tag:theconversation.com,2011:/nz/topics/vectors-22212/articlesVectors – The Conversation2023-12-13T10:59:52Ztag:theconversation.com,2011:article/2197232023-12-13T10:59:52Z2023-12-13T10:59:52ZClimate change risks triggering a spike in infectious disease outbreaks: three reasons why<p>Climate change is our planet’s most immediate existential threat, and will likely only worsen for the foreseeable future. </p>
<p>Among its numerous adverse effects on human health, there is strong evidence linking climate change to <a href="https://www.science.org/doi/10.1126/science.1239401">infectious disease</a> outbreaks. </p>
<p>A recent analysis revealed that of 375 infectious diseases affecting human beings, 218 <a href="https://www.nature.com/articles/s41558-022-01426-1">(58%)</a> can be aggravated by climatic hazards. </p>
<p>It is no longer a question of “if”, but “when” an epidemic will be triggered or amplified by climate events.</p>
<p>It’s vital that swift, decisive action is taken to mitigate the impending public health crisis worsened by climate change. </p>
<p>We are part of the <a href="https://climade.health/">Climate Amplified Diseases and Epidemics consortium</a> launched in early 2023. The consortium is made up of leading molecular biologists, epidemiologists, ecologists and evolutionary biologists. </p>
<p>We engaged with hundreds of scientists from around the world to compile a report, the <a href="https://climade.health/cop28-report">Climate Change and Epidemics 2023 Synthesis</a>, which was launched in Dubai at COP28.</p>
<p>The team members who led the compilation of the report are from the <a href="https://climade.health/wp-content/uploads/2023/11/CLIMADE_COP28Report.pdf">global south</a>.
This is important, as the global south is likely to suffer the largest health effects from climate change.</p>
<p>The report identified three main reasons why climate change may aggravate infectious diseases.</p>
<ul>
<li><p>Increases in temperature and changes in <a href="https://ugc.berkeley.edu/background-content/precipitation/">precipitation patterns</a> create conditions for disease vectors, such as mosquitoes, to flourish and expand their distribution ranges.</p></li>
<li><p>More frequent extreme climatic events such as floods can cause surges of infections, for example by contaminating drinking water with faecal matter.</p></li>
<li><p>Climate-driven migration by people and their livestock can trigger outbreaks of infectious diseases.</p></li>
</ul>
<h2>How are diseases linked to climate change?</h2>
<p>Rising temperatures may create environments conducive for the spread of certain types of pathogens and their vectors. </p>
<p>For example, rising temperatures may increase the breeding rate of disease <a href="https://e360.yale.edu/features/dengue-fever-climate-change">vectors</a>, such as mosquitoes, and the infectious agents they carry, and expand their distribution ranges to new areas. </p>
<p><a href="https://www.health.ny.gov/diseases/communicable/arboviral/fact_sheet.htm#:%7E:text=Arboviral%20disease%20is%20a%20general,such%20as%20mosquitoes%20and%20ticks">Arboviruses</a>, which are transmitted by mosquitoes or ticks,
<a href="https://www.who.int/news-room/fact-sheets/detail/chikungunya#:%7E:text=Chikungunya%20is%20a%20mosquito%2Dborne,meaning%20%E2%80%9Cto%20become%20contorted%E2%80%9D.">chikungunya</a> and <a href="https://www.who.int/news-room/fact-sheets/detail/dengue-and-severe-dengue#:%7E:text=Overview,body%20aches%2C%20nausea%20and%20rash.">dengue</a> now occur in South Asia, South America and Europe in previously unaffected areas.</p>
<p><a href="https://www.nicd.ac.za/diseases-a-z-index/west-nile-fever/">West Nile virus</a> infections can now be acquired <a href="https://www.mdpi.com/1999-4915/12/4/448">north of the Alps</a>. </p>
<p>The changing climate increases the risk for many types of <a href="https://iopscience.iop.org/article/10.1088/2752-5295/ac6e7d/pdf">extreme events</a> such as floods, storms and droughts.</p>
<p>Extreme weather conditions often trigger the displacement of humans and animals, and impair the provision of essential supplies, medical care and transport. </p>
<p>This is particularly true of waterborne pathogens such as cholera. The world is currently in the <a href="https://www.who.int/emergencies/disease-outbreak-news/item/2023-DON437">seventh cholera pandemic</a>. </p>
<p>In 2022 and 2023, following two severe tropical storms causing widespread flooding and destruction, <a href="https://www.who.int/emergencies/disease-outbreak-news/item/2022-DON435">Malawi</a> experienced the deadliest outbreak of cholera in the country’s history. </p>
<p><a href="https://iopscience.iop.org/article/10.1088/2752-5295/ac6e7d/pdf">Droughts</a> also cause infection-related problems. People and their livestock may be forced to use unsafe water sources with higher concentrations of contaminants including water-borne pathogens. Hepatitis E outbreaks occur under conditions of <a href="https://www.who.int/news-room/fact-sheets/detail/hepatitis-e">water stress</a>.</p>
