1473-3099(21)00143-2">vaccination alone is unlikely</a> to achieve herd immunity against COVID-19 and fully contain the coronavirus.</p>
<p>In fact, vaccination <a href="https://doi.org/10.1146/annurev.publhealth.20.1.211">alone can take a long time</a> to eradicate any disease. Even diseases that are nearly “eliminated” – such as chickenpox, measles and pertussis – <a href="https://doi.org/10.1001/jama.2016.1353">can resurface</a> with waning immunity and declining vaccine rates. </p>
<p>The recent outbreak of infections among the <a href="https://www.npr.org/2021/05/14/996873507/what-to-make-of-the-yankees-outbreak-scientists-say-dont-panic-we-expected-this">vaccinated New York Yankees</a> shows that vaccinated people not only can still get infected, they might also transmit the coronavirus to close contacts. Highly tested groups, such as professional sports teams, spotlight the fact that mild, asymptomatic infections among the vaccinated in the general population might actually be more frequent than reported. A similar <a href="https://www.straitstimes.com/singapore/speed-at-how-changi-airport-covid-19-cluster-grew-is-worrying-says-expert">outbreak in airport workers in Singapore</a> shows that, even among the fully vaccinated, new and more infectious variants can spread fast. </p>
<p>The CDC’s relaxed guidelines on masking are meant to reassure vaccinated people that they are safe from serious illness. And they are. But the picture is less clear-cut for the unvaccinated who interact with them. Until near herd immunity against COVID-19 is achieved, and clear evidence accumulates that vaccinated people do not spread the virus, I and <a href="https://www.nytimes.com/2021/05/13/upshot/epidemiologists-coronavirus-masks.html">many epidemiologists</a> believe it is better to avoid situations where there are chances to get infected. Vaccination coupled with <a href="https://www.pnas.org/content/118/4/e2014564118">continued masking</a> and social distancing is still an effective way to stay safer.</p>
<p>[<em><a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-corona-important">The Conversation’s most important coronavirus headlines, weekly in a science newsletter</a></em>]</p><img src="https://counter.theconversation.com/content/161166/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sanjay Mishra receives funding from the National Cancer Institute through his institution. </span></em></p>The COVID-19 vaccines are a smash success. But that doesn’t mean they keep every vaccinated person completely free of the coronavirus.Sanjay Mishra, Project Coordinator & Staff Scientist, Vanderbilt University Medical Center, Vanderbilt UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1556072021-03-01T18:56:25Z2021-03-01T18:56:25ZHow Arctic sea ducks develop herd immunity from avian cholera<figure><img src="https://images.theconversation.com/files/386755/original/file-20210226-13-121bebj.jpg?ixlib=rb-1.1.0&rect=33%2C0%2C7436%2C4972&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Avian cholera is a highly contagious disease that has produced rapid population loss in Northern common eiders.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>Herd immunity, when a threshold proportion of a population becomes immune to a disease-causing organism, reducing or stopping further transmission, is very much in the news. Avian cholera much less so. But there is an intersection between these two subjects that appears to have played out over eight summers between 2005 and 2012 at the largest colony of Arctic-nesting sea ducks, specifically Northern common eiders, in the Canadian Arctic.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-is-herd-immunity-52377">Explainer: what is herd immunity?</a>
</strong>
</em>
</p>
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<p>To wildlife disease ecologists, an ideal place to test ideas about herd immunity is Mitivik Island, Nunavut. The sea duck colony on this well-demarcated 24-hectare island was exposed to avian cholera in the recent past. This population, long-monitored by Inuit and researchers, was likely entirely naïve, or previously unexposed, to this disease before 2005.</p>
<p>Avian cholera is a disease of birds, caused by an entirely different bacterial species than that responsible for human cholera. Notably, both diseases can lead to outbreaks among their hosts as they are highly transmissible between individuals and highly infectious. When tens to hundreds of dead or dying waterfowl are found locally and are not showing overt signs of emaciation, it could very well signal an avian cholera epidemic.</p>
<p>Avian cholera has been responsible for rapid and mass die-offs of birds around the world, but it is particularly problematic for waterfowl in North America where epidemics are relatively common.</p>
<p>Our research on avian cholera suggested herd immunity resulted in the flip side of an outbreak, called an <a href="https://doi.org/10.1038/s41598-020-79888-6">epidemic fadeout</a>. </p>
<p>In wildlife, as in humans, immunity can be naturally or artificially generated, principally due to heightened antibody and T-cell responses to the infectious organism itself or due to vaccination against the agent or a (biologically engineered) part of it. </p>
<h2>Natural immunity</h2>
<p>Sea duck immunity was all natural. Cholera antibody levels were determined by laboratory screening of frozen and archived blood samples, as a sort of cold case investigation.</p>
<p>We found the average antibody level in the sea ducks correlated inversely with infection rate. For example, antibody levels were high among sea ducks in years when death rates among nesting hens were low. This variable provided an estimate of the mathematical term R0, which is shorthand for the average number of new infections generated by a single infected individual. R0 was widely variable among years, but was not correlated with the proportion of birds carrying the bacterium estimated from genetic tests, nor was it associated with annual population size of sea ducks on the island. Only average antibody level was an important predictor of R0.</p>
<p>Why should we care about sea ducks and avian cholera? These Northern common eiders are free-ranging but colony-nesting birds that can provide important tests of factors affecting localized epidemics in wildlife. Our scientific study was meant to determine if the proportion of birds carrying healthy reserves of antibodies to avian cholera negatively affected susceptible birds returning to nest — and whether protective herd immunity of remaining naïve birds resulted. Herd immunity appeared to have been reached, but it was not without its demographic insults.</p>
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<figcaption><span class="caption">An overview of the threat posed by avian cholera to the common eider.</span></figcaption>
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<h2>Losses on the way to herd immunity</h2>
<p>The local breeding population lost approximately 3,000 birds — or 36 per cent of its nesting birds — through mortality caused by avian cholera in the summer of 2006. The numbers of breeding hens on Mitivik Island were reduced by upwards of half over the entire course of the cholera epidemic from an all-time high of over 8,000 breeding hens. </p>
<p>This outbreak threatened the viability of this colony, and similar fears are being raised about eiders in Iceland as the disease has <a href="https://doi.org/10.1371/journal.pone.0029659">reached its shores in the past couple of years</a>.</p>
<p>Because herd immunity is not perfect (populations exchange naïve and infected individuals), the disease still smoulders among Arctic eiders colonies. Local outbreaks, likely from movement to and from sites with smouldering infections, repeated throughout the many smaller Arctic nesting colonies, which led to studies on environmental correlates of disease occurrence, most notably spring migratory routes from wintering sites in Atlantic Canada to the Arctic breeding sites.</p>
<p>Arctic eiders are culturally important. Common eiders, known collectively by Inuit as Mitiq along with King eiders, are part of a subsistence economy. There is a local trade built around collecting feather down for winter clothing and harvesting eggs and the birds for consumption. </p>
<p>Understanding threats to the viability of populations of these sea ducks may seem crucial to protecting this subsistence economy. But avian cholera outbreaks may <a href="https://wcvmtoday.usask.ca/articles/2021/01/study-credits-herd-immunity-for-stopping-deadly-disease-among-sea-ducks.php">not be manageable in the Canadian Arctic where populations are widespread but dispersed and difficult to access with management options</a>. The reality might be just to wait it out.</p><img src="https://counter.theconversation.com/content/155607/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Forbes receives funding from Natural Sciences and Engineering Research Council of Canada (NSERC) and Environment and Climate Change Canada (ECCC) through their Grants and Contributions envelope.</span></em></p>We can learn about the spread of diseases through populations by studying naturally occurring instances of herd immunity. Avian cholera in the Canadian Arctic provides a useful case study.Mark Forbes, Professor, Biology, Carleton UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1550322021-02-10T08:01:49Z2021-02-10T08:01:49ZWhat are nebulisers? And how could they help spread COVID-19?<figure><img src="https://images.theconversation.com/files/383442/original/file-20210210-19-un89cd.jpg?ixlib=rb-1.1.0&rect=0%2C2%2C998%2C558&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/oxygen-mask-nebulizer-medical-equipment-pneumonia-1771466849">from www.shutterstock.com</a></span></figcaption></figure><p>A nebuliser — a medical device that turns a liquid into a fine mist, typically to deliver inhaled medication — may have spread the coronavirus in Melbourne’s hotel quarantine.</p>
<p>Victoria’s Chief Health Officer Brett Sutton <a href="https://www.abc.net.au/news/2021-02-10/victoria-holiday-inn-covid-quarantine-hotel-to-close/13139224">said earlier today</a> this was the “working hypothesis” to explain why three people became infected at the airport’s Holiday Inn hotel.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1359298604641488897"}"></div></p>
<p>How could this have happened? And what are the implications for people who use nebulisers outside hotel quarantine, such as those with asthma?</p>
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Read more:
<a href="https://theconversation.com/another-hotel-worker-tests-positive-in-melbourne-its-time-to-move-hotel-quarantine-out-of-cities-154820">Another hotel worker tests positive in Melbourne. It's time to move hotel quarantine out of cities</a>
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</em>
</p>
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<h2>What is a nebuliser?</h2>
<p>A nebuliser creates a fine mist from a liquid, usually using compressed air or oxygen, or via ultrasonic vibration. A nebuliser is different to a vaporiser, which uses heat to produce a mist. </p>
<p>Nebulisers are often used to deliver life-saving drugs. Patients inhale them via a mask they put over their nose and mouth. Sometimes the mist alone is sufficient to provide a treatment. For example, nebulised saline <a href="https://www.cff.org/Life-With-CF/Treatments-and-Therapies/Medications/Mucus-Thinners">is used to treat</a> the lung condition cystic fibrosis. Sometimes people with asthma or chronic obstructive pulmonary disease are also treated with drugs via a nebuliser.</p>
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<strong>
Read more:
<a href="https://theconversation.com/im-an-asthmatic-what-should-i-do-during-the-coronavirus-pandemic-135309">I'm an asthmatic: what should I do during the coronavirus pandemic?</a>
</strong>
</em>
</p>
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<h2>How could a nebuliser potentially spread COVID-19?</h2>
<p>When we breathe in and out, the very small airways and the air sacs in our lungs open and close. This generates particles. These particles, along with water vapour, are what are commonly referred to as exhaled aerosols. Think back to breathing out on a cold day; the mist was aerosols from your lungs.</p>
<p>When we have a viral respiratory infection, the virus can be contained in the particles we exhale, and this is how aerosol transmission occurs. It is now widely accepted that SARS-CoV-2, the virus that causes COVID-19, <a href="https://theconversation.com/how-the-coronavirus-spreads-through-the-air-5-essential-reads-146735">can be spread via aerosols</a>, as well as via larger droplets when we cough and sneeze.</p>
<p>Any activity that increases the amount of aerosols, for example singing or exercising, can increase the amount of aerosolised virus, thereby increasing the risk of transmission.</p>
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Read more:
<a href="https://theconversation.com/this-video-shows-just-how-easily-covid-19-could-spread-when-people-sing-together-144789">This video shows just how easily COVID-19 could spread when people sing together</a>
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<p>When people use a nebuliser, two things happen. The first is they often take in big breaths and exhale more forcefully than normal. This alone increases the amount of particles generated. The second is they breathe in a fine mist, not all of which is absorbed in the lung. This too is exhaled. </p>
<p>And when a nebuliser is used to loosen mucus in the lungs, this mucus could also be exhaled. This could be as particles or coughed out.</p>
<p>So whatever the mechanism, someone with COVID-19 who uses a nebuliser is at risk of inadvertently spreading the virus to others.</p>
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Read more:
<a href="https://theconversation.com/how-the-coronavirus-spreads-through-the-air-5-essential-reads-146735">How the coronavirus spreads through the air: 5 essential reads</a>
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<h2>Don’t we already know this?</h2>
<p>We know that using a nebuliser in COVID-19 patients is not a good idea, especially as many drugs can be delivered in other ways.</p>
<p>For example, the Australian Commission on Safety and Quality in Health Care <a href="https://www.safetyandquality.gov.au/sites/default/files/2020-05/covid-19_-_position_statement_-_nebulisation_and_covid-19_-_28_april_2020.pdf">states</a>:</p>
<blockquote>
<p>Nebulisation is NOT recommended in patients with COVID-19 as it may contribute to the spread of the virus.</p>
</blockquote>
<p>However, it acknowledges that in some circumstances using a nebuliser is unavoidable, for instance, in children.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1359298579026776066"}"></div></p>
<h2>Was a nebuliser responsible for the spread at the Holiday Inn?</h2>
<p>This question is very difficult to answer definitively without making actual measurements.</p>
<p>For example, some so-called <a href="https://www.mja.com.au/journal/2020/213/10/superspreaders-asymptomatics-and-covid-19-elimination">super spreaders</a> are highly contagious. </p>
<p>However, if a COVID-positive person was using a nebuliser, and the spread of the virus was limited to those in relatively close proximity to that person, it is highly likely the nebuliser would have contributed to the spread.</p>
<p>In Sutton’s announcement earlier today, <a href="https://www.abc.net.au/news/2021-02-10/victoria-holiday-inn-covid-quarantine-hotel-to-close/13139224">he said</a> that in the case of transmission at the Holiday Inn, the theory that a nebuliser was the route of infection:</p>
<blockquote>
<p>…makes sense in terms of the geography and it makes sense in terms of the exposure time.</p>
</blockquote>
<h2>So what does this mean for people using nebulisers?</h2>
<p>People using a nebuliser for medical reasons should not be frightened by these developments. They should talk to their health-care provider about any concerns.</p>
<p>The bigger question relates to the use of nebulisers by people in hotel quarantine, which Western Australia says <a href="https://www.abc.net.au/news/2021-02-10/wa-hotel-quarantine-security-guards-to-end-second-jobs-next-week/13139172">it will now ban</a>.</p>
<p>However, it is highly likely a person using a nebuliser in hotel quarantine needs it to provide life-saving medication. So it’s not as simple as banning their use altogether. We’re more likely to see more consideration around how they are used in our quarantine hotels. For example, they might be restricted to particular areas or only used when there is no other medical alternative.</p><img src="https://counter.theconversation.com/content/155032/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brian Oliver receives funding fromThe ARC and the NHMRC. He volunteers his time to the Thoracic Society of Australia and New Zealand. </span></em></p>Nebulisers deliver life-saving medications yet they increase the risk of spreading COVID-19 in hotel quarantine.Brian Oliver, Research Leader in Respiratory cellular and molecular biology at the Woolcock Institute of Medical Research and Professor, Faculty of Science, University of Technology SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1484652020-10-29T13:03:21Z2020-10-29T13:03:21ZDoes coronavirus spread more easily in cold temperatures? Here’s what we know<figure><img src="https://images.theconversation.com/files/366414/original/file-20201029-21-1q87l7l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/blonde-medical-mask-standing-bus-lounge-1686496453">2shrip/Shutterstock</a></span></figcaption></figure><p>Why is the reported number of COVID-19 cases <a href="https://www.ecdc.europa.eu/en/covid-19-pandemic">rising across Europe</a> now? Many countries ended their full lockdowns at the start of the summer, but it wasn’t until the autumn that most places began to see a significant increase in the spread of the virus again. The re-opening of schools and universities led to greater mixing of individuals from different households, but could the fall in outside temperatures also be playing a part?</p>
<p>We know that more people get colds and flu <a href="https://www.hopkinsmedicine.org/health/conditions-and-diseases/winter-illness-guide">in the winter</a> (the colds can be caused by types of coronavirus), but there are several potential reasons for this. It’s often attributed to the fact that people <a href="https://pubmed.ncbi.nlm.nih.gov/23155399/">spend more time indoors</a> when it’s colder, coughing, sneezing and breathing on each other. </p>
<p>You are more likely to choose the option of travelling on a crowded bus or train than walking or cycling to work when the weather is cold and wet. Another theory is that people produce <a href="https://www.theguardian.com/science/2017/feb/15/adding-vitamin-d-to-food-would-reduce-deaths-say-scientists-nhs-study-reduce-risk-respiratory-diseases#:%7E:text=Adding%20vitamin%20D%20to%20food,dangerous%20infections%20such%20as%20pneumonia.">less vitamin D</a> when there is less sunlight and so have weaker immune systems.</p>
<p>However, studies have shown that the annual increase in colds and flu particularly <a href="https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1000316">coincides with</a> when the temperature outside and relative humidity indoors are lower. Flu viruses survive and are transmitted more easily <a href="https://www.bbc.com/future/article/20151016-the-real-reason-germs-spread-in-the-winter">in cold, dry air</a>. So it’s reasonable to think that the <a href="https://www.medrxiv.org/content/10.1101/2020.05.15.20103416v1">same may be true</a> for the COVID-19 coronavirus, SARS-CoV-2, which has a similar size and structure.</p>
<p><a href="http://downloads.hindawi.com/journals/av/2011/734690.pdf?fbclid=iwar2f7-4os677_oeqfau9uu3aus1taa2vlmcp8rg5kzmyfpi-imsva40jnom">Laboratory experiments</a> with coronaviruses and similar viruses have shown that they do not survive well on surfaces when the temperature and relative humidity are high, but comfortable room temperature could be an ideal environment for them to last for several days. And at refrigeration temperatures (4°C) and low relative humidity, they could last <a href="https://aem.asm.org/content/76/9/2712.short">a month or more</a>.</p>
<p>As it happens, there have been repeated reports of outbreaks of COVID among workers in <a href="https://www.bmj.com/content/bmj/370/bmj.m2716.full.pdf">meat-packing factories</a>, which operate under these kind of conditions. However, such factories also contain large numbers of people working close together and shouting to be heard above the noise of machinery, which <a href="https://www.theatlantic.com/ideas/archive/2020/08/wear-your-mask-and-stop-talking/615796/">evidence suggests</a> may be more likely to spread the virus. Their shared <a href="https://www.theguardian.com/environment/2020/jun/22/poor-conditions-in-meat-plants-fuel-covid-19-outbreaks-say-unions">living conditions</a> may also <a href="https://www.bbc.co.uk/news/53137613">encourage transmission</a>.</p>
<figure class="align-center ">
<img alt="Old and young man sat talking outside" src="https://images.theconversation.com/files/366422/original/file-20201029-13-drm60q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/366422/original/file-20201029-13-drm60q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/366422/original/file-20201029-13-drm60q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/366422/original/file-20201029-13-drm60q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/366422/original/file-20201029-13-drm60q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/366422/original/file-20201029-13-drm60q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/366422/original/file-20201029-13-drm60q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Flu viruses are transmitted more easily in cold, dry air.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/senior-father-wheelchair-young-son-on-770413342">Halfpoint/Shutterstock</a></span>
</figcaption>
</figure>
<p>The lessons from the other coronaviruses that have appeared during the 21st century (SARS-CoV and MERS-CoV) also tell a slightly different story. <a href="https://jech.bmj.com/content/59/3/186.short">A study</a> tracking the weather during the 2003 Sars epidemic in China suggested that the peak of the infections occurred during spring-like weather conditions. (There was no way of confirming this through follow-up studies since the virus later died out.)</p>
<p>Regular outbreaks of Mers <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7128823/">also happen</a> in the spring (March to May) in the Middle East. However, this may be less to do with the weather and more related to camel biology. Humans can acquire Mers from each other or from camels. Young camels are a major source of infection and new animals are born during March.</p>
<h2>Southern hemisphere</h2>
<p>We can also look at what happened in the southern hemisphere during winter there. South Africa has reported <a href="https://coronavirus.jhu.edu/map.html">over 700,000</a> cases and experienced a large peak in July, but New Zealand controlled the infection very well and had fewer than 2,000 cases of COVID-19.</p>
<p>These two countries are very different in many respects, so it’s not that useful to directly compare them. But it does seem like the colder weather during July and August was probably not the main factor in deciding their infection rates. New Zealand seems to have kept the spread of SARS-CoV-2 at bay due to geography, the quality of the healthcare system and the effectiveness of the public health response. It might have been able to do that whatever the weather. </p>
<p><a href="https://onlinelibrary.wiley.com/doi/full/10.1111/tbed.13766">Early data</a> from Australia suggested that low humidity would be a factor to look out for and was a better guide to risk of increases in COVID-19 than temperature. However, in Melbourne, there was a large outbreak in July coinciding with a spell of cold weather. This led to a strict lockdown, although it was only fully eased <a href="https://www.bbc.co.uk/news/world-australia-54654646">in October</a>.</p>