<p>Lastly, climate change may lead to large-scale displacement and migration of people and animals. The ongoing <a href="https://alliancebioversityciat.org/stories/el-nino-here-what-it-and-what-can-we-do">El Niño phenomenon</a> will likely produce severe drought in some regions of the world, potentially spurring mass temporary and permanent migrations. </p>
<p>This can lead to more and closer interactions with wildlife, which increases the risk of spillover of pathogens, including <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8182890/">novel ones</a>. </p>
<h2>Looking after the vulnerable</h2>
<p>Developing countries are more at risk of climate disasters. They also have <a href="https://climade.health/wp-content/uploads/2023/11/CLIMADE_COP28Report.pdf">less adaptive capacity</a> and preparedness to respond, leaving them highly vulnerable. </p>
<p>We call on governments, academic institutions and health organisations to expand genomic surveillance capabilities for early detection and to monitor the spread of infectious diseases. </p>
<p>Vulnerable communities are <a href="https://unfccc.int/sites/default/files/resource/Considerations%20regarding%20vulnerable.pdf">disproportionately affected</a> by climate change. These populations should be prioritised by investing in resilient healthcare systems and disaster preparedness measures. </p>
<h2>Saying no to ‘climate doomism’</h2>
<p>Rather than falling for <a href="https://yaleclimateconnections.org/2022/05/on-climate-doomism-heart-mind-reasons-to-resist-it/">“climate doomism”</a>, which tends to paralyse rather than trigger action, we prefer to learn from what has been achieved during the COVID-19 pandemic.</p>
<p>These achievements include novel epidemiological and infection control tools, including self-testing or smartphone apps, <a href="https://www.nicd.ac.za/diseases-a-z-index/disease-index-covid-19/surveillance-reports/weekly-reports/wastewater-based-epidemiology-for-sars-cov-2-in-south-africa/">wastewater epidemiology</a> and <a href="https://www.cdc.gov/coronavirus/2019-ncov/variants/genomic-surveillance.html#:%7E:text=Genomic%20Sequencing%3A%20Scientists%20use%20a,changes%20may%20affect%20public%20health.">genomic sequencing</a> to track the evolution of the agents that cause the disease.</p>
<p>Substantial capacity consisting of skilled people and adequate facilities has been built in much of the global south. This shows what is possible when the world works together. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/qi72DGfodJM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure><img src="https://counter.theconversation.com/content/219723/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Prof. Wolfgang Preiser receives funding from various scientific grant funders, directly and indirectly, incl. South African NRF, PRF, NHLS-RT and more. He is affiliated with the University of Stellenbosch and South African National Health Laboratory Service (NHLS).</span></em></p><p class="fine-print"><em><span>Tulio de Oliveira receives funding from the South African Medical Council, the Rockefeller Foundation, the National Insitute of Health (NIH), the European Commission and other charities and government funding agencies. He is affiliated with the Centre for Epidemic Response and Innovation (CERI), Stellenbosch University, South Africa and the Genomics Surveillance Unit (GSU), Wellcome Sanger Institute, U.K.</span></em></p><p class="fine-print"><em><span>Cheryl Baxter, Houriiyah Tegally, and Monika Moir 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>Heat, floods and droughts create conditions for pathogens and their vectors.Wolfgang Preiser, Head: Division of Medical Virology, Stellenbosch UniversityCheryl Baxter, Head Scientific Research Support, Stellenbosch UniversityHouriiyah Tegally, Senior Data Analyst, Head of Data Science at Centre for Epidemic Response and Innovation (CERI), Stellenbosch UniversityMonika Moir, Postdoctoral Researcher of Pathogen Genomics, Stellenbosch UniversityTulio de Oliveira, Director: KRISP - KwaZulu-Natal Research and Innovation Sequencing Platform, University of KwaZulu-NatalLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2085382023-09-21T21:27:36Z2023-09-21T21:27:36ZLyme disease: The pathogen’s cunning strategies for persistent infection offer clues for vaccine development<figure><img src="https://images.theconversation.com/files/547386/original/file-20230911-25-n5os9t.JPG?ixlib=rb-1.1.0&rect=65%2C23%2C1709%2C1158&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The black-legged tick is the vector that spreads Lyme disease. Its bite can infect humans with the Borrelia burgdorferi bacterium.</span> <span class="attribution"><span class="source">(Jim Gathany/CDC)</span></span></figcaption></figure><iframe style="width: 100%; height: 100px; border: none; position: relative; z-index: 1;" allowtransparency="" allow="clipboard-read; clipboard-write" src="https://narrations.ad-auris.com/widget/the-conversation-canada/lyme-disease-the-pathogens-cunning-strategies-for-persistent-infection-offer-clues-for-vaccine-development" width="100%" height="400"></iframe>