<p>In all, it seems like a good idea to be prepared for more COVID-19 cases during the colder months. But the one thing we have learned for sure from SARS-CoV-2 is that new viruses can surprise us. </p>
<p>We also know that coming into close contact with others provides an opportunity for the virus to spread, whatever the weather. So we must keep physical distance between people who do not live in the same household and continue to wear face coverings in enclosed spaces whenever possible. </p>
<p>Unfortunately, we will only learn exactly how changes in the weather affect the pandemic by living through it.</p><img src="https://counter.theconversation.com/content/148465/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sarah Pitt does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Winter weather forces us to congregate inside but evidence suggests cold, dry air also helps spread respiratory viruses.Sarah Pitt, Principal Lecturer, Microbiology and Biomedical Science Practice, Fellow of the Institute of Biomedical Science, University of BrightonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1474392020-10-27T21:29:20Z2020-10-27T21:29:20ZHow to prevent COVID-19 ‘superspreader’ events indoors this winter<figure><img src="https://images.theconversation.com/files/365643/original/file-20201026-19-613zoy.png?ixlib=rb-1.1.0&rect=28%2C0%2C6212%2C4163&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">We've learned much more about the novel coronavirus over the last few months, including that most spreading events occur inddoors.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>The second wave of COVID-19 has arrived. <a href="https://www.express.co.uk/news/world/1315280/Second-wave-coronavirus-map-is-second-wave-happening-Spain-France-Germany-Belgium">Cases are spiking in most European countries</a>, Canada is seeing the number of daily cases <a href="https://www.cnn.com/2020/09/24/americas/canada-trudeau-covid-19-second-wave-intl/index.html">exceed the first peak in April/May</a> and the United States is facing a <a href="https://time.com/5893916/covid-19-coronavirus-third-wave/">potential third wave</a>. </p>
<p>Some countries like Brazil, India and Argentina are still in the <a href="https://www.endcoronavirus.org/countries#action">first wave</a>. Others like New Zealand, Vietnam and Singapore have <a href="https://www.npr.org/sections/goatsandsoda/2020/05/23/861577367/messaging-from-leaders-who-have-tamed-their-countrys-coronavirus-outbreaks">contained the virus</a>. But the second wave has arrived in the northern hemisphere, as we confront the upcoming winter.</p>
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Read more:
<a href="https://theconversation.com/simulations-help-reduce-the-effects-of-a-second-wave-of-covid-19-139798">Simulations help reduce the effects of a second wave of COVID-19</a>
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<p>In most countries, the number of deaths is <a href="https://www.cnn.com/2020/09/24/europe/europe-coronavirus-second-wave-deaths-intl/index.html">lower than in the first wave</a>; we have learned more about the virus and know that the second wave is driven by younger people, which have a lower death rate. Nevertheless, the long-term effects of this wave are yet to be seen.</p>
<p>Mathematical modelling is used to predict the spread of diseases like COVID-19. These models must now take into consideration people’s changing behaviours and the approaching winter.</p>
<h2>Unknown long-term effects</h2>
<p>There is evidence that COVID-19 infection can lead to <a href="https://covid19resources.ca/explained/explained_dbh.html">serious heart problems</a>, which are currently <a href="https://www.sciencemag.org/news/2020/09/evidence-builds-covid-19-can-damage-heart-doctors-are-racing-understand-it">being studied</a>. Some people also experience damage to the <a href="https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/coronavirus-long-term-effects/art-20490351">kidneys, lungs and brain</a>. There have also been reports of <a href="http://dx.doi.org/10.1136/bcr-2020-238419">sudden deafness</a> and “<a href="https://www.nytimes.com/2020/10/11/health/covid-survivors.html">brain fog</a>.” </p>
<p>We still do not know if <a href="https://www.healthline.com/health-news/how-long-does-immunity-last-after-covid-19-what-we-know#What-we-currently-know-about-COVID-19-immunity">there is immunity after infection</a> or whether <a href="http://doi.org/10.1126/science.abe5960">the disease will become endemic</a>. </p>
<p>The second wave might have been triggered by <a href="https://www.thestar.com/news/canada/2020/07/19/lockdown-fatigue-feelings-of-invincibility-may-be-behind-rising-covid-19-infections-in-young-people-scientists-say.html">lockdown fatigue and feelings of invincibility of young population</a>. But <a href="https://www.cnn.com/2020/08/16/health/pandemic-covid-19-denial-mental-health-wellness/index.html">coping mechanisms like denial and rationalism</a>, combined with conflicting public health messages, can lead to <a href="https://www.bloomberg.com/opinion/articles/2020-09-30/covid-19-disobedience-goes-deeper-than-we-think">population disobedience</a> and trigger a large number of cases. </p>
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<figcaption><span class="caption">Al Jazeera investigates the long-term effects of COVID-19.</span></figcaption>
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<h2>Superspreader events</h2>
<p>We have learned important aspects about the spread of COVID-19. The pandemic has largely been driven by <a href="https://www.vox.com/2020/10/2/21498870/white-house-cluster-tested-positive-covid-19-coronavirus">superspreader events</a>, in which a single individual directly infects several contacts. </p>
<p>The reproductive number — known as R0 — of SARS-CoV-2 is between two and three, meaning that, on average, an individual infects between two and three individuals. The variation in the distribution — known as <em>k</em> — has showed that some individuals generate <a href="https://www.theguardian.com/world/2020/jun/01/k-number-what-is-coronavirus-metric-crucial-lockdown-eases">a large number of secondary cases</a>: less than <a href="https://wellcomeopenresearch.org/articles/5-67">20 per cent of individuals produce over 80 per cent of infections</a>.</p>
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Read more:
<a href="https://theconversation.com/r0-how-scientists-quantify-the-intensity-of-an-outbreak-like-coronavirus-and-predict-the-pandemics-spread-130777">R0: How scientists quantify the intensity of an outbreak like coronavirus and predict the pandemic's spread</a>
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</p>
<hr>
<p>There have been numerous examples of superspreader events such as the <a href="https://wwwnc.cdc.gov/eid/article/26/7/20-0764_article">outbreak associated with air conditioning in a restaurant in Guangzhou</a>, China, the exposure of individuals at a <a href="https://www.cdc.gov/mmwr/volumes/69/wr/mm6919e6.htm">choir practice in Skagit County, Wash.</a>, <a href="https://www.usatoday.com/story/news/politics/2020/10/09/anthony-fauci-white-house-held-covid-superspreader-event/5940483002/">the recent Rose Garden ceremony at the White House</a> and a <a href="https://www.thestar.com/news/canada/2020/10/13/patient-zero-displayed-no-symptoms-hamiltons-spinco-superspreader-outbreak-reaches-51-cases.html">spinning class in Hamilton, Ont</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/QufMryuwmrw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The Washington Post analyzes the interactions during the White House Rose Garden ceremony on Sept. 26, after which President Trump and others were diagnosed with COVID-19.</span></figcaption>
</figure>
<h2>The role of aerosols</h2>
<p>We also know that the disease is driven by aerosols, which are small particles made of <a href="https://tinyurl.com/FAQ-aerosols">saliva or respiratory fluid whose size is a few microns</a>. The U.S. Centers for Disease Control and Prevention states that the disease mainly spreads through <a href="https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/how-covid-spreads.html">close contact</a>. They also state that touching contaminated surfaces (known as fomites) is not thought to be a common way that COVID-19 spreads.</p>
<p>Since April, we’ve learned that <a href="https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciaa939/5867798">aerosols and indoor transmission are the main sources of infection</a>. There is evidence that the virus can remain <a href="https://www.docjon.org/post/the-evidence-for-airborne-transmission-of-covid-19-and-why-who-cdc-and-phe-advice-should-change">in the air from 15 minutes up to three hours</a> and transmission indoors may be around <a href="https://www.coloradoan.com/story/news/local/2020/09/18/risk-catching-covid-19-increases-activities-move-indoors-researchers-colorado-state-university-say/5817487002/">20 times higher than outdoors</a>. </p>
<p>Numerous studies show that transmission is due to indoor spreading via aerosols. A recent study of <a href="https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30471-0/fulltext#seccestitle130">1,200 outbreaks</a>, shows that with the exception of two incidents, most outbreaks were indoor and driven by homes and family contacts. </p>
<h2>Paying attention to ventilation</h2>
<p>To help reduce the probability of superspreading events indoors, <a href="https://dx.doi.org/10.1016/S2213-2600(20)30245-9">we need to pay attention to ventilation</a>. Ideally, we should conduct most activities outdoors, but when not possible, air quality should be guaranteed. </p>
<p>Ventilation standards like <a href="https://carleton.ca/covid19/wp-content/uploads/Infection-Prevention-Guidelines-for-Retail-and-Frontline.pdf">ASHRAE and MERV-13 should be mandatory</a>, and when these are not possible, portable air purifiers with HEPA filters <a href="https://www.theatlantic.com/health/archive/2020/07/why-arent-we-talking-more-about-airborne-transmission/614737/">can reduce the probability of infection</a>. </p>
<p>We can also use carbon dioxide detectors to <a href="https://onlinelibrary.wiley.com/doi/abs/10.1034/j.1600-0668.2003.00189.x">check the quality of air indoors</a>. And with the cold weather approaching, controlling <a href="https://passivehouseplus.ie/news/coronavirus/experts-call-for-co2-sensors-as-tool-in-covid-fight">the level of carbon dioxide</a> and humidity indoors can reduce the probability of contagion.</p>
<h2>Simulating behaviours</h2>
<p>My research team works on flexible modelling methodologies that focus on spatial models and can easily be adapted to include the most recent research results.</p>
<p>We built a variety of models to study various aspects of the spread of SARS-CoV-2, including connectivity or mobility factors, mortality rates and interventions. We can study the potential outcomes of complex government policies, such as enforcing the use of masks or physical distancing. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/364358/original/file-20201019-23-j5abmm.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A graph showing the outcome of different measures and behaviours on the spread of COVID-19" src="https://images.theconversation.com/files/364358/original/file-20201019-23-j5abmm.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/364358/original/file-20201019-23-j5abmm.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=416&fit=crop&dpr=1 600w, https://images.theconversation.com/files/364358/original/file-20201019-23-j5abmm.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=416&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/364358/original/file-20201019-23-j5abmm.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=416&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/364358/original/file-20201019-23-j5abmm.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=522&fit=crop&dpr=1 754w, https://images.theconversation.com/files/364358/original/file-20201019-23-j5abmm.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=522&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/364358/original/file-20201019-23-j5abmm.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=522&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Modelling results that show that intermittent lockdowns flatten the curve, but individual disobedience affects the spread rate of the disease.</span>
<span class="attribution"><span class="source">(Román Cárdenas, Gabriel Wainer)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We can also explore mechanisms to combine the base epidemiological models with information about <a href="https://www.youtube.com/watch?v=7zkrVQy45M4">the surrounding environment (buildings, transportation, open spaces)</a>. The influence of the spatial location on the model dynamics can be easily visualized to facilitate more efficient decision-making. </p>
<h2>Simulating environments</h2>
<p>A second aspect of our research investigates how to integrate advanced 3D building models with computer models of how the disease spreads indoors. The research focuses on the spread of viral particles through heating, ventilation and cooling (HVAC) systems in buildings. By studying the effect of <a href="https://www.medicalnewstoday.com/articles/how-humidity-may-affect-covid-19-outcome">humidity levels indoors</a> or the effects of viral particle accumulation in rooms, we can better quantify the risk of COVID-19 and the effectiveness of measures to mitigate the risk. </p>
<p>Our advanced models use carbon dioxide as a proxy for the disease, because the sensors are cheap and sensitive to HVAC systems and room dimensions. These models can help study changes in ventilation, accumulation of viral particles over time and the influence of <a href="https://doi.org/10.1038/s41598-019-38808-z">voice tone levels</a> in a room.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/iLtuyHXCn9I?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Studying the spread of CO2 in an office building.</span></figcaption>
</figure>
<p>These simulations can help to assess the risk of crowded and confined spaces, as well as <a href="https://www.cdc.gov/coronavirus/2019-ncov/php/contact-tracing/contact-tracing-plan/appendix.html#contact">close contacts</a>. </p>
<p>Our next efforts should include modelling long-term side effects and paying attention to individual interactions to study the effects of lockdowns, economic aspects and uncertainty in human behaviour. Advanced tools to <a href="https://arslab.sce.carleton.ca/wp-content/uploads/2020/03/SocialModels.pdf">model these social aspects are needed</a> to identify problems and solutions. Social aspects — including <a href="https://doi.org/10.1038/s41562-020-0884-z">leadership, social environments, stress and coping behaviours</a> — should not be neglected in future research efforts.</p><img src="https://counter.theconversation.com/content/147439/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gabriel Wainer receives funding from NSERC, Solace Inc. and the Department of National Defence, Canada.</span></em></p>As the coronavirus pandemic continues, and the colder weather approaches, new mathematical models are needed to study changing social behaviours and indoor spaces.Gabriel Wainer, Professor, Systems and Computer Engineering, Carleton UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1429882020-07-21T23:33:23Z2020-07-21T23:33:23ZA $200 fine for not wearing a mask is fair, as long as free masks go to those in need<p>As we reach the two-week mark since the <a href="https://www.abc.net.au/news/2020-07-07/victoria-reimposes-lockdown-as-coronavirus-cases-rise/12429990">reinstated restrictions for Melbourne</a>, and are <a href="https://www.abc.net.au/news/2020-07-21/coronavirus-australia-live-news-covid-19-latest-victoria/12474758">yet to see a decline in new daily cases</a>, it is not surprising the Victorian government has now <a href="https://theconversation.com/victorians-and-anyone-else-at-risk-should-now-be-wearing-face-masks-heres-how-to-make-one-141980">made face masks mandatory</a>. </p>
<p>From midnight tonight, residents in metropolitan Melbourne and Mitchell Shire must wear a face covering whenever outside the home, or face a A$200 fine. The state government has also <a href="https://www.abc.net.au/news/2020-07-21/coronavirus-australia-live-news-covid-19-latest-victoria/12474758">ordered 1.37 million reusable masks</a> for public distribution, and says schools will be among the first to receive them. </p>
<p>With some people arguing the measures will unfairly penalise poorer Victorians, Health Minister Jenny Mikakos has <a href="https://www.abc.net.au/news/2020-07-21/coronavirus-australia-live-news-covid-19-latest-victoria/12474758">pledged to provide more information</a> about which groups will also be receiving free masks.</p>
<h2>Will mandatory masks help stop the virus?</h2>
<p>There are certainly many benefits to wearing masks or similar face coverings in <a href="https://www.sciencedirect.com/science/article/pii/S1477893920302301?via%3Dihub">reducing the spread of coronavirus</a>, especially in <a href="https://onlinelibrary.wiley.com/doi/10.1111/irv.12740">closed or confined environments</a>. With rising case numbers and a growing recognition that the coronavirus can be transmitted even without symptoms, numerous health advisory bodies – including the <a href="https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/diy-cloth-face-coverings.html">US Centers for Disease Control and Prevention</a> and the <a href="https://www.who.int/emergencies/diseases/novel-coronavirus-2019/advice-for-public/when-and-how-to-use-masks">World Health Organisation</a> – now recommend masks for the general public. </p>
<p>When it comes to mandatory enforcement of mask wearing, the benefits have to be weighed against other questions, such as whether everyone will be able to obtain masks, and whether the fines unfairly discriminate against people with less money.</p>
<p>Given that even low rates of mask-wearing can <a href="https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3567438">deliver significant benefits</a>, it would be tempting to conclude there is no need for mandatory enforcement. Not all members of the public are likely to embrace the use of face masks equally, so it might make sense simply to rely on those who are more willing.</p>
<p>However, the fact that face masks are cheap (or can be given out for free) and highly effective means the corresponding public health benefits are huge. According to <a href="https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3567438">one US estimate</a>, each additional cloth mask worn by a member of the public would lower the death risk enough to save US$3,000-6,000 in reduced health costs.</p>
<p>Put simply, the more people wear masks, the faster we can potentially resume normal activity. It thus becomes easier to justify stringent measures to deliver universal mask-wearing. The low cost and high effectiveness of masks means even a harsh fine of A$200 becomes justifiable, given the crucial need to suppress COVID-19.</p>
<h2>How much do masks cost?</h2>
<p>The Victorian government has mandated that any type of face-covering material is suitable, meaning residents could potentially minimise their expenses by making their own masks at home. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/348542/original/file-20200721-133010-1xsdgey.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/348542/original/file-20200721-133010-1xsdgey.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/348542/original/file-20200721-133010-1xsdgey.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/348542/original/file-20200721-133010-1xsdgey.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/348542/original/file-20200721-133010-1xsdgey.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/348542/original/file-20200721-133010-1xsdgey.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/348542/original/file-20200721-133010-1xsdgey.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/348542/original/file-20200721-133010-1xsdgey.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">Shovon Bhattacharjee/The Kirby Institute/UNSW</span></span>
</figcaption>
</figure>
<p>One sensible option would be to give free masks to people living in hotspots or who have less financial means – Melbourne’s <a href="https://theconversation.com/nine-melbourne-tower-blocks-put-into-hard-lockdown-what-does-it-mean-and-will-it-work-142033">public housing towers</a> would tick both of these boxes. Free masks could also be given to people who are more likely to use public transport, or who work in jobs that necessitate close contact with the public. </p>
<p>For those buying their own, disposable masks retail for <a href="https://www.chemistwarehouse.com.au/buy/100117/softmed-face-masks-50-pack---new-low-price">about A$1 each</a>, meaning someone who works five days a week would need to spend about A$30 on masks during the six-week lockdown. </p>
<p>Another prudent move would be to prevent stockpiling or profiteering by capping the price (as <a href="https://www.wsj.com/articles/south-korea-rations-face-masks-in-coronavirus-fight-11584283720">South Korea</a> did) or the number of masks that can be purchased at one time (as in <a href="https://www.taiwannews.com.tw/en/news/3912964">Taiwan</a>, which limited purchases to ten masks per person every two weeks) instead of relying on retailers to apply restrictions.</p>
<h2>So why the outrage?</h2>
<p>Some Australians have reacted with anger to the mask mandate, despite widespread community support for other, arguably more disruptive, measures such as social distancing, travel bans and quarantines.</p>
<p>As is clearly evident in the United States, it seems there is something unique about face masks that has many people up in arms. As one Australian Twitter user <a href="https://twitter.com/BridalBizSchool/status/1284823433608486912">wrote</a>: </p>
<blockquote>
<p>Like a good citizen, I’ve stayed home. I’m more than willing to wear a mask publicly indoors but I take my kids for a walk/bike to the park once a day for “FRESH AIR” to relieve some anxiety and stress at government shambles, now he takes the air we breathe?</p>
</blockquote>
<p>After weeks of social distancing and hand sanitising, are face masks simply the straw that broke the camel’s back for some people? One theory, called the <a href="https://journals.sagepub.com/doi/10.1177/1745691617716946">strength model of self-regulation</a>, suggests the more behavioural changes an individual is required to make (such as quitting smoking or refraining from touching their face) the less success they will have at each. </p>
<p>There are many possible explanations for mask refusal: physical discomfort, inconvenience, denial of the benefits, mixed messaging, lack of role modelling, fear of judgement or stigma, or a desire to rebel against authority. But there is little published research on why people might be more willing to accept one disease prevention tactic over another.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/coronavirus-spike-why-getting-people-to-follow-restrictions-is-harder-the-second-time-around-141287">Coronavirus spike: why getting people to follow restrictions is harder the second time around</a>
</strong>
</em>
</p>
<hr>
<p>Public health measures work best when they balance the needs of individuals with those of the public at large. Providing free masks to those who can’t afford them, and trying to understand the points of friction that might make some people less likely to wear them, will both increase the overall levels of mask-wearing.</p>
<p>Mandates and punishments, although justified by public health objectives, can only work for so long. In all likelihood, we will be living with COVID-19 until a vaccine is developed. This means we need sensible and pragmatic strategies to help everyone fight this and future pandemics together.</p><img src="https://counter.theconversation.com/content/142988/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Laura Wall is affiliated with Hunter Medical Research Institute </span></em></p><p class="fine-print"><em><span>Doowon Lee, Francesco Paolucci, Madeleine Hinwood, and Marcello Antonini do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The fines for failing to wear a mask during Melbourne’s lockdown have been criticised as ‘punitive’. But the fact that masks are cheap or free, with huge public health benefits, makes it justifiable.Francesco Paolucci, Professor of Health Economics, University of Bologna, University of NewcastleDoowon Lee, Assistant Dean, International - Strategy and Programs Office PVC - Business and Law, University of NewcastleLaura Wall, Postdoctoral Research Fellow, University of NewcastleMadeleine Hinwood, Research Academic, School of Medicine and Public Health, University of NewcastleMarcello Antonini, PhD, University of NewcastleLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1389252020-05-21T12:22:50Z2020-05-21T12:22:50ZHow to lower your coronavirus risk while eating out: Restaurant advice from an infectious disease expert<figure><img src="https://images.theconversation.com/files/335872/original/file-20200518-83375-1vs4qlm.jpg?ixlib=rb-1.1.0&rect=0%2C6%2C2257%2C1487&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A restaurant in Bangkok created plastic partitions and moved its tables farther apart to separate guests in a normally tight space.</span> <span class="attribution"><a class="source" href="http://gettyimages.com">Lillian Suwanrumpha/AFP/Getty Images</a></span></figcaption></figure><p>As restaurants and bars reopen to the public, it’s important to realize that eating out will increase your risk of exposure to the new coronavirus.</p>
<p>Two of the most important public health measures for keeping illnesses to a minimum are nearly impossible in these situations: First, it’s hard to eat or drink while wearing a face mask. Second, social distancing is difficult in tight spaces normally filled with back-to-back seating and servers who weave among the busy tables all evening long.</p>
<p>So, what should you look out for, and how can you and the restaurant reduce the risk? Here are answers to a few common questions.</p>
<h2>How far apart should tables and bar stools be?</h2>
<p>There is nothing magical about 6 feet, the number we often hear in <a href="https://int.nyt.com/data/documenthelper/6935-CDC-opening-guidelines/e1a8802d0d76b3eb43a8/optimized/full.pdf#page">formal guidance</a> from government agencies. I would consider that the minimum distance required for safe spacing.</p>
<p>The “6-foot” rule is <a href="https://doi.org/10.1001/jama.2020.4756">based on old data about the distance</a> droplets can spread respiratory viruses. These droplets tend to settle out of the air within 6 feet, but that isn’t always the case.<a href="https://arxiv.org/abs/2003.13689v1"> Aerosols can spread the virus</a> <a href="http://doi.org/10.1097/JOM.0000000000000448">over larger distances</a>, though there remains some uncertainty about how common this spread is. <a href="http://doi.org/10.1001/jama.2020.4756">Particles generated by sneezes</a> or <a href="http://www.urbanphysics.net/Social%20Distancing%20v20_White_Paper.pdf">someone running</a> can travel up to 30 feet.</p>
<p><a href="https://doi.org/10.1073/pnas.2006874117">Talking alone has been shown to generate respiratory droplets</a> that could be infectious.</p>
<p>If there is a fan or current generated in a closed space such as a restaurant, particles will also travel farther. This was shown in a paper from China: <a href="http://doi.org/10.3201/eid2607.200764">People in a restaurant downwind of an infected person</a> became infected even though the distance was greater than 6 feet.</p>
<p>The closer the distance and the greater the time someone is exposed to a person who is infectious, the greater the risk.</p>
<h2>If the servers wear masks, is that enough?</h2>
<p>If servers wear masks, that will afford a layer of protection, but customers eating and talking could still spread the virus.</p>
<p>One way to mitigate that risk in this imperfect situation, at least from a public health point of view, would be to have tables surrounded by protective barriers, such as plexiglass or screens, or put tables in separate rooms with doors that can be closed. Some states are encouraging restaurants to <a href="https://www.governor.wa.gov/news-media/inslee-issues-guidance-partially-resuming-dine-restaurant-and-tavern-industry-phase-2">limit each table to only one server</a> who delivers everything.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/335873/original/file-20200518-83352-uegbjw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/335873/original/file-20200518-83352-uegbjw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/335873/original/file-20200518-83352-uegbjw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/335873/original/file-20200518-83352-uegbjw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/335873/original/file-20200518-83352-uegbjw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/335873/original/file-20200518-83352-uegbjw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/335873/original/file-20200518-83352-uegbjw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Guests filled the street seating and balcony at a restaurant on Bourbon Street on May 16, 2020, as New Orleans began lifting some restrictions following two months of closures over the coronavirus.</span>
<span class="attribution"><a class="source" href="http://gettyimages.com">Claire Bangser/AFP/Getty Images</a></span>
</figcaption>
</figure>
<p>Restaurants could also screen guests before they enter, either with temperature checks or questions about symptoms and their close contacts with anyone recently diagnosed with COVID-19. It’s controversial, but <a href="https://www.ocregister.com/2020/03/07/in-response-to-coronavirus-fears-restaurant-checks-customers-temperatures-at-the-door/">restaurants in California have tried it</a>. Washington state tried to require restaurants to <a href="https://www.seattletimes.com/life/food-drink/inslee-retracts-requirement-that-diners-provide-contact-info-to-be-able-to-dine-at-restaurants/">record visitors’ contact information</a> in case an outbreak is discovered, but it pulled back to only recommend doing so.</p>
<p>It’s easier to screen employees. In fact, <a href="https://www.cdc.gov/coronavirus/2019-ncov/downloads/community/restaurants-and-bars-decision-tree.pdf">guidelines from the Centers for Disease Control and Prevention</a> recommend restaurants have employee screening in place before they reopen. But while screening employees for possible infection could decrease risk, it’s important to remember that people <a href="http://doi.org/10.1001/jamainternmed.2020.2020">can be infectious six days</a> before they develop symptoms. That is why masks, eye protection, social distancing and hand hygiene are critical measures for preventing infection.</p>
<h2>Should I ask for disposable utensils and wipe everything down?</h2>
<p>Regular dishwashing of plates, glasses and utensils, and laundering of napkins and tablecloths, will inactivate the virus. No need for disposables here.</p>
<p>The table should also be cleaned and disinfected between uses and marked as sanitized.</p>
<p>Menus are a bit more problematic, depending on the material. Plastic menus could be disinfected. Disposable menus would be more ideal. Remember, even if someone touches a surface that has infectious virus, as long as they don’t touch their mouth, nose or eyes they should be safe. So, when in doubt, wash your hands or use hand sanitizer.</p>
<h2>Can I get the virus from food from the kitchen?</h2>
<p>The risk of becoming infected with the new coronavirus from food is very low.</p>
<p>This is a respiratory virus whose primary mode of infection is accessing the upper or lower respiratory tract through droplets or aerosols entering your mouth, nose or eyes. It needs to enter the respiratory tract to cause infection, and it cannot do this by way of the stomach or intestinal tract.</p>
<p>The virus also is not very stable in the environment. Studies have shown it <a href="http://doi.org/10.1056/NEJMc2004973">loses half its viral concentration</a> after less than an hour on copper, three and a half hours on cardboard and just under seven hours on plastic. If food were to be contaminated during preparation, <a href="https://doi.org/10.1101/2020.04.11.036855">cooking temperature would likely inactivate</a> much if not all of the virus.</p>
<p>The use of masks and maintaining good hand hygiene by food preparers should significantly reduce the risk of food contamination. </p>
<h2>Is outdoor seating or a drive-through any safer?</h2>
<p>Vulnerable people may want to pass on dine-in options and focus on pickup or perhaps outside dining if the conditions are appropriate.</p>
<p>Drive-up windows or carry-out are probably the safest; transient interaction with one individual when everyone is wearing masks is a lower-risk situation.</p>
<p>Overall, outside dining is safer than indoor dining with everything else being equal on a nonwindy day due to the larger air volume. Maintaining eye protection via glasses and intermittent mask use between bites and sips would further decrease the risk.</p>
<hr>
<p><em>You might also be interested in other parts of this series:</em></p>
<ul>
<li><a href="https://theconversation.com/how-do-you-stay-safe-now-that-states-are-reopening-an-expert-explains-how-to-assess-risk-when-reconnecting-with-friends-and-family-138518">How do you stay safe now that states are reopening? An expert explains how to assess risk when reconnecting with friends and family</a></li>
<li><a href="https://theconversation.com/heres-how-to-stay-safe-while-buying-groceries-amid-the-coronavirus-pandemic-138683">Here’s how to stay safe while buying groceries amid the coronavirus pandemic</a></li>
<li><a href="https://theconversation.com/how-can-you-be-safe-at-a-pool-the-beach-or-a-park-a-doctor-offers-guidance-as-coronavirus-distancing-measures-lifted-138771">How can you be safe at pools, beaches or parks? A doctor offers guidance as coronavirus distancing measures lifted</a></li>
<li><a href="https://theconversation.com/should-you-fly-yet-an-epidemiologist-and-an-exposure-scientist-walk-you-through-the-decision-process-138782">Should you fly yet? An epidemiologist and an exposure scientist walk you through the decision process</a></li>
</ul>
<p>[<em>The Conversation’s newsletter explains what’s going on with the coronavirus pandemic. <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=upper-coronavirus-daily">Subscribe now</a>.</em>]</p><img src="https://counter.theconversation.com/content/138925/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Thomas A. Russo does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>It’s hard to eat while wearing a face mask, and social distancing isn’t easy in restaurants’ normally tight quarters. An infectious disease expert offers some tips on what to look for to stay safe.Thomas A. Russo, Professor and Chief, Infectious Disease, Jacobs School of Medicine and Biomedical Sciences, University at BuffaloLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1385182020-05-18T12:20:10Z2020-05-18T12:20:10ZHow do you stay safe now that states are reopening? An expert explains how to assess risk when reconnecting with friends and family<figure><img src="https://images.theconversation.com/files/335566/original/file-20200517-138624-1q9vcye.jpg?ixlib=rb-1.1.0&rect=18%2C63%2C6031%2C3854&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">People shop at the reopening of the Farmer's Market in Manhattan Beach, California on May 12, 2020.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/lindsay-wandzilak-center-from-manhattan-beach-with-daughter-news-photo/1212894004?adppopup=true">Jay L. Clendenin/Los Angeles Times via Getty Images</a></span></figcaption></figure><p><em>Editor’s note: Now that states are <a href="https://www.nytimes.com/interactive/2020/us/states-reopen-map-coronavirus.html">relaxing</a> social distancing restrictions, people desperately want to see friends and family, go to a restaurant and let our kids have playdates. Even grocery shopping sounds fun. But how can you do that and still stay safe? Here, an epidemiologist who is immune-compromised himself walks you through some decision-making.</em></p>
<p>The Centers for Disease Control and Prevention has finally released new guidelines for <a href="https://www.cdc.gov/coronavirus/2019-ncov/downloads/community/workplace-decision-tree.pdf">businesses</a>, <a href="https://www.cdc.gov/coronavirus/2019-ncov/downloads/community/restaurants-and-bars-decision-tree.pdf">bars</a> and <a href="https://www.cdc.gov/coronavirus/2019-ncov/community/schools-childcare/Schools-Decision-Tree.pdf">schools</a> that are considering reopening. Although following these guidelines should help, it’s frustrating there hasn’t been more clear, concise communication about the risk of infection. And without strict guidelines, it will be up to us to minimize our own risk and the risk of everyone around us. </p>
<p>In large part, this is because there is still so much we scientists and physicians don’t know about the new coronavirus. The pace of new research on the virus, SARS-CoV-2, and the disease it causes, COVID-19, is truly astonishing. There are also times when the science and the necessity of the moment are in conflict; a prime example is the confusion about using face masks while a worldwide shortage of personal protective equipment exists.</p>
<p>And the pattern of disease is extremely localized. Michigan’s outbreak looks different from Iowa’s, which looks different from Colorado’s. Even within states, outbreaks are very distinct. The outbreak I’m experiencing in <a href="https://covidmapping.org/">southeast Michigan</a> is not like the one my grandparents are experiencing two hours north of here. <a href="https://scholar.google.com/citations?user=e9oZqAgAAAAJ&hl=en">As a research scientist</a>, I study herd immunity and vaccine effectiveness. As we slowly begin to return to normal life – albeit a new normal – I can tell you there are ways we can minimize our risk. </p>
<p>As a survivor of leukemia and a bone marrow transplant, I am part of a <a href="https://www.cdc.gov/coronavirus/2019-ncov/need-extra-precautions/groups-at-higher-risk.html">high-risk population</a>, so my risk calculation is likely different from yours. As my state starts to relax restrictions, I will continue to limit my interactions with others as much as I can. Here are things you can consider.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/should-we-wear-masks-or-not-an-expert-sorts-through-the-confusion-135135">Should we wear masks or not? An expert sorts through the confusion</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/335456/original/file-20200515-138610-102pm2v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/335456/original/file-20200515-138610-102pm2v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/335456/original/file-20200515-138610-102pm2v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/335456/original/file-20200515-138610-102pm2v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/335456/original/file-20200515-138610-102pm2v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/335456/original/file-20200515-138610-102pm2v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/335456/original/file-20200515-138610-102pm2v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">California has allowed some retail businesses to reopen, including car dealerships, clothing stores and bookstores. Here, people appear to pass close in the flower district of Los Angeles.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/people-pass-close-to-one-another-as-businesses-in-the-news-photo/1212203517?adppopup=true">Getty Images / David McNew</a></span>
</figcaption>
</figure>
<h2>What’s associated with a high risk of transmission?</h2>
<p>How SARS-CoV-2 <a href="https://science.sciencemag.org/content/368/6491/eabb6936.abstract">transmits</a> from person to person is still a mystery. It can certainly be transmitted by large <a href="http://dx.doi.org/10.1016/S1473-3099(20)30113-4">respiratory droplets</a>, like those produced when we cough or sneeze. Evidence also suggests that <a href="https://theconversation.com/coronavirus-drifts-through-the-air-in-microscopic-droplets-heres-the-science-of-infectious-aerosols-136663">smaller aerosol particles</a>, spread while talking or breathing, can lead to transmission. There is some <a href="https://wwwnc.cdc.gov/eid/article/26/7/20-1595_article">evidence</a> that people can transmit the virus before they have symptoms, although they will likely have the <a href="https://www.nature.com/articles/s41591-020-0869-5">highest amount of virus</a> close to the start of the illness. </p>
<p>Taking all this together, it’s safe to say the riskiest thing you can do is to come into close contact with sick people. That’s why the advice about self-isolation <a href="https://www.cdc.gov/coronavirus/2019-ncov/if-you-are-sick/index.html">if you feel ill</a> is so important.</p>
<p>It’s also becoming clear the virus transmits most effectively in indoor settings. There, close contact between infected people and inadequate ventilation are more likely. The infection risk is especially high among <a href="https://www.medrxiv.org/content/10.1101/2020.04.11.20056010v1">household contacts</a>. Efficient transmission in crowded, enclosed spaces also explains the high attack rates in <a href="https://www.cdc.gov/mmwr/volumes/69/wr/mm6913e1.htm">nursing homes</a>, <a href="https://www.cidrap.umn.edu/news-perspective/2020/04/us-food-processing-plants-become-covid-19-hot-spots">food processing plants,</a> <a href="http://jamanetwork.com/article.aspx?doi=10.1001/jamainternmed.2020.1856">jails and prisons</a> and cruise ships. On the flip side, the risk of transmission does seem to be <a href="https://www.medrxiv.org/content/10.1101/2020.04.04.20053058v1">lower</a> outdoors. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/335578/original/file-20200517-138624-18j8rkp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/335578/original/file-20200517-138624-18j8rkp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/335578/original/file-20200517-138624-18j8rkp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/335578/original/file-20200517-138624-18j8rkp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/335578/original/file-20200517-138624-18j8rkp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/335578/original/file-20200517-138624-18j8rkp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/335578/original/file-20200517-138624-18j8rkp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">People experience outdoor dining at a restaurant in Cincinnati, Ohio on May 15, 2020 as businesses began to reopen.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/customers-experience-outdoor-dining-at-taste-of-belgium-as-news-photo/1213156037?adppopup=true">Jason Whitman/NurPhoto via Getty Images</a></span>
</figcaption>
</figure>
<h2>How do we minimize risk?</h2>
<p>If the riskiest thing is to be in a crowd while indoors with sick people, then it follows the least risky behavior is to be in small groups, outdoors and to avoid sick people.</p>
<p>I think it will help to describe a simple model of infectious disease. The rate of new infections over a given time period is called the “force of infection,” which depends on a few things: the rate at which people contact each other; the probability of infection given contact; and the number of infectious individuals in a population. </p>
<p>This means our ability to prevent new infections depends on two things: reducing the rate at which people contact each other – or reducing the probability of infection given contact. </p>
<p>Reducing the contact rate was the goal of stay-at-home measures. By all accounts, this is still the most effective tool to prevent new infections. </p>
<p>Other nonpharmaceutical interventions, like face masks and hand hygiene, reduce the effective contact, or the chance the virus is transmitted if there is contact. <a href="https://theconversation.com/masks-help-stop-the-spread-of-coronavirus-the-science-is-simple-and-im-one-of-100-experts-urging-governors-to-require-public-mask-wearing-138507">Universal masking</a> may be <a href="https://arxiv.org/pdf/2004.13553.pdf">particularly effective</a> if we can’t rely on symptomatic screening for identifying infectious cases. </p>
<p>Or maybe you’ve heard of the <a href="https://www.statnews.com/2020/04/24/swiss-cheese-approach-second-chance-contain-covid-19/">layers of Swiss cheese</a>. Sometimes you have a few interventions (slices of Swiss cheese), but none is perfect (the holes). But stack the slices up, and the holes start to cover up. Layering imperfect interventions can, in a similar way, slow down transmission. </p>
<h2>So what does it all mean?</h2>
<p>I once read a quote about the common cold from Ian Mackay, an Australian virologist: “The only fail-safe means of avoiding a cold is to live in complete isolation from the rest of humanity.” The same is probably true for COVID-19. </p>
<p>But that’s not realistic. Authorities should borrow ideas from HIV prevention and focus on clear messages for <a href="https://www.theatlantic.com/ideas/archive/2020/05/quarantine-fatigue-real-and-shaming-people-wont-help/611482/">harm reduction</a>. In the absence of stay-at-home orders, all of us will have to decide for ourselves how much risk we are willing to tolerate.</p>
<p>I’m a leukemia survivor, so I will factor that in. You, too, will need to consider your medical history. When I’m not in isolation, I will stack as many layers of Swiss cheese as I can to minimize any risk: staying 6-10 feet away from others, wearing masks, staying outdoors.</p>
<p>I think these are generally common-sense guidelines for anyone. </p>
<ul>
<li><p>If your local authorities allow small gatherings, then getting together with friends who aren’t sick or who haven’t been in contact with other sick people is safest outdoors. </p></li>
<li><p>Try to stay as far apart from each other as you can.</p></li>
<li><p>Keep a mask and hand sanitizer nearby. </p></li>
<li><p>Don’t share food or drinks.</p></li>
<li><p>If anyone feels sick or has had recent contact with someone who feels sick, they should skip the playdate (this goes for adults and kids).</p></li>
<li><p>If you are seeing someone at high risk of severe disease, an older relative or someone with a compromised immune system, take even more precautions and consider whether you can connect with them virtually. </p></li>
</ul>
<p>[<em>You’re too busy to read everything. We get it. That’s why we’ve got a weekly newsletter.</em> <a href="https://theconversation.com/us/newsletters/weekly-highlights-61?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=weeklybusy">Sign up for good Sunday reading.</a> ]</p><img src="https://counter.theconversation.com/content/138518/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ryan Malosh receives salary support from the Centers for Disease Control and Prevention (CDC) and the National Institute for Allergy and Infectious Disease (NIAID). </span></em></p>The US is slowly reopening, but the messages from governments are confusing. An expert offers guidance on many people’s first priority – connecting with loved ones.Ryan Malosh, Assistant Research Scientist, University of MichiganLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1345912020-04-03T13:27:31Z2020-04-03T13:27:31ZCoronavirus is growing exponentially – here’s what that really means<figure><img src="https://images.theconversation.com/files/324290/original/file-20200331-65514-1p346ra.jpg?ixlib=rb-1.1.0&rect=0%2C72%2C5367%2C3476&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/exponential-growth-curve-explained-on-blackboard-543765145">marekuliasz/Shutterstock</a></span></figcaption></figure><p>You may have seen a version of the infographic (below) that explains the potential impact of social distancing. It nicely illustrates that reducing the total number of disease-spreading contacts each infected person has can have a dramatic effect on the total number of infections a short time later. The numbers rely on the mathematical concept of “exponential growth”.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/368847/original/file-20201111-15-jis72m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/368847/original/file-20201111-15-jis72m.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/368847/original/file-20201111-15-jis72m.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/368847/original/file-20201111-15-jis72m.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/368847/original/file-20201111-15-jis72m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/368847/original/file-20201111-15-jis72m.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/368847/original/file-20201111-15-jis72m.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Exponential growth total.</span>