<p>Lyme disease is the leading <a href="https://www.who.int/news-room/fact-sheets/detail/vector-borne-diseases">vector-borne disease</a> — meaning diseases that are transmitted to humans from another organism like a tick or mosquito — in <a href="https://doi.org/10.1186/s12889-019-7069-6">North America and Europe</a>. </p>
<p><a href="https://doi.org/10.3201/eid2702.202731">New human cases are estimated</a> at over <a href="http://dx.doi.org/10.15585/mmwr.ss6622a1">400,000 in the United States each year</a>. Canada has experienced a drastic increase in human cases, <a href="https://www.canada.ca/en/public-health/services/diseases/lyme-disease/surveillance-lyme-disease.html#a5">from 266 cases in 2011 to 3,147 in 2021</a>, as the habitat of its vector, a tick, expands north. </p>
<p>The initial symptoms of human Lyme disease can be vague, such as fever, headache, fatigue and often rash. It is a potentially serious condition that can affect multiple systems in the body — including the heart, nervous system and joints — and can become a chronic illness.</p>
<p>Lyme disease is caused by a unique, spiral-shaped (spirochete) bacterium called <a href="https://doi.org/10.1099/00207713-34-4-496"><em>Borrelia burgdorferi</em></a>. <em>B. burgdorferi</em> cannot survive in the environment on its own. For <a href="https://doi.org/10.21775/cimb.042.473">survival and transmission</a>, it requires susceptible hosts (usually small mammals or birds) and a <a href="https://doi.org/10.1056/NEJM198303313081301">specific vector</a>: the black-legged tick, also called the deer tick.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/535388/original/file-20230703-257464-m0lz6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/535388/original/file-20230703-257464-m0lz6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=420&fit=crop&dpr=1 600w, https://images.theconversation.com/files/535388/original/file-20230703-257464-m0lz6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=420&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/535388/original/file-20230703-257464-m0lz6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=420&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/535388/original/file-20230703-257464-m0lz6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=528&fit=crop&dpr=1 754w, https://images.theconversation.com/files/535388/original/file-20230703-257464-m0lz6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=528&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/535388/original/file-20230703-257464-m0lz6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=528&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Lyme disease infectious cycle: Adult ticks lay egg sacs that can hatch thousands of tick larvae. Larvae are not born with Borrelia burgdorferi but can acquire the bacterium when they feed on an infected host. After feeding, larvae molt to nymphs which must feed once to molt to adults. Female adult ticks also feed once before laying the egg sac. Nymphs and adult ticks can transmit B. burgdorferi to susceptible hosts while feeding.</span>
<span class="attribution"><span class="source">(BioRender)</span></span>
</figcaption>
</figure>
<h2>Evading the immune system</h2>
<p><em>B. burgdorferi</em> must survive extremely diverse conditions over the course of its transmission and infection cycle: from host to tick vector, and then into new hosts. </p>
<p>This bacterium senses and responds to its surroundings, most notably by <a href="https://doi.org/10.1128/iai.70.7.3382-3388.2002">modifying its appearance</a> by changing the <a href="https://doi.org/10.1073/pnas.92.7.2909" title="). _B. burgdorferi_ has over [50 surface-exposed proteins](https://doi.org/10.1128/jb.00658-16 "">proteins on its outer surface</a> to <a href="https://doi.org/10.1111/j.1574-695X.2012.00980.x">help it survive</a> in either <a href="https://doi.org/10.1038/s41467-023-35897-3">the tick</a> or the host.</p>
<p>When a tick infected by <em>B. burgdorferi</em> bites and feeds on a vertebrate host, it provides a signal for the bacteria to switch its proteins to those required to infect the host, and to begin migrating through the tick and into the bite site. This process takes between <a href="https://doi.org/10.4269/ajtmh.1995.53.397">36 and 72 hours</a>. </p>
<p>However, many of these proteins are recognized by the host as foreign, and the host’s immune system works to try to clear the infection. This includes a strong, antibody response targeted against <em>B. burgdorferi</em>. </p>
<p>Despite these immune responses, <em>B. burgdorferi</em> is able to cause long-term infections. In natural host reservoirs — the animals that the bacterium usually finds itself in via tick bites, such as small rodents — these infections do not cause diseases like those seen in humans and other <a href="https://doi.org/10.1016/j.idc.2007.12.013">non-natural reservoirs</a>. </p>