<span class="attribution"><span class="source">Adapted from an infographic created by Robert Signer and Gary Warshaw University of California San Diego.</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Recently, Boris Johnson, the British prime minister, <a href="https://www.theguardian.com/politics/live/2020/mar/16/boris-johnson-press-conference-coronavirus-live-firms-could-soon-be-allowed-to-run-reduced-services-because-of-coronavirus-shapps-suggests-politics-live">told the press</a> that “it looks as though we’re now approaching the fast growth part of the upward curve. And without drastic action, cases could double every five or six days”. The consistent doubling of cases in a fixed period is the hallmark of exponential growth. </p>
<p>The number of new infections that a single infectious individual will cause during their infectious period is known as the basic reproduction number of a disease. This number is key to <a href="https://theconversation.com/how-to-model-a-pandemic-134187">determining how widespread</a> a disease will become.</p>
<p>For COVID-19, early estimates of the basic reproduction number have it <a href="https://www.lshtm.ac.uk/newsevents/news/2020/preliminary-analysis-transmission-and-control-new-coronavirus">somewhere between 1.5 and 4</a>. The infographic assumes a figure somewhere in the middle, at 2.5 infectious contacts per infectious individual.</p>
<p>If the reproduction number of a disease can be brought below one, then the spread will slow until the disease dies out. The revised infographic below shows the number of currently infected people. Reducing contact with others by 75% will bring the reproduction number below the critical level, allowing the number of infected people to decrease almost to zero in just two months.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/368849/original/file-20201111-15-r2x46g.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/368849/original/file-20201111-15-r2x46g.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/368849/original/file-20201111-15-r2x46g.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/368849/original/file-20201111-15-r2x46g.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/368849/original/file-20201111-15-r2x46g.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/368849/original/file-20201111-15-r2x46g.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/368849/original/file-20201111-15-r2x46g.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Exponential growth, current.</span>
<span class="attribution"><span class="source">Adapted from an infographic created by Robert Signer and Gary Warshaw University of California San Diego</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>However, the basic reproduction number of the current stage of the outbreak is way above one. This means that each newly infected person will pass on the disease to at least one more person, on average, and consequently the disease will take off exponentially.</p>
<h2>What exponential growth is</h2>
<p>But what, precisely, is exponential growth? The mathematical definition says that a quantity that increases with a rate proportional to its current size will grow exponentially. This means that as the quantity increases so does that rate at which it grows. The more infected people we have in the early stages of a disease outbreak, the more people they will infect and the more the cases will rise.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/323986/original/file-20200330-146705-8vuq4p.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/323986/original/file-20200330-146705-8vuq4p.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/323986/original/file-20200330-146705-8vuq4p.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/323986/original/file-20200330-146705-8vuq4p.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/323986/original/file-20200330-146705-8vuq4p.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/323986/original/file-20200330-146705-8vuq4p.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=532&fit=crop&dpr=1 754w, https://images.theconversation.com/files/323986/original/file-20200330-146705-8vuq4p.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=532&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/323986/original/file-20200330-146705-8vuq4p.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=532&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The total number of confirmed cases of COVID-19 in the UK is increasing exponentially.</span>
<span class="attribution"><span class="source">Max Roser, Hannah Ritchie and Esteban Ortiz-Ospina (2020) - 'Coronavirus Disease (COVID-19) – Statistics and Research', CC BY</span></span>
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<p>Other situations in which exponential growth plays a critical role range from pyramid schemes to nuclear weapons. In a pyramid scheme, each new investor invites two more recruits who in turn invite two more. This rapid growth, at a rate proportional to the current number of members, inevitably leads to a situation in which there aren’t enough new recruits to keep the scheme going and it eventually collapses. When the pyramid tumbles, most investors lose their money. </p>
<p>In a nuclear fission bomb, a single uranium atom splits in two, jettisoning fast-moving neutrons and large quantities of energy in the form of electromagnetic radiation. The neutrons then collide with more atomic nuclei, splitting more atoms and releasing yet more energy in a nuclear chain reaction that increases exponentially. </p>
<p>At about 8:15 in the morning of August 6 1945, the atomic bomb known as the Little Boy detonated releasing energy equivalent to 30 million sticks of dynamite in an instant, devastating the Japanese city of Hiroshima. The surrender of Imperial Japan was announced nine days later. This is the awesome power of exponential growth.</p>
<h2>What exponential growth isn’t</h2>
<p>Although the concept of exponential growth is not new in the public consciousness, a lot of misconceptions surround the idea. Exponential is often <a href="https://studiousguy.com/real-life-examples-exponential-growth/">used as a byword for rapid or large</a>. As a counterpoint, consider the money in your bank account. Provided the interest is compounded (that is, interest is added to your initial amount and earns interest itself) then the total amount of money in your account increases in proportion to its current size – the hallmark of exponential growth. </p>
<p>As Benjamin Franklin put it: “Money makes money, and the money that money makes, makes more money.” If you could wait long enough, even the smallest investment would become a fortune. But don’t lock up your rainy-day fund just yet. If you invested £100 at 1% per year it would take you over 900 years to become a millionaire. Very few people would accuse the exponential growth associated with their bank account of being large or rapid.</p>
<p>So exponential growth does not necessarily deal with big quantities, and it is not necessarily fast. Unfortunately, across a wide range of different countries, the term exponential is appropriate to describe the rapid spread of SARS-CoV-2, the virus that causes COVID-19. With <a href="https://www.bbc.co.uk/news/health-52056111">cases doubling every three to four days in the UK and deaths doubling every two to three days</a>, things could get ugly quickly.</p>
<h2>Small comfort</h2>
<p>One small crumb of comfort is that almost nothing can grow exponentially forever. The only exception, ironically, is the all-too-slow growth of money in your bank account, which, at least on paper, could grow indefinitely. Unfortunately, COVID-19 cases don’t have to grow exponentially forever, or even for much longer, before the disease becomes one of the most devastating pandemics the world has ever seen. </p>
<p>Because the exponential proliferation of the disease is so undeniably dramatic, any changes we can make at this relatively early stage can make a huge difference even a few days down the line. Now is the time to act, to “double down” on our containment efforts to bring the exponential spread under control.</p><img src="https://counter.theconversation.com/content/134591/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christian Yates does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The awesome power of exponential growth explained.Christian Yates, Senior Lecturer in Mathematical Biology, University of BathLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1342382020-03-27T02:33:50Z2020-03-27T02:33:50ZCitizen science: how you can contribute to coronavirus research without leaving the house<figure><img src="https://images.theconversation.com/files/323443/original/file-20200326-132995-18x7af6.jpg?ixlib=rb-1.1.0&rect=36%2C36%2C6071%2C3617&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption"></span> </figcaption></figure><p>As Australians try to <a href="https://www.beyondblue.org.au/the-facts/looking-after-your-mental-health-during-the-coronavirus-outbreak">maintain social engagement during self-isolation</a>, <a href="https://citizenscience.org.au/">citizen science</a> offers a unique opportunity. </p>
<p>Defined as “public participation and collaboration in scientific research”, citizen science allows everyday people to use technology to unite towards a common goal – from the comfort of their homes. And it is now offering a chance to <a href="http://eu-citizen.science/citizen-science-resources-related-to-the-covid19-pandemic/">contribute to research on the coronavirus pandemic</a>.</p>
<p>With so many of us staying home, this could help build a sense of community where we may otherwise feel <a href="https://www.lifeline.org.au/get-help/topics/mental-health-and-wellbeing-during-the-coronavirus-covid-19-outbreak">helpless</a>, or <a href="https://www.beyondblue.org.au/the-facts/looking-after-your-mental-health-during-the-coronavirus-outbreak">struggle with isolation</a>. </p>
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Read more:
<a href="https://theconversation.com/cant-sleep-and-feeling-anxious-about-coronavirus-youre-not-alone-134407">Can't sleep and feeling anxious about coronavirus? You're not alone</a>
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<p>Anyone is welcome to contribute. You don’t need expertise, just time and interest. Projects exist in many forms, catering to people of diverse ages, backgrounds and circumstances. Many projects offer resources and guides to help you get started, and opportunities to collaborate via online discussion forums.</p>
<h2>Ditch the news cycle – engage, gain skills and make a difference</h2>
<p>Scientists worldwide are racing to find effective treatments and vaccines to halt the coronavirus pandemic. As a citizen scientist, you can join the effort to help tackle COVID-19, and other infectious diseases.</p>
<p><a href="https://fold.it/">Foldit</a> is an online game that challenges players to fold proteins to better understand their structure and function. The Foldit team is now challenging citizen scientists to design antiviral proteins that can bind with the coronavirus. </p>
<p>The highest scoring designs will be manufactured and tested in real life. In this way, Foldit offers a creative outlet that could eventually contribute to a future vaccine for the virus. </p>
<p>Another similar project is <a href="https://www.howtogeek.com/663539/how-to-fight-coronavirus-with-foldinghome-and-a-gaming-pc/">Folding@home</a>. This is a distributed computing project that, rather than using you to find proteins, uses your computer’s processing power to run calculations in the background. Your computer becomes one of thousands running calculations, all working together.</p>
<p>One way to combat infectious diseases is by monitoring their spread, to predict outbreaks. </p>
<p>Online surveillance project <a href="https://info.flutracking.net/">FluTracking</a> helps track influenza. By completing a 10-second survey each week, participants aid researchers in monitoring the prevalence of flu-like symptoms across Australia and New Zealand. It could also <a href="https://www.newcastleherald.com.au/story/6646474/flutracking-needs-community-support-to-help-track-any-potential-coronavirus-outbreaks/">help track the spread of the coronavirus</a>.</p>
<p>Such initiatives are increasingly important in the global fight against emerging infectious diseases, including COVID-19. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/321865/original/file-20200320-22594-1u28cxp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/321865/original/file-20200320-22594-1u28cxp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/321865/original/file-20200320-22594-1u28cxp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=467&fit=crop&dpr=1 600w, https://images.theconversation.com/files/321865/original/file-20200320-22594-1u28cxp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=467&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/321865/original/file-20200320-22594-1u28cxp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=467&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/321865/original/file-20200320-22594-1u28cxp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=587&fit=crop&dpr=1 754w, https://images.theconversation.com/files/321865/original/file-20200320-22594-1u28cxp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=587&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/321865/original/file-20200320-22594-1u28cxp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=587&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Citizen science portal Flutracking’ was designed to allow researchers and citizens to track flu-like symptoms around Australia and New Zealand.</span>
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<p>Another program, <a href="https://www.patientslikeme.com/conditions">PatientsLikeMe</a>, empowers patients who have tested positive to a disease to share their experiences and treatment regimes with others who have similar health concerns. This lets researchers test potential treatments more quickly. </p>
<p>The program recently set up a <a href="https://www.patientslikeme.com/conditions/COVID-19">community for people who have contracted COVID-19 and recovered</a>. These individuals are contributing to a data set that could prove useful in the fight against the virus.</p>
<h2>Environmental projects need your support too</h2>
<p>If you’d like to get your mind off COVID-19, there’s a plethora of other options for citizen scientists. You can contribute to conservation and nature recovery efforts – <a href="https://www.theguardian.com/australia-news/2020/jan/31/birds-insects-animal-poo-citizen-science-search-for-data-to-make-sense-of-bushfire-devastation">a task many took to after the recent bushfires</a>. </p>
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Read more:
<a href="https://theconversation.com/coronavirus-seven-ways-collective-intelligence-is-tackling-the-pandemic-133553">Coronavirus: seven ways collective intelligence is tackling the pandemic</a>
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<p>Some sites ask volunteers to digitise data from ongoing environmental monitoring programs. Contributors need no prior experience, and interpret photos taken with remote digital cameras using online guides. One example is Western Australia’s Western Shield <a href="https://www.zooniverse.org/projects/birgus2/western-shield-camera-watch">Camera Watch</a>, available through <a href="https://www.zooniverse.org/">Zooniverse</a>.</p>
<p>Other sites crowdsource volunteers to transcribe data from natural history collections (<a href="https://australianmuseum.net.au/get-involved/citizen-science/digivol/">DigiVol</a>), historical logbooks from explorers, and weather observation stations (<a href="https://www.zooniverse.org/projects/drewdeepsouth/southern-weather-discovery">Southern Weather Discovery</a>).</p>
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<img alt="" src="https://images.theconversation.com/files/322507/original/file-20200324-155624-1hhi2vs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/322507/original/file-20200324-155624-1hhi2vs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1046&fit=crop&dpr=1 600w, https://images.theconversation.com/files/322507/original/file-20200324-155624-1hhi2vs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1046&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/322507/original/file-20200324-155624-1hhi2vs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1046&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/322507/original/file-20200324-155624-1hhi2vs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1315&fit=crop&dpr=1 754w, https://images.theconversation.com/files/322507/original/file-20200324-155624-1hhi2vs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1315&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/322507/original/file-20200324-155624-1hhi2vs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1315&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The Cornell Lab of Ornithology’s citizen science app eBird uses bird sightings to fuel research and conservation efforts.</span>
<span class="attribution"><span class="source">eBird</span></span>
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<p>Citizen science programs such as <a href="https://www.allaboutbirds.org/news/how-to-make-these-next-few-weeks-a-little-easier-courtesy-of-birds/">eBird</a>, BirdLife Australia’s <a href="https://birdata.birdlife.org.au/">Birdata</a>, the Australian Museum’s <a href="https://www.frogid.net.au/">FrogID</a>, <a href="https://www.climatewatch.org.au/">ClimateWatch</a>, <a href="https://questagame.com/">QuestaGame</a>, <a href="https://naturemapr.org/">NatureMapr</a>, and the <a href="https://nespurban.edu.au/platforms/caul-urban-wildlife-app/">Urban Wildlife App</a>, all have freely available mobile applications that let you contribute to <a href="https://www.ala.org.au/">“big” databases</a> on urban and rural wildlife. </p>
<p>Nature watching is a great self-isolation activity because you can do it anywhere, including at home. <a href="https://questagame.com/">Questagame</a> runs a series of “bioquests” where people of all ages and experience levels can photograph animals and plants they encounter. </p>
<p>In April, we’ll also have the national <a href="https://wildpollinatorcount.com/">Wild Pollinator Count</a>. This project invites participants to watch any flowering plant for just ten minutes, and record insects that visit the flowers. The aim is to boost knowledge on wild pollinator activity. </p>
<p>The data collected through citizen science apps are used by researchers to explore animal migration, understand ranges of species, and determine how changes in climate, air quality and habitat affect animal behaviour.</p>
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Read more:
<a href="https://theconversation.com/as-heat-strikes-heres-one-way-to-help-fight-disease-carrying-and-nuisance-mosquitoes-128466">As heat strikes, here's one way to help fight disease-carrying and nuisance mosquitoes</a>
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<p>This year for the first time, several Australian cities are participating in iNaturalist’s <a href="https://citynaturechallengeaustralia.wordpress.com/">City Nature Challenge</a>. The organisers have adapted planned events with COVID-19 in mind, and suggest ways to document nature while maintaining social distancing. You can simply capture what you can see in your backyard, or when taking a walk, or put a moth light out at night to see what it attracts.</p>
<h2>Connecting across generations</h2>
<p>For those at home with children, there are a variety of projects aimed at younger audiences. </p>
<p>From <a href="https://astroquest.net.au/">surveying galaxies</a> to the Bird Academy Play Lab’s <a href="https://academy.allaboutbirds.org/learning-games/#_ga=2.235486017.1755083873.1584592553-131672438.1584592553">Games Powered By Birds</a> - starting young can encourage a lifetime of learning.</p>
<p>If you’re talented at writing or drawing, why not keep a nature diary, and share your observations through a <a href="https://mynaturediaries.wordpress.com/blog/">blog</a>.</p>
<p>By contributing to research through digital platforms, citizen scientists offer a repository of data experts might not otherwise have access to. The <a href="https://citizenscience.org.au/2020/03/21/citizen-science-and-covid-19/">Australian Citizen Science Association (ACSA) website</a> has details on current projects you can join, or how to start your own. </p>
<p>Apart from being a valuable way to pass time while self-isolating, citizen science reminds us of the importance of community and collaboration at a time it’s desperately needed.</p><img src="https://counter.theconversation.com/content/134238/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ayesha Tulloch receives funding from the Australian Research Council and the NSW Government's Department of Planning, Industry and Environment. She is the Vice President of Public Policy and Outreach and co-convenes the Science Communication Chapter for the Ecological Society of Australia, and sits on Birdlife Australia's Research and Conservation Committee. She is a member of eBird Australia and the University of Sydney's Charles Perkins Centre Citizen Science Node.</span></em></p><p class="fine-print"><em><span>Aaron Greenville receives funding from the Australian Research Council, National Landcare Program, Herman Slade Foundation, National Environmental Science Programme and a Sydney Life Grant from the University of Sydney. He is a founding member of Team Kowari, a not-for-profit organisation dedicated to the conservation of the kowari and member of Charles Perkins Centre Citizen Science Node. </span></em></p><p class="fine-print"><em><span>Alice Motion receives funding from the Westpac Scholars Foundation and the Google Impact Challenge. She works at the School of Chemistry at the University of Sydney where she is Co-Chair of the Citizen Science Node situated in the Charles Perkins Centre and Deputy Director (Outreach) of the Sydney Nano Institute. The University of Sydney is the host organisation of the Australian Citizen Science Association (ACSA) and Alice is a member of the ACSA management committee. </span></em></p><p class="fine-print"><em><span>Cobi Calyx works for the Centre for Social Impact, UNSW Sydney, with funding from UNSW Science and the Australian Academy of Science through Future Earth Australia. She was a founding member and is now a Committee Member of the Australian Citizen Science Association.</span></em></p><p class="fine-print"><em><span>Glenda Wardle receives funding from the Australian Research Council, Herman Slade Foundation, Central Land Council, National Landcare Program, NSW Government's Department of Planning, Industry and Environment. TERN enabled by the NCRIS National Research Infrastructure for Australia, and a Sydney Life Grant from the University of Sydney.