<p>In fact, the bacteria itself does not produce any products that would be <a href="https://doi.org/10.1016/j.cll.2015.07.004">toxic to its hosts</a>, either natural or non-natural. Yet chronic infection in humans can lead to <a href="https://doi.org/10.1038/nrdp.2016.90">Lyme neuroborreliosis, carditis and Lyme arthritis</a>.</p>
<figure class="align-center ">
<img alt="Bacteria that look like bright green and yellow squiggles against a dark green background" src="https://images.theconversation.com/files/548570/original/file-20230915-23-4ysjok.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548570/original/file-20230915-23-4ysjok.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=612&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548570/original/file-20230915-23-4ysjok.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=612&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548570/original/file-20230915-23-4ysjok.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=612&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548570/original/file-20230915-23-4ysjok.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=770&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548570/original/file-20230915-23-4ysjok.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=770&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548570/original/file-20230915-23-4ysjok.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=770&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Microscopic image of Lyme disease bacteria Borrelia burgdorferi. In this photo, immunofluorescent antibodies have been used to change the colour of spirochetes that express different outer surface proteins.</span>
<span class="attribution"><span class="source">(NIAID)</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>How then, are these bacteria able to cause such a devastating disease in humans and other animals, but not in their natural host reservoirs?</p>
<p>While there is still much to learn about <em>B. burgdorferi</em>, we know of several factors that play a role in the <a href="https://doi.org/10.1038/nrdp.2016.90">range of disease it causes</a>. These include:</p>
<ul>
<li>its genetic make-up, </li>
<li>its ability to access various tissues (such as the joints, heart and nervous system) due to its <a href="https://doi.org/10.1128/iai.01228-12">ability to move around (motility)</a>, and </li>
<li>the immune response of the host. </li>
</ul>
<p>Apart from motility, <em>B. burgdorferi</em> also protects itself from the strong <em>B. burgdorferi</em>-specific targeted antibody response of its host’s immune system by changing the appearance of the main outer surface protein expressed during persistent infection in a process called <a href="https://doi.org/10.1128/iai.66.8.3698-3704.1998">antigenic variation</a>.</p>
<h2>How Lyme disease is perpetuated</h2>
<p>In addition to antigenic variation, <em>B. burgdorferi</em> bacteria can also change their DNA by <a href="https://doi.org/10.1073/pnas.0402745101">exchanging genetic information, a process also known as gene transfer</a>. This process allows these bacteria to further alter their <a href="https://doi.org/10.1128/mbio.00153-10">appearance</a> <a href="https://doi.org/10.1534/genetics.111.130773">during infection</a> to avoid the host immune system.</p>
<p>This process works so well that these <em>B. burgdorferi</em> bacteria appear different enough to allow <a href="https://doi.org/10.7326/0003-4819-127-2-199707150-00006">re-infection</a> or even <a href="https://doi.org/10.1128/iai.01817-14">co-infection</a> (where multiple strains of B. burgdorferi infect a single host at the same time) of a vertebrate host, like a mouse or a human, despite the presence of specific antibodies to fight the bacterium.</p>
<p>In fact, in nature, the majority of host reservoirs and the ticks that carry the bacterium are infected with <a href="https://doi.org/10.1128/AEM.02296-15">multiple strains of <em>B. burgdorferi</em></a>. The ability of <em>B. burgdorferi</em> to reinfect and co-infect both ticks and hosts increases the spread of the bacteria in the environment as well as the chances that humans will encounter Lyme disease.</p>
<h2>Human cases of Lyme disease are increasing</h2>
<p>As a vector-borne pathogen, <em>B. burgdorferi</em> only infects individuals that are bitten by an infected tick. It is not transmitted from <a href="https://doi.org/10.1093/cid/ciz872">person to person</a>.</p>
<p>Environments that support black-legged/deer ticks are at risk of harbouring <em>B. burgdorferi</em>. In North America, these species of ticks are widely distributed throughout the eastern and midwestern United States. Recent <a href="https://doi.org/10.1093/jme/tjy104">geographic expansion</a> to the north is increasing the prevalence of Lyme disease <a href="https://doi.org/10.1503/cmaj.080148">in Canada</a>. </p>
<p>The increase of human Lyme disease cases highlights the failure of existing preventive strategies — such as minimizing exposure to tick habitats, performing diligent tick checks, and wearing suitable clothing when performing activities in known tick habitats — and emphasizes the need for an effective <a href="https://doi.org/10.21775/cimb.042.191">human vaccine</a>.</p>
<h2>A One Health approach</h2>
<p>At <a href="https://www.vido.org/">Vaccine and Infectious Disease Organization</a> at the University of Saskatchewan, we are taking a <a href="https://ipac-canada.org/one-health">One Health</a> approach by recognizing that human health is closely related to the health of animals and the shared environment. We are investigating the role of <em>B. burgdorferi</em>, ticks, and susceptible animals on the spread and survival of the Lyme disease bacterium. </p>
<p>It is important to mimic the natural infectious cycle as much as possible when identifying potential vaccine and drug targets. This is because the way host animals are infected (for example, artificial needle infection or natural tick bite) can produce drastic differences in the resulting infection. </p>
<p>Additionally, despite the prevalence of this disease, there are still many aspects of the infectious cycle that remain unknown due to the uniqueness of <em>B. burgdorferi</em> and a lack of knowledge about the tick vector. </p>
<p>For example, we recently learned that a <em>B. burgdorferi</em> protein is responsible for regulating the components necessary for the bacterium to infect vertebrates, including humans. The absence of this protein, among other things, leads to the <a href="https://doi.org/10.1038/s41467-023-35897-3">death of <em>B. burgdorferi</em> in ticks</a>, making it an exciting target for research investigation. </p>
<p>By learning more about the molecular mechanisms that change or reduce the severity of the disease caused by this bacterium, we can identify new targets for the prevention of human Lyme disease.</p><img src="https://counter.theconversation.com/content/208538/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jenny Wachter 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 bacterium that causes Lyme disease is a master of disguise, changing its appearance to evade the immune system as it moves from the ticks that carry it to humans or animals.Jenny Wachter, Research scientist/Adjunct professor, University of SaskatchewanLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2068592023-06-11T20:53:06Z2023-06-11T20:53:06ZHas a mathematician solved the ‘invariant subspace problem’? And what does that even mean?<figure><img src="https://images.theconversation.com/files/530505/original/file-20230607-21-zjfgrl.jpg?ixlib=rb-1.1.0&rect=0%2C1563%2C3183%2C2112&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/dvHkp6FzfIM">Michael Dziedzic / Unsplash</a></span></figcaption></figure><p>Two weeks ago, a <a href="https://arxiv.org/abs/2305.15442">modest-looking paper</a> was uploaded to the arXiv preprint server with the unassuming title “On the invariant subspace problem in Hilbert spaces”. The paper is just 13 pages long and its list of references contains only a single entry.</p>
<p>The paper purports to contain the final piece of a jigsaw puzzle that mathematicians have been picking away at for more than half a century: the <a href="https://en.wikipedia.org/wiki/Invariant_subspace_problem">invariant subspace problem</a>.</p>
<p>Famous open problems often attract ambitious attempts at solutions by interesting characters out to make their name. But such efforts are usually quickly shot down by experts. </p>
<p>However, the author of this short note, Swedish mathematician <a href="https://perenflo.com">Per Enflo</a>, is no ambitious up-and-comer. He is almost 80, has made a name for himself solving open problems, and has quite a history with the problem at hand.</p>
<h2>Per Enflo: mathematics, music, and a live goose</h2>
<p>Born in 1944 and now an emeritus professor at Kent State University, Ohio, Enflo has had a remarkable career, not only in mathematics but also in music. </p>
<p>He is a renowned concert pianist who has performed and recorded numerous piano concertos, and has performed solo and with orchestras across the world.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/530501/original/file-20230607-27-i573ii.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A serious looking older man is handing a goose in a basket to a cheerful younger man." src="https://images.theconversation.com/files/530501/original/file-20230607-27-i573ii.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/530501/original/file-20230607-27-i573ii.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=662&fit=crop&dpr=1 600w, https://images.theconversation.com/files/530501/original/file-20230607-27-i573ii.