Glenda is Chair of the Ecosystem Science Council and a member of the University of Sydney's Charles Perkins Centre Citizen Science Node.</span></em></p><p class="fine-print"><em><span>Rebecca Cross receives funding from NSW Environmental Trust and the Australian Centre for International Agricultural Research (ACIAR).</span></em></p><p class="fine-print"><em><span>Rosanne Quinnell receives funding from The University of Sydney for a Student Life Grant and is member of the University of Sydney's Charles Perkins Centre Citizen Science Node.</span></em></p><p class="fine-print"><em><span>Samantha Rowbotham has receives funding from The Australian Prevention Partnership Centre, which is was funded by the National Health and Medical Research Council of Australia (NHMRC) through its Partnership Centre grant scheme. Samantha is a members of the Menzies Centre for Health Policy and the University of Sydney's Charles Perkins Centre Citizen Science Node.</span></em></p><p class="fine-print"><em><span>Yun-Hee Jeon receives funding from the National Health and Medical Research Council. Yun-Hee is a Lead for Charles Perkins Centre Citizen Science Node, The University of Sydney. </span></em></p>As scientists frantically try to find drugs to slow COVID-19’s spread, citizen science offers an opportunity for all of us to get involved.Ayesha Tulloch, DECRA Research Fellow, University of SydneyAaron Greenville, Lecturer in Spatial Agricultural and Environmental Sciences, University of SydneyAlice Motion, Associate professor, University of SydneyCobi Calyx, Research Fellow in Science Communication, UNSW SydneyGlenda Wardle, Professor of Ecology and Evolution, University of SydneyRebecca Cross, Lecturer in Human Geography, University of SydneyRosanne Quinnell, Associate Professor, University of SydneySamantha Rowbotham, Lecturer, Health Policy, University of SydneyYun-Hee Jeon, Susan and Isaac Wakil Professor of Healthy Ageing, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1330542020-03-17T19:46:25Z2020-03-17T19:46:25ZViruses live on doorknobs and phones and can get you sick – smart cleaning and good habits can help protect you<figure><img src="https://images.theconversation.com/files/320286/original/file-20200312-111300-zgdow6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Disinfecting an area takes time and effort. And there is only so much you can do. </span> <span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Virus-Outbreak-New-York/4af925c106ca40268d5db383657b355e/2/0">AP Photo/Seth Wenig</a></span></figcaption></figure><p>One vomiting episode from someone infected with norovirus <a href="https://dx.doi.org/10.3201/eid1410.080117">emits billions and billions of individual viruses</a>. That’s enough to fuel an outbreak – and is exactly what happened in an elementary school in <a href="https://www.usatoday.com/story/news/health/2019/12/13/norovirus-outbreak-stomach-flu-terrorizes-washington-public-schools/4417867002/">Seattle, Washington a few months ago</a>. Over 100 children got sick with the stomach-churning bug, and the school doors remained closed until workers could decontaminate the lockers, desks and hallways.</p>
<p>You might think of germs mostly passing directly from one person to another, but the outbreak in Seattle illustrates how they can survive on and be transmitted by inanimate objects in the world around us. <a href="https://sph.umich.edu/faculty-profiles/eisenberg-joseph.html">Epidemiologists like me</a> call these everyday objects – like doorknobs, elevator buttons and cellphones – fomites, and when contaminated, these fomites can make you sick. </p>
<p>Fomites can be an important pathway of disease transmission. They were the main culprits in that norovirus outbreak in Seattle last year and have been the cause of many other outbreaks. In 1908, <a href="https://dx.doi.org/10.1128%2FAEM.02051-06">smallpox outbreaks were traced to contaminated imported cotton</a>. More recently, <a href="https://doi.org/10.1093/oxfordjournals.aje.a113661">outbreak studies in day care centers</a> have identified viruses on <a href="https://www.ncbi.nlm.nih.gov/pubmed/8393172">toys, phones, toilet handles, sinks and water fountains</a>.</p>
<h2>The novel coronavirus</h2>
<p>The coronavirus is spreading quickly. As concern has increased, I’ve seen more people washing their hands and using hand sanitizer than ever before. While there is still a lot we don’t know about the new coronavirus, SARS-CoV-2, history would suggest that there is probably some transmission from fomites. Everyone should be washing their hands and using hand sanitzer, but taking efforts to clean the things around you is also important to fight the spread of the virus.</p>
<p>For instance, in the last major coronavirus pandemic, SARS in 2002, contaminated surfaces were a major contributor to over <a href="https://dx.doi.org/10.1258%2Fjrsm.96.8.374">300 cases in a Hong Kong apartment building</a>.</p>
<p>When thinking about how risky transmission via fomites is in an outbreak, the important question is how long can a particular bug survive on surfaces. And there is a lot of variation. Some pathogens can last outside the body for only minutes, while others are hardier and can hold on for days or even months. A new study suggests that the novel coronavirus <a href="https://doi.org/10.1101/2020.03.09.20033217">can survive on some surfaces up to three days</a>, but it varies depending on the material. The study found that the virus could survive for 24 hours on cardboard and up to three days on plastic and stainless steel.</p>
<p>This variation is caused in part by the <a href="https://doi.org/10.1186/1471-2334-6-130">properties of the surface a virus lands on</a>. Porous material like clothing may allow pathogens to survive longer but it can be harder for a virus to move <a href="https://doi.org/10.1128/AEM.01030-13">from your shirt to someone else’s fingers</a>. The matrix fibers in nonporous materials can trap germs making it hard for them to transfer. On the other hand, viruses can more readily transfer from nonporous materials like the glass screen on your phone to fingers, but the virus won’t always survive as long on a glass surface compared to a sweater.</p>
<p>Environmental conditions such as <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC201876/">temperature and humidity also influence the viability of a pathogen in the environment</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/320291/original/file-20200312-111268-3h808r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/320291/original/file-20200312-111268-3h808r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/320291/original/file-20200312-111268-3h808r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/320291/original/file-20200312-111268-3h808r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/320291/original/file-20200312-111268-3h808r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/320291/original/file-20200312-111268-3h808r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/320291/original/file-20200312-111268-3h808r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/320291/original/file-20200312-111268-3h808r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Most viruses will eventually die on their own. But cleaning with alcohol, bleach and other chemicals can kill them more quickly.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Ukraine-Virus-Outbreak/6b99329a97094a578d3b689b6f5d9924/20/0">AP Photo/Efrem Lukatsky</a></span>
</figcaption>
</figure>
<h2>Persistent bugs and how to get rid of them</h2>
<p>It’s nearly impossible to keep anything in the real world virus-free, but during outbreaks like this one it’s a good idea to try to minimize the number of viruses on fomites around you. Some people are practically bathing in hand sanitizer and wiping down everything they touch with disinfectant. But whether this works depends on what virus you are hoping to kill.</p>
<p>Norovirus, for example, is notoriously hardy. After an outbreak on a cruise ship in 2002, the next group of passengers got sick <a href="https://dx.doi.org/10.3201%2Feid1101.040434">more than a week later after a thorough cleaning of the ship</a>. Many standard cleaners like alcohol or Lysol do not kill norovirus. It takes something as strong as chlorine bleach to get the job done. </p>
<p>In contrast to norovirus, <a href="https://dx.doi.org/10.1128%2FAEM.02051-06">influenza is much less persistent in the environment</a>. While influenza is often lurking in daycare centers during flu season, it typically lasts on surfaces only for hours or a few days. And if you wanted to clean off your phone or countertop, simply wiping it down with an alcohol-based product or ammonia is effective.</p>
<p>While virologists don’t know much about how tough the current coronavirus is, past coronaviruses have fallen somewhere between norovirus and the flu. Like influenza, Lysol will likely kill the coronavirus.</p>
<p>But you don’t necessarily need to kill the virus to make yourself safer. Removing the virus can be just as effective and simply <a href="https://www.cdc.gov/handwashing/show-me-the-science-hand-sanitizer.html">washing often-used objects or your hands with soap can do that</a>.</p>
<p>If you have been in crowded areas or want to be extra careful, washing your hands with soap for 20 seconds will effectively remove germs, and disinfecting tabletops and gym equipment with ammonia will effectively kill most germs.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/320289/original/file-20200312-111237-38wj0i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/320289/original/file-20200312-111237-38wj0i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/320289/original/file-20200312-111237-38wj0i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/320289/original/file-20200312-111237-38wj0i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/320289/original/file-20200312-111237-38wj0i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/320289/original/file-20200312-111237-38wj0i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/320289/original/file-20200312-111237-38wj0i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/320289/original/file-20200312-111237-38wj0i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Viruses are on everything. How you behave around them matters.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/asian-woman-with-protective-face-mask-using-royalty-free-image/1203348066?adppopup=true">d3sign/Moment via Getty Images</a></span>
</figcaption>
</figure>
<h2>What can you do in a world with viruses everywhere?</h2>
<p>During the coronavirus pandemic, it is important to clean the objects you touch frequently, like keyboards, tabletops and gym equipment.</p>
<p>But while fomites are known to be the culprits in many outbreaks, an individual’s risk depends on a lot of factors. Someone who touches contaminated surfaces frequently, like a health care worker, <a href="https://www.nytimes.com/interactive/2020/03/15/business/economy/coronavirus-worker-risk.html">is more likely to get sick than someone who doesn’t</a>. Risk also depends on personal habits, such as how often one touches their eyes, nose and mouth. And for most infectious diseases, whether someone gets sick and the severity of the illness depends on age and underlying health conditions.</p>
<p>Cleaning objects frequently with a disinfectant is the best way to mitigate the risk of transmission from everyday objects. Hand-washing is also important, especially if done reliably right after coming home from a public place.</p>
<p>Given that germs are ubiquitous, it’s easy to become germ-phobic and strive for a sterile environment. But keep in mind that while basic precautions are important, germs will always find a way to exploit our human environment. You can and should minimize risk, but germs are here to stay. </p>
<p>[<em>You’re smart and curious about the world. So are The Conversation’s authors and editors.</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=youresmart">You can read us daily by subscribing to our newsletter</a>.]</p><img src="https://counter.theconversation.com/content/133054/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Joseph Eisenberg does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The coronavirus, like many infectious diseases, can live and spread on inanimate objects in the world around us. An epidemiologist explains how and gives some advice on how to minimize the risk.Joseph Eisenberg, Professor and Chair of Epidemiology, University of MichiganLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1307732020-02-06T13:44:11Z2020-02-06T13:44:11ZRe-creating live-animal markets in the lab lets researchers see how pathogens like coronavirus jump species<figure><img src="https://images.theconversation.com/files/313831/original/file-20200205-149796-b6cnv8.jpg?ixlib=rb-1.1.0&rect=0%2C298%2C3521%2C2432&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Places where lots of animals come into contact can help pathogens move from species to species.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/chickens-in-cages-royalty-free-image/1001442114">Baloncici/iStock via Getty Images Plus</a></span></figcaption></figure><p>Nobody yet knows for sure the definitive origins of the <a href="https://theconversation.com/us/topics/wuhan-coronavirus-81516">newly recognized coronavirus</a> now known as 2019-nCoV that’s currently spreading across the globe as a human respiratory pathogen. Early reports indicate that the <a href="https://doi.org/10.3390/v12020135">source of the virus was the Huanan seafood market in Wuhan, China</a>, where an eclectic mix of animals including rodents, rabbits, bats and other wild animals and seafood are all on display for consumption and in contact with human shoppers.</p>
<p>Over the past two decades, the world has seen the <a href="https://doi.org/10.1038/nature06536">emergence of multiple pandemic threats</a>, including bird flu (H5N1 avian influenza), SARS, Ebola, Middle East Respiratory Syndrome, chikungunya, Zika and now the new coronavirus from Wuhan. The viruses that cause these diseases, and indeed <a href="https://www.cdc.gov/onehealth/basics/zoonotic-diseases.html">roughly two-thirds of all recent emergent viruses</a>, originate in animals before they jump to humans. </p>
<p>Each of these events underscores that multiple parts of an ecosystem are at play during an outbreak. For instance, <a href="https://doi.org/10.1098/rspb.2012.2753">wild bats and rodents harbor numerous viruses</a> that have the potential to infect humans and animals. When these wild animals are extracted from their natural habitat and come into close contact with people, very rare transmission events become much more likely.</p>
<p>These pathogen jumps are complex. They can occur via direct contact, consumption of bushmeat or transmission by insect vectors that carry the germs among a variety of species. And a range of environmental conditions – such as temperature, humidity, sunlight and even seasonal rain and soil conditions – can affect transmission. </p>
<p>Despite the complexity of the natural world, the research approach to understanding how potentially pandemic pathogens and their animal and human hosts interact has been relatively simple. Scientists typically focus on a single species at a time, studied under conditions of constant temperature, humidity and airflow. This strategy has clearly helped researchers understand infectious disease processes.</p>
<p>But <a href="https://scholar.google.com/citations?user=aDassZsAAAAJ&hl=en&oi=ao">as biologists</a>, <a href="https://www.research.colostate.edu/executive-committee/alan-rudolph/">we believe</a> that more explicitly acknowledging the complexity of the natural world will provide a more robust understanding of emerging infectious diseases. We’ve set up what we call “artificial ecosystems” in the lab to mimic the complicated conditions out in the real world. They’re helping us gather new insights into how viruses and other pathogens actually emerge to become global threats.</p>
<h2>Reconstructing live-animal markets and barnyards</h2>
<p>It’s undoubtedly rare for pathogens to jump directly from animals in nature into people. But within markets like the one in Wuhan, there are abundant opportunities for the type of interactions that promote pathogen transmission among species.</p>
<p>To mimic these scenarios, we’ve established artificial ecosystems in our lab. That way, we can study the transmission and spread of pathogens, such as influenza viruses, among diverse groups of birds and mammals all housed together and interacting freely.</p>
<p>Because the pathogens we’re studying are potentially deadly and contagious, we need to be very careful they can’t escape from the lab. We establish our ecosystems under strict biocontainment conditions: All exhaust air is filtered and personnel use respirators, wear facility apparel and shower before exiting.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/313396/original/file-20200203-41490-1ndvdft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/313396/original/file-20200203-41490-1ndvdft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/313396/original/file-20200203-41490-1ndvdft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=369&fit=crop&dpr=1 600w, https://images.theconversation.com/files/313396/original/file-20200203-41490-1ndvdft.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=369&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/313396/original/file-20200203-41490-1ndvdft.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=369&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/313396/original/file-20200203-41490-1ndvdft.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=464&fit=crop&dpr=1 754w, https://images.theconversation.com/files/313396/original/file-20200203-41490-1ndvdft.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=464&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/313396/original/file-20200203-41490-1ndvdft.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=464&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A live-animal market in Indonesia (left) and an artificial market established to study interspecies transmission of avian influenza viruses as viewed through the window of a biosafety containment level 3 room.</span>
<span class="attribution"><span class="source">Richard Bowen</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>For our studies with bird flu, we created artificial barnyards that housed ducks, chickens, pigeons, blackbirds and rats all together. They freely interacted with one another, sharing access to common feed and water. As occurs in real barnyards, the rats were never seen outside of their enclosed nests during daylight hours, though video recordings showed them cavorting around the room, bathing in the water pool and harassing the ducks in the dark. We then <a href="https://doi.org/10.1371/journal.pone.0017643">introduced a small number of infected ducks</a> into the room and watched to see how infection spread. </p>
<p>In a different setup, we investigated transmission of another avian influenza virus among chickens, quail, pheasants and rabbits caged as in a live-animal market. Additionally, sparrows and pigeons were loose in the room and able to interact with the caged animals. As anticipated, <a href="https://doi.org/10.1016/j.virol.2016.04.032">birds housed beneath those inoculated with virus</a> were more likely be become infected, as waste runs downhill. Quail were the most susceptible to infection.</p>
<p>Key discoveries have emerged from our artificial ecosystem approach. For example, we were able to show that avian influenza viruses pass among diverse birds and mammals interacting freely with one another in an artificial barnyard or artificial live-animal market. We found that there’s <a href="https://doi.org/10.1371/journal.pone.0017643">massive accumulation of virus in shared water sources</a>.</p>
<p>More recently, we’ve created even more sophisticated artificial ecosystems that allow us to modulate temperature and humidity. We can even impose rain and wind onto an ecosystem, allowing us to evaluate environmental conditions that facilitate virus transmission.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/313833/original/file-20200205-149772-88nj5l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/313833/original/file-20200205-149772-88nj5l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/313833/original/file-20200205-149772-88nj5l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/313833/original/file-20200205-149772-88nj5l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/313833/original/file-20200205-149772-88nj5l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/313833/original/file-20200205-149772-88nj5l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/313833/original/file-20200205-149772-88nj5l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/313833/original/file-20200205-149772-88nj5l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Artificial ecosystems complement other research approaches that identify viruses and their properties.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/coronavirus-virus-royalty-free-image/1203566633">xia yuan/Moment via Getty Images</a></span>
</figcaption>
</figure>
<h2>Lessons from inside the artificial ecosystems</h2>
<p>Despite the known complexity of these sorts of interactions in the real world, it’s more typical to study emerging pathogens by focusing on infection in a single species at a time. This is partly due to the <a href="https://www.fda.gov/drugs/drug-development-tool-ddt-qualification-programs/animal-model-qualification-amqp-program">regulatory processes</a> by which diagnostics or vaccines are approved. They require definitive demonstration of safety and efficacy in individual animal models.</p>
<p>We hope this new approach could foster a more realistic understanding of how pathogens are transmitted among species, including jumping into human populations, and will facilitate development of new diagnostic tests, vaccines or therapeutics.</p>
<p>Our ecosystem method fits in with what’s called the <a href="https://www.cdc.gov/onehealth/index.html">One Health</a> approach to public health. One Health is based on the concept that human health is inextricably tied to the health of animals and the environment. Understanding infection in natural hosts in mixed ecosystems that mimic real-world scenarios of transmission is crucial for developing disease control methods.</p>
<p>[<em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>.]</p><img src="https://counter.theconversation.com/content/130773/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Richard Bowen receives funding from NIH, CDC, DTRA.</span></em></p><p class="fine-print"><em><span>Alan Rudolph is a member of the board of the Colorado Biosciences Association.</span></em></p>In the real world, new diseases emerge from complex environments. To learn more about how, scientists set up whole artificial ecosystems in the lab, instead of focusing on just one factor at a time.Richard Bowen, Professor of Biomedical Sciences, Colorado State UniversityAlan Rudolph, Professor of Biomedical Sciences and Vice President for Research, Colorado State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1307772020-02-05T12:55:16Z2020-02-05T12:55:16ZR0: How scientists quantify the intensity of an outbreak like coronavirus and predict the pandemic’s spread<figure><img src="https://images.theconversation.com/files/313588/original/file-20200204-41516-vr3j0h.jpg?ixlib=rb-1.1.0&rect=622%2C142%2C7441%2C5341&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">To how many others will one infected person spread the infection?</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/large-group-of-people-royalty-free-image/937887974">Bim/E+ via Getty Images</a></span></figcaption></figure><p><em>Leer en <a href="https://theconversation.com/que-es-el-r0-el-numero-que-siguen-los-cientificos-para-ver-la-intensidad-del-coronavirus-137744">español</a></em></p>
<p>If you saw the 2011 movie “<a href="https://www.imdb.com/title/tt1598778/">Contagion</a>,” about a worldwide pandemic of a new virus, then you’ve heard the term “R0.” </p>
<p>Pronounced “R naught,” this isn’t just jargon made up in Hollywood. It represents an important concept in epidemiology and is a crucial part of public health planning during an outbreak, like the current coronavirus pandemic that’s spread globally since it was first identified in China.</p>
<p>Scientists use R0 – <a href="https://doi.org/10.3201/eid2501.171901">the reproduction number</a> – to describe the intensity of an infectious disease outbreak. R0 estimates have been an important part of characterizing pandemics or large publicized outbreaks, including the <a href="https://www.jstor.org/stable/20486145">2003 SARS pandemic</a>, the <a href="https://doi.org/10.1186/1471-2334-14-480">2009 H1N1 influenza pandemic</a> and the <a href="https://doi.org/10.1371/currents.outbreaks.91afb5e0f279e7f29e7056095255b288">2014 Ebola epidemic in West Africa</a>. It’s something epidemiologists are racing to nail down about SARS-CoV-2, the virus that causes COVID-19.</p>
<h2>How much will a disease spread?</h2>
<p>The formal definition of a disease’s R0 is the number of cases, on average, an infected person will cause during their infectious period. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/312353/original/file-20200128-120039-bogv2t.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/312353/original/file-20200128-120039-bogv2t.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=621&fit=crop&dpr=1 600w, https://images.theconversation.com/files/312353/original/file-20200128-120039-bogv2t.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=621&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/312353/original/file-20200128-120039-bogv2t.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=621&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/312353/original/file-20200128-120039-bogv2t.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=780&fit=crop&dpr=1 754w, https://images.theconversation.com/files/312353/original/file-20200128-120039-bogv2t.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=780&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/312353/original/file-20200128-120039-bogv2t.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=780&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">R0 describes how many cases of a disease an infected person will go on to cause – in this imagined scenario R0=2.</span>
<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The term is used in two different ways. </p>
<p>The basic reproduction number represents the maximum epidemic potential of a pathogen. It describes what would happen if an infectious person were to enter a fully susceptible community, and therefore is an estimate based on an idealized scenario.</p>
<p>The effective reproduction number depends on the population’s current susceptibility. This measure of transmission potential is likely lower than the basic reproduction number, based on factors like whether some of the people are vaccinated against the disease, or whether some people have immunity due to prior exposure with the pathogen. Therefore, the effective R0 changes over time and is an estimate based on a more realistic situation within the population.</p>
<p>It’s important to realize that both the <a href="https://dx.doi.org/10.3201/eid2501.171901">basic and effective R0 are situation-dependent</a>. It’s affected by the properties of the pathogen, such as how infectious it is. It’s affected by the host population – for instance, how susceptible people are due to nutritional status or other illnesses that may compromise one’s immune system. And it’s affected by the environment, including things like demographics, socioeconomic and climatic factors.</p>
<p>For example, <a href="https://doi.org/10.1016/S1473-3099(17)30307-9">R0 for measles ranges from 12 to 18</a>, depending on factors like population density and life expectancy. This is a large R0, mainly because the measles virus is highly infectious.</p>
<p>On the other hand, the influenza virus is less infectious, with <a href="https://doi.org/10.1186/1471-2334-14-480">its R0 ranging</a> <a href="https://doi.org/10.1017/S0950268807009144">from 0.9 to 2.1</a>. Influenza, therefore, does not cause the same explosive outbreaks as measles, but it persists due to its ability to mutate and evade the human immune system. </p>
<h2>What makes R0 useful in public health?</h2>
<p>Demographer Alfred Lotka proposed the reproduction number in the 1920s, as a measure of the rate of reproduction in a given population.</p>
<p>In the 1950s, <a href="https://doi.org/10.1371/journal.ppat.1002588">epidemiologist George MacDonald suggested</a> using it to describe the transmission potential of malaria. He proposed that, if R0 is less than 1, the disease will die out in a population, because on average an infectious person will transmit to fewer than one other susceptible person. On the other hand, if R0 is greater than 1, the disease will spread.</p>
<p><iframe id="BOmTu" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/BOmTu/7/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>When public health agencies are figuring out how to deal with an outbreak, they are trying to bring R0 down to less than 1. This is tough for diseases like measles that have a high R0. It is <a href="https://www.cdc.gov/mmwr/PDF/rr/rr4711.pdf">especially challenging for measles in densely populated regions</a> like India and China, where R0 is higher, compared to places where people are more spread out.</p>
<p>For the <a href="https://doi.org/10.1126/science.1086478">SARS pandemic in 2003</a>, scientists estimated the original R0 to be around 2.75. A month or two later, the effective R0 dropped below 1, thanks to the tremendous effort that went into intervention strategies, including isolation and quarantine activities.</p>
<p>However, the pandemic continued. While on average, an infectious person transmitted to fewer than one susceptible individual, occasionally one person transmitted to tens or even hundreds of other cases. This phenomenon <a href="https://theconversation.com/what-is-a-super-spreader-an-infectious-disease-expert-explains-130756">is called super spreading</a>. Officials documented super spreader events a number of times during the SARS epidemic in Singapore, Hong Kong and Beijing.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/313590/original/file-20200204-41495-8uhzhq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/313590/original/file-20200204-41495-8uhzhq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/313590/original/file-20200204-41495-8uhzhq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=408&fit=crop&dpr=1 600w, https://images.theconversation.com/files/313590/original/file-20200204-41495-8uhzhq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=408&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/313590/original/file-20200204-41495-8uhzhq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=408&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/313590/original/file-20200204-41495-8uhzhq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=512&fit=crop&dpr=1 754w, https://images.theconversation.com/files/313590/original/file-20200204-41495-8uhzhq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=512&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/313590/original/file-20200204-41495-8uhzhq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=512&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">People in Hong Kong, concerned about coronavirus spreading from mainland China, wear face masks in February 2020.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Hong-Kong-China-Outbreak/3e0e13e1d7c44ce3a8439c982e27c797/1/0">AP Photo/Vincent Yu</a></span>
</figcaption>
</figure>
<h2>R0 for coronavirus SARS-CoV-2</h2>
<p>A number of groups have estimated R0 for this new coronavirus. The Imperial College group has estimated R0 to be <a href="https://www.imperial.ac.uk/mrc-global-infectious-disease-analysis/news--wuhan-coronavirus/">somewhere between 1.5 and 3.5</a>. Most modeling simulations that project future cases are using R0s in that range.</p>
<p>These differences are not surprising; there’s uncertainty about many of the factors that go into estimating R0, such as in estimating the number of cases, especially early on in an outbreak. </p>
<p>Based on these current estimates, projections of the future number of cases of coronavirus are fraught with high levels of uncertainty and will likely be somewhat inaccurate.</p>
<p>The difficulties arise for a number of reasons. </p>
<p>First, the basic properties of this viral pathogen – like the infectious period – are as yet unknown.</p>
<p>Second, researchers don’t know how many mild cases or infections that don’t result in symptoms have been missed by surveillance but nevertheless are spreading the disease.</p>
<p>Third, the majority of people who come down with this new coronavirus do recover, and are likely then immune to coming down with it again. It’s unclear how the changing susceptibility of the population will affect the future spread of infection. As the virus moves into new regions and communities, it encounters people with varying health conditions that affect their susceptibility to disease, as well as different social structures, both of which affect its transmissibility. </p>
<p>Finally, and likely the most important reason, no one knows the future impacts of current disease control measures. Epidemiologists’ current estimates of R0 say nothing about how measures such as <a href="https://www.washingtonpost.com/local/trafficandcommuting/white-house-considers-moving-all-of-europe-to-level-3-travel-advisory/2020/03/11/844090d0-63bc-11ea-b3fc-7841686c5c57_story.html">travel restrictions</a>, <a href="https://www.cdc.gov/coronavirus/2019-ncov/php/risk-assessment.html">social distancing</a> and <a href="https://theconversation.com/coronavirus-control-measures-arent-pointless-just-slowing-down-the-pandemic-could-save-millions-of-lives-133468">self-quarantine efforts</a> will influence the virus’s continued spread.</p>
<hr>
<p><em>This is an updated version of an article originally published on Feb. 5, 2020. The reproduction number for seasonal flu was corrected on March 27, 2020.</em></p><img src="https://counter.theconversation.com/content/130777/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Joseph Eisenberg does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Epidemiologists want to quickly identify any emerging disease’s potential to spread far and wide. Dependent on a number of factors, this R0 number helps them figure that out and plan accordingly.Joseph Eisenberg, Professor and Chair of Epidemiology, University of MichiganLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1306802020-02-03T13:52:09Z2020-02-03T13:52:09ZQuarantines have tried to keep out disease for thousands of years<figure><img src="https://images.theconversation.com/files/313148/original/file-20200131-41532-1dh028v.jpg?ixlib=rb-1.1.0&rect=325%2C149%2C5323%2C3378&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Camp beds set up for travelers returning to Germany from China, who will be isolated for two weeks to make sure they don't have coronavirus. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/picture-taken-on-january-31-shows-camp-beds-seen-behind-news-photo/1197696121?adppopup=true">YANN SCHREIBER/AFP via Getty Images</a></span></figcaption></figure><p>The recent global spread of a <a href="https://theconversation.com/us/topics/wuhan-coronavirus-81516">deadly coronavirus originating in Wuhan, China</a>, has led world leaders to invoke an ancient tradition to control the spread of illness: quarantine.</p>
<p>The practice is first recorded in the Old Testament where <a href="https://www.biblegateway.com/passage/?search=Numbers+5%3A2-3&version=NIV">several verses</a> <a href="https://www.biblegateway.com/passage/?search=Leviticus+13%3A46&version=NIV">mandate isolation</a> for those <a href="https://www.biblegateway.com/passage/?search=2+Kings+15%3A5&version=NIV">with leprosy</a>. Ancient civilizations relied on isolating the sick, well before the actual microbial causes of disease were known. In times when treatments for illnesses were rare and public health measures few, physicians and lay leaders, beginning <a href="https://doi.org/10.1111/j.1748-720X.2007.00185.x">as early as the ancient Greeks</a>, turned to quarantine to contain a scourge.</p>
<p>In January, Chinese authorities attempted to <a href="https://www.theatlantic.com/health/archive/2020/01/china-quarantine-coronavirus/605455/">lock down millions of residents of Wuhan</a> and the surrounding area, to try to keep the new coronavirus from spreading outward. The country’s neighbors are <a href="https://www.newsweek.com/china-neighbors-close-borders-coronavirus-sars-1484978">closing borders</a>, airlines are <a href="https://www.digitaltrends.com/news/united-delta-and-american-airlines-suspend-flights-to-china-over-coronavirus/">canceling flights</a>, and nations are advising their citizens <a href="https://travel.state.gov/content/travel/en/traveladvisories/traveladvisories/china-travel-advisory.html">against traveling to China</a>, a modern instance of the old impulse to restrict people’s movements in order to stop disease transmission.</p>
<p>U.S. authorities are <a href="https://www.washingtonpost.com/world/coronavirus-china-live-updates/2020/01/31/eeac61b6-442b-11ea-b503-2b077c436617_story.html">holding travelers returning from China</a> in isolation for two weeks as an effort to halt coronavirus’ spread. Always at the center of the policy of quarantine is the tension between individual civil liberties and protection of the public at risk.</p>
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<h2>Keeping contagion at bay</h2>
<p>The meaning of quarantine has evolved from its <a href="https://doi.org/10.1016/j.jinf.2004.03.002">original definition</a> “as the detention and segregation of subjects suspected to carry a contagious disease.”</p>
<p>Now it represents a period of isolation for persons or animals with a contagious disease – or who may have been exposed but aren’t yet sick. Although in the past it may have been a self-imposed or voluntary separation from society, in more recent times quarantine has come to represent a compulsory action enforced by health authorities.</p>
<p>Leprosy, mentioned in both Old and New testaments, is the first documented disease for which quarantine was imposed. In the Middle Ages, leper colonies, administered by the Catholic Church, sprung up throughout the world. Although the causative agent of leprosy – the bacterium <em>Mycobacterium leprae</em> – was <a href="https://www.archivesofpathology.org/doi/full/10.1043/0003-9985(2000)124%3C0496%3ATLOAH%3E2.0.CO%3B2">not discovered until 1873</a>, its disfiguring and incurable nature made civilizations wrongly believe it was easily spread.</p>
<p>The <a href="https://doi.org/10.1016/j.jinf.2004.03.002">plague of the 14th century</a> gave rise to the modern concept of quarantine. The Black Death first appeared in Europe in 1347. Over the course of four years, it would kill between 40 million and 50 million people in Europe and somewhere between 75 million and 200 million worldwide.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/313147/original/file-20200131-41527-1gm2hxk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/313147/original/file-20200131-41527-1gm2hxk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/313147/original/file-20200131-41527-1gm2hxk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=296&fit=crop&dpr=1 600w, https://images.theconversation.com/files/313147/original/file-20200131-41527-1gm2hxk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=296&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/313147/original/file-20200131-41527-1gm2hxk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=296&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/313147/original/file-20200131-41527-1gm2hxk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=372&fit=crop&dpr=1 754w, https://images.theconversation.com/files/313147/original/file-20200131-41527-1gm2hxk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=372&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/313147/original/file-20200131-41527-1gm2hxk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=372&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Now part of Croatia, Ragusa was in the Venetian Republic when it invented the 40-day quarantine to try to keep the plague out.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/aerial-view-sunset-scene-of-dubrovnik-old-town-royalty-free-image/1186203393?adppopup=true">Ratnakorn Piyasirisorost/Getty Images</a></span>
</figcaption>
</figure>
<p>In 1377, the seaport in Ragusa, modern day Dubrovnik, issued a “trentina” – derived from the Italian word for 30 (trenta). Ships traveling from areas with high rates of plague were required to stay offshore for 30 days before docking. Anyone onboard who was healthy at the end of the waiting period was presumed unlikely to spread the infection and allowed onshore.</p>
<p>Thirty was eventually extended to 40 days, giving rise to the term quarantine, from the Italian word for 40 (quaranta). It was in Ragusa that the first law to enforce the act of quarantine was implemented. </p>
<p>Over time, variations in the nature and regulation of quarantine emerged. Port officials asked travelers to certify they hadn’t been to areas with severe disease outbreaks, before allowing them to enter. In the 19th century, <a href="https://doi.org/10.1001/jama.290.21.2873">quarantine was abused</a> for political and economic reasons, leading to the call for international conferences to standardize quarantine practices. Cholera epidemics throughout the early 19th century made clear the <a href="https://doi.org/10.3201/eid1902.120312">lack of any uniformity of policy</a>.</p>
<h2>Imported to America</h2>
<p>The United States has also had its share of epidemics, beginning in 1793, with the <a href="https://www.pabook.libraries.psu.edu/literary-cultural-heritage-map-pa/feature-articles/philadelphia-under-siege-yellow-fever-1793">outbreak of yellow fever</a> in Philadelphia. A series of further disease outbreaks led Congress in 1878 to pass laws that mandated involvement of the federal government in quarantine. The arrival of cholera to the United States, in 1892, prompted <a href="https://doi.org/10.2307/2140865">even greater regulation</a>.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/312638/original/file-20200129-92964-kxqly8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/312638/original/file-20200129-92964-kxqly8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/312638/original/file-20200129-92964-kxqly8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=636&fit=crop&dpr=1 600w, https://images.theconversation.com/files/312638/original/file-20200129-92964-kxqly8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=636&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/312638/original/file-20200129-92964-kxqly8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=636&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/312638/original/file-20200129-92964-kxqly8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=800&fit=crop&dpr=1 754w, https://images.theconversation.com/files/312638/original/file-20200129-92964-kxqly8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=800&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/312638/original/file-20200129-92964-kxqly8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=800&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Officials quarantined ‘Typhoid’ Mary Mallon in a hospital.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Mary_Mallon_in_hospital.jpg">Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>Perhaps the best known example of quarantine in American history, pitting an individual’s civil liberties against public protection, is <a href="https://doi.org/10.1080/00219266.1998.9655608">the story of Mary Mallon</a>, aka “Typhoid Mary.” An asymptomatic carrier of typhoid fever in the early 20th century, she never felt sick but nevertheless spread the disease to families for whom she worked as a cook.</p>
<p>Officials quarantined Mary on North Brother Island in New York City. Released after three years, she promised never to cook for anyone again. Breaking her vow and continuing to spread the disease, she was returned to North Brother Island, where she remained for the remainder of her life in isolation.</p>
<p>More recently, in 2007, public health officials quarantined <a href="https://www.nytimes.com/2007/07/27/health/27tb.html">a 31-year-old Atlanta attorney, Andrew Speaker</a>, who was infected with a drug-resistant form of tuberculosis. His case grabbed international attention when he traveled to Europe, despite knowing he had and could spread this form of TB. Fearing quarantine in Italy, he returned to the United States, where he was apprehended by federal authorities and quarantined at a medical center in Denver, where he also received treatment. Following release, deemed no longer contagious, he was required to report to local health officials five days a week through the end of his treatment.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/313149/original/file-20200131-41495-1j7urbf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/313149/original/file-20200131-41495-1j7urbf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/313149/original/file-20200131-41495-1j7urbf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=683&fit=crop&dpr=1 600w, https://images.theconversation.com/files/313149/original/file-20200131-41495-1j7urbf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=683&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/313149/original/file-20200131-41495-1j7urbf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=683&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/313149/original/file-20200131-41495-1j7urbf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=859&fit=crop&dpr=1 754w, https://images.theconversation.com/files/313149/original/file-20200131-41495-1j7urbf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=859&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/313149/original/file-20200131-41495-1j7urbf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=859&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Quarantine stations in the U.S. are staffed with quarantine medical and public health officers from the CDC.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Quarantine-Officer/8edb404d72a54da8b384e1215279d4a1/1/0">AP Photo/Charles Rex Arbogast</a></span>
</figcaption>
</figure>
<p>Quarantine today continues as a public health measure to limit the spread of contagious disease, including not just coronavirus, but <a href="https://www.cdc.gov/quarantine/aboutlawsregulationsquarantineisolation.html">Ebola, flu and SARS</a>.</p>
<p>Its stigma has largely been removed by emphasizing not only the benefits of quarantine to society, by removing contagious individuals from the general population, but also the benefit of treatment to those who are ill.</p>
<p>In the United States, where the Constitution guarantees personal rights, it’s a serious decision to restrict an individual’s freedom of travel and compel medical treatment. And <a href="https://www.wired.com/story/would-the-coronavirus-quarantine-of-wuhan-even-work/">quarantine is not an ironclad way</a> to prevent the spread of disease. But it can be a useful tool for public health officials working to stop the spread of a contagious disease.</p>
<p>[ <em><a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=expertise">Expertise in your inbox. Sign up for The Conversation’s newsletter and get a digest of academic takes on today’s news, every day.</a></em> ]</p><img src="https://counter.theconversation.com/content/130680/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Leslie S. Leighton does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Even before people understood how germs spread disease, they tried to isolate the sick to keep them from infecting others.Leslie S. Leighton, Visiting Lecturer of History, Georgia State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1307562020-01-30T13:15:35Z2020-01-30T13:15:35ZWhat is a super spreader? An infectious disease expert explains<figure><img src="https://images.theconversation.com/files/312661/original/file-20200129-93030-9r9te1.jpg?ixlib=rb-1.1.0&rect=791%2C782%2C4490%2C3036&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Whether by biology or behavior, some people in the crowd will transmit coronavirus to more than the average number of others.</span> <span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Rattled-Markets-Virus/e258d7ca926d4ef7adc344a6d473193b/2/0">AP Photo/Kin Cheung</a></span></figcaption></figure><p><em>Editor’s Note: An updated version of this article was published on June 5, 2020. <a href="https://theconversation.com/a-few-superspreaders-transmit-the-majority-of-coronavirus-cases-139950">Read it here</a>.</em></p>
<hr>
<p><em>As the <a href="https://www.linkedin.com/pulse/dr-tom-frieden-former-cdc-director-latest-scientific-novel-frieden/">emerging Wuhan</a> <a href="https://theconversation.com/us/topics/coronavirus-5830">coronavirus outbreak</a> dominates the daily news, you might be wondering just how the pathogen is working its way around the world. This virus travels from place to place by infecting one person at a time. Some sick people might not spread the virus much further, but it looks like some people infected with the novel coronavirus are what epidemiologists call “super spreaders.”</em> </p>
<p><em><a href="https://scholar.google.com/citations?user=k4UBB88AAAAJ&hl=en&oi=ao">Elizabeth McGraw</a>, the director of the <a href="https://www.huck.psu.edu/institutes-and-centers/center-for-infectious-disease-dynamics">Center for Infectious Disease Dynamics</a> at Pennsylvania State University, explains just what that means and why super spreaders can be crucial to a disease’s transmission.</em></p>
<h2>What is a super spreader?</h2>
<p>Researchers currently estimate that a person carrying the Wuhan coronavirus
will, on average, <a href="https://www.imperial.ac.uk/mrc-global-infectious-disease-analysis/news--wuhan-coronavirus/">infect approximately 2.6 people</a>.</p>
<p>Recent reports out of Wuhan also cite a case of a single patient who <a href="https://www.cnn.com/2020/01/23/health/wuhan-virus-super-spreader/index.html">infected 14 health care workers</a>. That qualifies him as a super spreader: someone who is responsible for infecting an especially large number of other people.</p>
<p>During an emerging outbreak, epidemiologists want to determine whether super spreaders are part of the picture. Their existence can accelerate the rate of new infections or substantially expand the geographic distribution of the disease.</p>
<p>In response to super spreaders, officials can recommend various ways to limit their impact and slow the spread of disease, depending on how the pathogen is transmitted. Pathogens transmitted via air droplets, contaminated surfaces, sexual contact, needles, food or drinking water will require different interventions. For example, the recommendation for face masks would be specific to airborne transmission, while hand-washing and surface sterilization are needed for germs that can live for a while on surfaces.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/312664/original/file-20200129-92959-m1ltr9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/312664/original/file-20200129-92959-m1ltr9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/312664/original/file-20200129-92959-m1ltr9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/312664/original/file-20200129-92959-m1ltr9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/312664/original/file-20200129-92959-m1ltr9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/312664/original/file-20200129-92959-m1ltr9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/312664/original/file-20200129-92959-m1ltr9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/312664/original/file-20200129-92959-m1ltr9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A connected world of international travelers sets the stage for geographic super spreading.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/contrail-dark-blue-sky-beautiful-show-9683023">aleksander hunta/Shutterstock.com</a></span>
</figcaption>
</figure>
<h2>What are the characteristics of a super spreader?</h2>
<p>Whether someone is a super spreader or not will depend on some combination of the pathogen and the patient’s biology and their environment or behavior at the given time. And in a society with so much global connectivity, the ability to move pathogens rapidly across great distances, often before people are even aware they are sick, helps create environments ripe for super spreading. </p>
<p>Some infected individuals might shed more virus into the environment than others because of how their immune system works. Highly tolerant people do not feel sick and so may continue about their daily routines, inadvertently infecting more people. Alternatively, people with weaker immune systems that allow very high amounts of virus replication may be very good at transmitting even if they reduce their contacts with others. Individuals who have more symptoms – for example, coughing or sneezing more – can also be better at spreading the virus to new human hosts.</p>
<p>A person’s behaviors, travel patterns and degree of contact with others can also contribute to super spreading. An infected shopkeeper might come in contact with a large number of people and goods each day. An international business traveler may crisscross the globe in a short period of time. A sick health care worker might come in contact with large numbers of people who are especially susceptible, given the presence of other underlying illnesses.</p>
<h2>When have super spreaders played a key role in an outbreak?</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/312638/original/file-20200129-92964-kxqly8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/312638/original/file-20200129-92964-kxqly8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/312638/original/file-20200129-92964-kxqly8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=636&fit=crop&dpr=1 600w, https://images.theconversation.com/files/312638/original/file-20200129-92964-kxqly8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=636&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/312638/original/file-20200129-92964-kxqly8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=636&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/312638/original/file-20200129-92964-kxqly8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=800&fit=crop&dpr=1 754w, https://images.theconversation.com/files/312638/original/file-20200129-92964-kxqly8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=800&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/312638/original/file-20200129-92964-kxqly8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=800&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Officials quarantined ‘Typhoid’ Mary Mallon in a hospital.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Mary_Mallon_in_hospital.jpg">Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>There are a number of historical examples of super spreaders. The most famous is <a href="https://www.history.com/news/10-things-you-may-not-know-about-typhoid-mary">Typhoid Mary</a>, who in the early 20th century purportedly infected 51 people with typhoid through the food she prepared as a cook. Since Mary was an asymptomatic carrier of the bacteria, she didn’t feel sick, and so was not motivated to use good hand-washing practices.</p>
<p>During the last two decades, super spreaders have started a number of measles outbreaks in the United States. Sick, unvaccinated individuals visited densely crowded places like schools, hospitals, airplanes and theme parks where they <a href="https://doi.org/10.1001/jamapediatrics.2019.4357">infected many others</a>.</p>
<p>Super spreaders have also played a key role in the outbreaks of other coronaviruses, including SARS (severe acute respiratory syndrome) and MERS (Middle East respiratory syndrome). <a href="http://www.taipeitimes.com/News/world/archives/2004/02/23/2003099824/1">A traveler sick with SARS and staying in a Hong Kong hotel</a> infected a number of overseas guests who then returned home and introduced the virus into four other countries. </p>
<p>For both SARS and MERS, super spreading <a href="https://doi.org/10.1186/s12916-015-0450-0">commonly occurred in hospitals</a>, with scores of people being infected at a time. In South Korea in 2015, one MERS patient infected over 80 other patients, medical personnel and visitors in a crowded emergency department over a three-day period. In this case, <a href="http://www.cidrap.umn.edu/news-perspective/2016/07/patient-proximity-key-korean-mers-super-spreader-event">proximity to the original patient</a> was the biggest risk factor for getting sick.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/312662/original/file-20200129-92959-4qx7wt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/312662/original/file-20200129-92959-4qx7wt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/312662/original/file-20200129-92959-4qx7wt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/312662/original/file-20200129-92959-4qx7wt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/312662/original/file-20200129-92959-4qx7wt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/312662/original/file-20200129-92959-4qx7wt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/312662/original/file-20200129-92959-4qx7wt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/312662/original/file-20200129-92959-4qx7wt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Public health officials work to get the word out on how to protect yourself during an outbreak.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/South-Korea-China-Outbreak/9250d36b1f274996a9eb600a4af27dc7/1/0">AP Photo/Ahn Young-joon</a></span>
</figcaption>
</figure>
<h2>Can super spreading occur in all infectious diseases?</h2>
<p>Yes. Some scientists estimate that in any given outbreak, 20% of the population is usually responsible for <a href="https://doi.org/10.1038/438293a">causing over 80% of all cases of the disease</a>. Researchers have identified super spreaders in outbreaks of diseases from those caused by bacteria, such as tuberculosis, as well as those caused by viruses, including measles, <a href="https://doi.org/10.3947/ic.2016.48.2.147">MERS</a> and <a href="https://www.eurekalert.org/pub_releases/2017-02/osu-dw021017.php">Ebola</a>.</p>
<p>The good news is that <a href="https://www.cdc.gov/foodsafety/outbreaks/investigating-outbreaks/investigations/control.html">with the right</a> <a href="https://www.who.int/csr/disease/ebola/training/infection-prevention/en/">control practices</a> <a href="https://www.who.int/csr/bioriskreduction/infection_control/publication/en/">specific to how</a> <a href="https://www.who.int/ith/2020-24-01-outbreak-of-Pneumonia-caused-by-new-coronavirus/en/">pathogens are transmitted</a> – hand-washing, masks, quarantine, vaccination and so on – the transmission rate can be slowed and epidemics halted.</p>
<p><em>This article has been updated to correct a typo concerning the disease Typhoid Mary spread.</em></p><img src="https://counter.theconversation.com/content/130756/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Elizabeth McGraw receives funding from the National Institute of Allergy and Infectious Diseases. </span></em></p>The novel coronavirus spreading outward from Wuhan, China, will get an assist from a subset of infected people who transmit it to many others.Elizabeth McGraw, Professor of Entomology and Director of the Center for Infectious Disease Dynamics, Penn StateLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1303642020-01-22T20:03:23Z2020-01-22T20:03:23ZSnakes could be the original source of the new coronavirus outbreak in China<figure><img src="https://images.theconversation.com/files/311437/original/file-20200122-117907-1hdzuro.jpg?ixlib=rb-1.1.0&rect=10%2C1%2C1011%2C668&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Chinese cobra (_Naja atra_) with hood spread.</span> <span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/4/49/Naja_atra_%2803%29.jpg">Briston/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p><em>Editor’s note: Since publication of this article, the World Health Organization has said that there is “<a href="https://www.cnbc.com/2020/02/11/coronavirus-likely-jumped-from-bats-to-another-host-before-infecting-humans-who.html">no conclusive evidence</a>” that snakes were the source of the virus, although the exact viral intermediate host remains unknown.</em></p>
<p>Snakes – the <a href="https://onlinelibrary.wiley.com/doi/10.1002/jmv.25682">Chinese krait and the Chinese cobra</a> – may be the original source of the <a href="https://www.nytimes.com/2020/01/08/health/china-pneumonia-outbreak-virus.html">newly discovered coronavirus</a> that has triggered an outbreak of a deadly infectious respiratory illness in China this winter. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/311421/original/file-20200122-117907-ux3ndn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/311421/original/file-20200122-117907-ux3ndn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/311421/original/file-20200122-117907-ux3ndn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/311421/original/file-20200122-117907-ux3ndn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/311421/original/file-20200122-117907-ux3ndn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/311421/original/file-20200122-117907-ux3ndn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/311421/original/file-20200122-117907-ux3ndn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/311421/original/file-20200122-117907-ux3ndn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The many-banded krait (<em>Bungarus multicinctus</em>), also known as the Taiwanese krait or the Chinese krait, is a highly venomous species of elapid snake found in much of central and southern China and Southeast Asia.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/0/01/Bungarus_multicinctus_2.jpg">Briston/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The illness was first reported in late December 2019 in Wuhan, a major city in central China, and has been rapidly spreading. Since then, sick travelers from Wuhan have infected people in China and other countries, <a href="https://www.washingtonpost.com/health/2020/01/21/coronavirus-us-case/">including the United States</a>. </p>
<p>Using samples of the virus isolated from patients, scientists in China have determined the genetic code of the virus and used microscopes to photograph it. The pathogen responsible for this pandemic is a new coronavirus. It’s in the same family of viruses as the well-known <a href="https://www.cdc.gov/sars/index.html">severe acute respiratory syndrome coronavirus</a> (SARS-CoV) and <a href="https://www.cdc.gov/coronavirus/mers/index.html">Middle East respiratory syndrome coronavirus</a> (MERS-CoV), which have killed hundreds of people in the past 17 years. The World Health Organization (WHO) has named the <a href="https://www.cdc.gov/coronavirus/2019-ncov/index.html">new coronavirus 2019-nCoV</a>. </p>
<p><a href="https://www.livercenter.pitt.edu/people/faculty/haitao-guo-phd">We are</a> <a href="https://www.researchgate.net/scientific-contributions/2072638430_Guangxiang_George_Luo">virologists</a> and <a href="https://www.isb.pitt.edu/people/faculty/shou-jiang-sj-gao-phd">journal editors</a> and are closely following this outbreak because there are many questions that need to be answered to curb the spread of this public health threat.</p>
<h2>What is a coronavirus?</h2>
<p>The name of coronavirus comes from its shape, which resembles a crown or solar corona when imaged using an electron microscope. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/311436/original/file-20200122-117911-1w277st.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/311436/original/file-20200122-117911-1w277st.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/311436/original/file-20200122-117911-1w277st.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/311436/original/file-20200122-117911-1w277st.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/311436/original/file-20200122-117911-1w277st.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/311436/original/file-20200122-117911-1w277st.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/311436/original/file-20200122-117911-1w277st.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/311436/original/file-20200122-117911-1w277st.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The electron microscopic image, reveals the crown shape structural details for which the coronavirus was named. This image is of the Middle East respiratory syndrome coronavirus (MERS-CoV).</span>
<span class="attribution"><a class="source" href="https://phil.cdc.gov/Details.aspx?pid=18114">National Institute of Allergy and Infectious Diseases (NIAID)</a></span>
</figcaption>
</figure>
<p>Coronavirus is transmitted through the air and primarily infects the upper respiratory and gastrointestinal tract of mammals and birds. Though most of the members of the coronavirus family only cause mild flu-like symptoms during infection, <a href="https://www.cdc.gov/sars/about/index.html">SARS-CoV</a> and <a href="https://www.cdc.gov/coronavirus/mers/about/symptoms.html">MERS-CoV</a> can infect both upper and lower airways and cause severe respiratory illness and other complications in humans. </p>
<p>This new 2019-nCoV causes similar symptoms to SARS-CoV and MERS-CoV. People infected with these coronaviruses suffer a severe inflammatory response. </p>
<p>Unfortunately, there is <a href="https://www.cdc.gov/coronavirus/about/prevention.html">no approved vaccine</a> or antiviral treatment available for coronavirus infection. A better understanding of the life cycle of 2019-nCoV, including the source of the virus, how it is transmitted and how it replicates are needed to both prevent and treat the disease.</p>
<h2>Zoonotic transmission</h2>
<p>Both SARS and MERS are classified as zoonotic viral diseases, meaning the first patients who were infected acquired these viruses directly from animals. This was possible because while in the animal host, the virus had acquired a series of genetic mutations that allowed it to infect and multiply inside humans.</p>
<p>Now these viruses can be transmitted from person to person. Field studies have revealed that the original source of <a href="http://doi.org/10.1126/science.1118391">SARS-CoV and MERS-CoV is the bat</a>, and that the <a href="http://doi.org/10.1126/science.1087139">masked palm civets</a> (a mammal native to Asia and Africa) and <a href="http://doi.org/10.1016/S1473-3099(13)70164-6">camels</a>, respectively, served as intermediate hosts between bats and humans. </p>
<p>In the case of this 2019 coronavirus outbreak, <a href="https://www.nytimes.com/2020/01/21/world/asia/china-coronavirus-wuhan.html">reports state</a> that most of the first group of patients hospitalized were workers or customers at a local seafood wholesale market which also sold processed meats and live consumable animals including poultry, donkeys, sheep, pigs, camels, foxes, badgers, bamboo rats, hedgehogs and reptiles. However, since no one has ever reported finding a coronavirus infecting aquatic animals, it is plausible that the coronavirus may have originated from other animals sold in that market. </p>
<p>The hypothesis that the 2019-nCoV jumped from an animal at the market is strongly supported <a href="https://doi.org/10.1002/jmv.25682">by a new publication</a> in the Journal of Medical Virology. The scientists conducted an analysis and compared the genetic sequences of 2019-nCoV and all other known coronaviruses. </p>
<p>The study of the genetic code of 2019-nCoV reveals that the new virus is most closely related to two bat SARS-like coronavirus samples from China, initially suggesting that, like SARS and MERS, the bat might also be the origin of 2019-nCoV. The authors further found that the viral RNA coding sequence of 2019-nCoV spike protein, which forms the “crown” of the virus particle that recognizes the receptor on a host cell, indicates that the bat virus might have mutated before infecting people. </p>
<p>But when the researchers performed a more detailed bioinformatics analysis of the sequence of 2019-nCoV, it suggests that this <a href="https://doi.org/10.1002/jmv.25682">coronavirus might come from snakes</a>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/311411/original/file-20200122-117917-q9l5o5.jpg?ixlib=rb-1.1.0&rect=0%2C25%2C4132%2C2659&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/311411/original/file-20200122-117917-q9l5o5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/311411/original/file-20200122-117917-q9l5o5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/311411/original/file-20200122-117917-q9l5o5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/311411/original/file-20200122-117917-q9l5o5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/311411/original/file-20200122-117917-q9l5o5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/311411/original/file-20200122-117917-q9l5o5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Wuhan Huanan Wholesale Seafood Market, where the coronavirus outbreak is believed to have started, is now closed.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/China-Outbreak/6cafa23497f74bb5a5b54500c9625e5a/3/0">AP Photo/Dake Kang</a></span>
</figcaption>
</figure>
<h2>From bats to snakes</h2>
<p>The researchers used an <a href="https://doi.org/10.1002/jmv.25682">analysis of the protein codes</a> favored by the new coronavirus and compared it to the protein codes from coronaviruses found in different animal hosts, like birds, snakes, marmots, hedgehogs, manis, bats and humans. Surprisingly, they found that the protein codes in the 2019-nCoV are most similar to those used in snakes. </p>
<p>Snakes often hunt for bats in wild. Reports indicate that <a href="https://www.japantimes.co.jp/news/2020/01/21/asia-pacific/coronavirus-china-food-markets/#.Xiiibi2ZMnc">snakes were sold in the local seafood market</a> in Wuhan, raising the possibility that the 2019-nCoV might have jumped from the host species – bats – to snakes and then to humans at the beginning of this coronavirus outbreak. However, how the virus could adapt to both the cold-blooded and warm-blooded hosts remains a mystery. </p>
<p><a href="https://onlinelibrary.wiley.com/doi/10.1002/jmv.25683">The authors of the report and other researchers must verify the origin of the virus</a> through laboratory experiments. Searching for the 2019-nCoV sequence in snakes would be the first thing to do. However, since the outbreak, the seafood market has been disinfected and shut down, which makes it challenging to trace the new virus’ source animal. </p>
<p>Sampling viral RNA from animals sold at the market and from wild snakes and bats is needed to confirm the origin of the virus. Nonetheless, the reported findings will also provide insights for developing prevention and treatment protocols.</p>
<p>The 2019-nCoV outbreak is another reminder that people should limit the consumption of wild animals to <a href="https://www.cdc.gov/onehealth/basics/zoonotic-diseases.html">prevent zoonotic infections</a>. </p>
<p><em>This article has been updated to clarify that the genetic material from the virus was RNA, not DNA.</em></p>
<p>[ <em>You’re smart and curious about the world. So are The Conversation’s authors and editors.</em> <a href="https://theconversation.com/us/newsletters/weekly-highlights-61?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=weeklysmart">You can get our highlights each weekend</a>. ]</p><img src="https://counter.theconversation.com/content/130364/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Haitao Guo is an associate editor of the Journal of Medical Virology. </span></em></p><p class="fine-print"><em><span>Guangxiang “George” Luo is the Deputy Editor-in-Chief of the Journal of Medical Virology.
</span></em></p><p class="fine-print"><em><span>Shou-Jiang Gao is the Editor-in-Chief of the Journal of Medical Virology. </span></em></p>A new coronavirus related to SARS and MERS has now traveled from China to the United States. A genetic analysis reveals that this deadly pathogen may have originated in snakes.Haitao Guo, Professor of Microbiology and Molecular Genetics, University of PittsburghGuangxiang “George” Luo, Professor of Microbiology, University of Alabama at BirminghamShou-Jiang Gao, Professor of Microbiology and Molecular Genetics, University of PittsburghLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/689322016-12-15T16:07:45Z2016-12-15T16:07:45ZHow your Christmas turkey arrives already stuffed – with antibiotics<figure><img src="https://images.theconversation.com/files/150113/original/image-20161214-32212-1m7gel4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Gobbled up.</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-523092337/stock-photo-drogheda-ireland-23112016-free-range-turkeys-pictured-on-mcevoys-farm-in-termonfeckin-drogheda-co-louth-ireland-ahead-of-the-festive-season.html?src=UkDTg-orcmbVmeas92y2Yw-3-67">Shutterstock</a></span></figcaption></figure><p>You may consider the turkey to be a traditional part of your Christmas celebrations. But however you cook it, something about this festive bird is changing – it’s getting fatter.</p>
<p>The average turkey <a href="http://www.economist.com/node/14959618">now weighs in at more than 10kg</a>, a much bigger animal than its wild ancestor. And, while this has partly been achieved by more sophisticated genetics and husbandry, the use of antibiotics has also played a key role. Stopping the spread of disease in animal production is an important way of delivering welfare – and a healthy turkey gains weight more quickly.</p>
<p>The trouble is that antibiotics are often the first line of attack in both preventing and treating animal diseases. And just as it does in humans, over use of antibiotics has resulted in the emergence of more antimicrobial resistance in the organisms which cause bacterial and fungal diseases. </p>
<p>Many of the antibiotics used in farming are also used in treating human diseases – and the transfer of resistant bacteria through our food supply chain does occur. <em>Staphylococcus aureus</em> and <em>E. coli</em>, are organisms which can be harmless in both animal and human environments – but it is their antibiotic resistant variants that are of major concern to us. <em>Staphylococcus aureus</em> can cause blood poisoning and its methicillin-resistant form (MRSA) is known as the “superbug”. Antibiotic resistant forms of <em>E.coli</em> such as <em>E.coli o157</em> cause severe sickness.</p>
<p>Antimicrobial resistance in livestock farming will reduce the impact of the suite of pharmaceuticals we rely on for fighting human diseases. It is a threat which has been highlighted by <a href="https://www.theguardian.com/environment/2016/oct/03/revealed-mrsa-variant-found-in-british-pork-at-asda-and-sainsburys">revelations that MRSA variants have been found in pork sold in UK supermarkets</a>. </p>
<p>We urgently need a greater awareness of the risks associated with administering antimicrobial treatments on livestock farms and a better understanding of what products are being used. For while the antibiotic-resistant superbugs plaguing hospital wards have been well documented in the media, the <a href="https://amr-review.org/">similar epidemic</a> in livestock farming has been much less well publicised.</p>
<p>How we choose to source meat is an important factor dealing with this risk – and it is not just turkey production that has changed significantly in recent years. Pigs represent the greatest amount of livestock produced globally – China produces <a href="http://www.fao.org/faostat/en/#home">54m tonnes of pork each year</a>. This is 17% of global meat production and represents a huge pressure point for the use of antimicrobial treatments. </p>
<p>In November 2015, Chinese scientists declared they were on the cusp of the “<a href="http://www.bbc.co.uk/news/health-34857015">post-antibiotic era</a>” after bacteria resistant to the antibiotic used when all others have failed, <a href="https://theconversation.com/is-the-antibiotic-apocalypse-nigh-51006">colistin</a>, were found on livestock farms. This caused the global community to sit up and take note – before everyone went back to business as usual, with demand and production of meat <a href="http://www.fao.org/docrep/005/y4252e/y4252e05b.htm">continuing to rise</a>.</p>
<p>The problem is that we do not know how often – or how many – antimicrobial treatments are used in global farming. There are big gaps in our data and understanding. What we do know is that a considerable amount of antibiotic material is used in rearing healthy animals to be free of infection. An <a href="https://amr-review.org/">independent study</a> reported the amount of antimicrobials used in food production in the UK is at least the same as that in humans. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/150320/original/image-20161215-26027-1ngyysn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/150320/original/image-20161215-26027-1ngyysn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/150320/original/image-20161215-26027-1ngyysn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/150320/original/image-20161215-26027-1ngyysn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/150320/original/image-20161215-26027-1ngyysn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/150320/original/image-20161215-26027-1ngyysn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/150320/original/image-20161215-26027-1ngyysn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Time for turkey.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/pic-511486225/stock-photo-roasted-turkey-for-christmas-day.html?src=6I0WMK6LHMHM0NVEdW4zTg-1-77">Shutterstock</a></span>
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</figure>
<p>The requirement for antibiotics is not in doubt here – and, when they are properly used for treating infections, the outcomes are <a href="https://wellcome.ac.uk/sites/default/files/evidence-for-action-on-antimicrobial-resistance-wellcome-sep16.pdf">positive</a>. But other countries have shown that the need for using antimicrobials can be reduced by detecting diseases more effectively and by considering different management practices. </p>
<h2>Farming changes</h2>
<p>In the <a href="https://amr-review.org/sites/default/files/Antimicrobials%20in%20agriculture%20and%20the%20environment%20-%20Reducing%20unnecessary%20use%20and%20waste.pdf">Netherlands and Denmark</a> changes have been introduced since 1995 which focus on producers working with public health agencies. This stronger relationship identified where greater surveillance and the application of resistance detection would be most likely to succeed. This has led to 50% reductions in antimicrobial use in pork meat and ten-fold reductions in their use in poultry production. Improvements in animal housing, disease detection and resistance detection that have been initiated by these programmes have also enhanced trust across the food supply chain.</p>
<p>The role of livestock farming in tackling antimicrobial resistance must be linked to animal welfare. If production practices can reduce the misuse of antimicrobial treatments, then strong government policy must help to make this happen. This year the UK government <a href="http://www.farminguk.com/News/Defra-scrap-plans-to-devolve-animal-welfare-codes_39314.html">halted plans to devolve responsibility</a> for the codes of practice in livestock farming because of this type of issue. At a time when a coordinated approach to tackling antimicrobial resistance is most needed, it is critical for farmers and policymakers to work together and fully understand the issues at stake. </p>
<p>Animal welfare is important – and antibiotics help to provide it. But it would be catastrophic if they were to lose their effectiveness through overuse. Then the <a href="https://theconversation.com/is-the-antibiotic-apocalypse-nigh-51006">post-antibiotic era</a> really would have arrived – when minor infections become lethal.</p><img src="https://counter.theconversation.com/content/68932/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Wayne Martindale receives funding from Innovate UK. </span></em></p>The rise in size of your festive bird hides a chemical concern.Wayne Martindale, Senior Research Fellow, Corporate Social Responsibility, Sheffield Hallam UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/682252016-11-07T23:40:54Z2016-11-07T23:40:54ZAustralian law needs a refresher on the science of HIV transmission<figure><img src="https://images.theconversation.com/files/144765/original/image-20161107-4694-ry4k7e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Recent improvements in medical management of HIV infection are not well understood in the legal sector. </span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/pic-309710009/stock-photo-image-concept-with-the-result-of-the-hiv-test.html?src=jsZ4xp3vaVRNZ8nFK-ccCw-1-3">www.shutterstock.com </a></span></figcaption></figure><p>Being diagnosed with HIV is a confronting experience. </p>
<p>However the stigma associated with HIV infection – a hangover from its social and medical history – is responsible for an exaggerated perception of transmission risk through sex, and the harms of living with HIV infection. </p>
<p>In our <a href="https://www.mja.com.au/journal/2016/205/9/sexual-transmission-hiv-and-law-australian-medical-consensus-statement">consensus statement published this week in the Medical Journal of Australia</a>, we detail the latest evidence on HIV transmission risk and recent advances in HIV prevention and treatment.</p>
<p>We propose that legal cases relating to HIV transmission should be considered in light of such evidence, and that alternatives to prosecution such as the public health management approach are often appropriate. </p>
<h2>HIV infection no longer a death sentence</h2>
<p>There have been many advances in HIV diagnosis, prevention and treatment since the identification of the first AIDS cases in the early 1980s. </p>
<p>In the initial days of the AIDS epidemic, patients would, after a number of years, develop serious infections and other illnesses due to their immune deficiency, usually resulting in death. When the first treatments became available, they bought time but often at the cost of serious medication side-effects, and complicated treatment regimens involving many tablets each day.</p>
<p>While it remains a serious infection, HIV is now a disease that can be effectively managed through medical treatment, regular health monitoring and healthy lifestyle. For many people with HIV, treatment involves taking only a single pill each day. Those taking antiviral therapy can expect to live a normal life, in good health, with a life expectancy similar to their HIV-negative counterparts. </p>
<p>These great improvements, familiar to those working in health, are not as well understood in the legal sector. </p>
<h2>Prosecutions for HIV infection</h2>
<p>Unlike other diseases, HIV has a long and uneasy relationship with criminal law. In the early years of the epidemic, the stigma around HIV, the fact that it was almost always fatal, and unfounded fears about its potential use as a weapon led to the criminalisation of HIV transmission and exposure. </p>
<p>Since 1991, there have been more than 38 criminal prosecutions for HIV transmission or exposure during sex in Australia. Despite the significant improvements in health and longevity of people living with HIV, the rate of criminal prosecutions has not decreased. </p>
<p>The courts have shown an understanding of the effectiveness of condoms: no one who has used condoms has been convicted. However, people continue to be prosecuted, including for “exposing” others to the risk of HIV infection, even in the absence of actual transmission. This occurs despite the relatively low per-act risk of HIV transmission and the fact that for most people the harms of HIV infection are far less serious than they once were.</p>
<h2>New approaches to limit HIV transmission</h2>
<p>HIV is actually difficult to transmit. <a href="https://www.mja.com.au/journal/2016/205/9/sexual-transmission-hiv-and-law-australian-medical-consensus-statement">Sexual transmission occurs</a> during only about 1% (or less) of penetrative sexual encounters, even when a condom is not used and the HIV-positive person is not on treatment.</p>
<p>HIV prevention messaging in the early days of the epidemic focused on sexual abstinence and condom use. However, prevention messaging is now more nuanced and has expanded to include new ways of reducing HIV transmission risk. A not insignificant number of people at risk of HIV infection choose to have sex without using a condom, which is why developing alternative methods of HIV prevention have been prioritised in recent years. Such research has delivered game-changing results: “treatment as prevention” and “pre-exposure prophylaxis”. </p>
<p><a href="http://www.nejm.org/doi/full/10.1056/NEJMoa1105243">Treatment as prevention</a> refers to the greatly reduced risk of HIV transmission as a result of HIV-positive people taking antiviral treatment, which suppresses replication of the virus in the infected person’s body. When a person with HIV has a very low viral load (unmeasurable levels of HIV in the blood), the risk of sexual transmission becomes <a href="https://www.ncbi.nlm.nih.gov/pubmed/27404185">very low</a>. In fact, there has never been a documented case of HIV transmission from a person with an undetectable viral load.</p>
<p><a href="http://www.nejm.org/doi/full/10.1056/NEJMoa1011205">Pre-exposure prophylaxis</a> describes the use of antiviral medication by an HIV-negative person as a way of preventing HIV infection. Pre-exposure prophylaxis is a <a href="http://www.nejm.org/doi/full/10.1056/NEJMoa1506273">very effective means</a> of preventing HIV transmission, with only isolated cases of transmission identified among people applying this approach. This groundbreaking new strategy is available in Australia via limited pilot programs, and is being evaluated for Pharmaceutical Benefits Scheme listing.</p>
<h2>How the law treats people with HIV</h2>
<p>Criminal laws relating to HIV transmission and exposure vary from state to state, but a common factor is that people with HIV are expected to take “reasonable precautions” to prevent transmission. Condom use has long been accepted as meeting this threshold. </p>
<p>The evidence now supports acceptance of treatment as prevention (for the positive partner) and/or pre-exposure prophylaxis (for the negative partner) as meeting the same standard. And the limited harms of HIV infection as a consequence of acts involving low to negligible risk of transmission mean HIV cases generally do not belong in criminal courts.</p>
<p>There is an alternative. All states and territories have health protocols for managing allegations of risky behaviour. This public health approach – involving education, case management and, where required, behavioural orders and isolation – is a much more effective way of protecting public health.</p>
<p>As researchers and clinicians, we are intimately aware of the impact an HIV diagnosis can have. We have all supported patients coming to terms with an HIV diagnosis; many of us having had the painful task of delivering that devastating news. </p>
<p>The criminal law has a role to play, particularly should there ever be a case where a person deliberately transmits HIV. </p>
<p>However, with the advances of recent years in both prevention and treatment, authorities need to be more familiar with latest scientific and medical evidence, and consider alternatives to prosecution such as the public health management approach.</p>
<hr>
<p><em>Elizabeth Crock, <a href="http://www.ashm.org.au/">Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine</a>, co-authored the <a href="https://www.mja.com.au/journal/2016/205/9/sexual-transmission-hiv-and-law-australian-medical-consensus-statement">consensus statement</a>.</em></p><img src="https://counter.theconversation.com/content/68225/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Grulich has given expert evidence in legal cases involving HIV transmission. </span></em></p><p class="fine-print"><em><span>Nothing to disclose.</span></em></p><p class="fine-print"><em><span>David Cooper, David Nolan, Levinia Crooks, Mark Boyd, Michelle Giles, and Sharon Lewin do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>HIV diagnosis is devastating for patients and their families. But the infection is no longer a death sentence, and should not be prosecuted as such say experts.Mark Boyd, Professor, Chair of Medicine, University of AdelaideAndrew Grulich, Professor and Program Head, UNSW SydneyDavid Cooper, Scientia Professor of Medicine and Director, Kirby Institute, UNSW SydneyDavid Nolan, Adjunct Professor, Institute for Immunology and Infectious Disease , Murdoch UniversityLevinia Crooks, Adjunct Associate Professor, La Trobe UniversityMichelle Giles, Associate Professor, Department of infectious diseases and Dept of Obstetrics and gynaecology, Monash UniversitySharon Lewin, Director, The Peter Doherty Institute for Infection and Immunity, The University of Melbourne and Royal Melbourne Hospital and Consultant Physician, Department of Infectious Diseases, Alfred Hospital and Monash University, The Peter Doherty Institute for Infection and ImmunityTrent Yarwood, Infectious Diseases Physician, Senior Lecturer, James Cook University and, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.