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=662&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/530501/original/file-20230607-27-i573ii.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=662&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/530501/original/file-20230607-27-i573ii.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=832&fit=crop&dpr=1 754w, https://images.theconversation.com/files/530501/original/file-20230607-27-i573ii.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=832&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/530501/original/file-20230607-27-i573ii.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=832&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Polish mathematician Stanislaw Mazur (left) promised a live goose to anyone who solved a particularly difficult problem. In 1972, Per Enflo collected the prize.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Per_Enflo#/media/File:MazurGes.jpg">Wikimedia</a></span>
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</figure>
<p>Enflo is also one of the great problem-solvers in a field called functional analysis. Aside from his work on the invariant subspace problem, Enflo solved two other major problems – the basis problem and the approximation problem – both of which had remained open for more than 40 years. </p>
<p>By solving the approximation problem, Enflo cracked an equivalent puzzle called Mazur’s goose problem. Polish mathematician Stanisław Mazur had in 1936 promised a live goose to anyone who solved his problem – and in 1972 he kept his word, presenting the goose to Enflo.</p>
<h2>What’s an invariant subspace?</h2>
<p>Now we know the main character. But what about the invariant subspace problem itself?</p>
<p>If you’ve ever taken a first-year university course in linear algebra, you will have come across things called vectors, matrices and eigenvectors. If you haven’t, we can think of a vector as an arrow with a length and a direction, living in a particular vector space. (There are lots of different vector spaces with different numbers of dimensions and various rules.) </p>
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<p>
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<strong>
Read more:
<a href="https://theconversation.com/explainer-the-point-of-pure-mathematics-2385">Explainer: the point of pure mathematics</a>
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</p>
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<p>A matrix is something that can transform a vector, by changing the direction and/or length of the line. If a particular matrix <em>only</em> transforms the length of a particular vector (meaning the direction is either the same or flipped in the opposite direction), we call the vector an eigenvector of the matrix.</p>
<p>Another way to think about this is to say that the matrix transforms the eigenvectors (and any lines parallel to them) back onto themselves: these lines are invariant for this matrix. Taken together, we call these lines <em>invariant subspaces</em> of the matrix.</p>
<p>Eigenvectors and invariant subspaces are also of interest beyond just mathematics – to take one example, it has been said that Google owes its success to “<a href="https://www.rose-hulman.edu/%7Ebryan/googleFinalVersionFixed.pdf">the $25 billion eigenvector</a>”. </p>
<h2>What about spaces with an infinite number of dimensions?</h2>
<p>So that’s an invariant subspace. The invariant subspace problem is a little more complicated: it is about spaces with an <em>infinite number of dimensions</em>, and it asks whether every linear operator (the equivalent of a matrix) in those spaces must have an invariant subspace.</p>
<p>More precisely (hold onto your hat): the invariant subspace problem asks whether every bounded linear operator <em>T</em> on a complex Banach space <em>X</em> admits a non-trivial invariant subspace <em>M</em> of <em>X</em>, in the sense that there is a subspace <em>M</em> ≠ {0}, <em>X</em> of <em>X</em> such that <em>T</em>(<em>M</em>) is contained back in <em>M</em>. </p>
<p>Stated in this way, the invariant subspace problem was posed during the middle of last century, and eluded all attempts at a solution. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/pythagoras-revenge-humans-didnt-invent-mathematics-its-what-the-world-is-made-of-172034">Pythagoras’ revenge: humans didn’t invent mathematics, it’s what the world is made of</a>
</strong>
</em>
</p>
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<p>But as is often the case when mathematicians can’t solve a problem, we move the goalposts. Mathematicians working on this problem narrowed their focus by restricting the problem to particular classes of spaces and operators. </p>
<p>The first breakthrough was made by Enflo in the 1970s (although his result was not <a href="https://link.springer.com/article/10.1007/BF02392260">published</a> until 1987). He answered the problem in the negative, by constructing an operator on a Banach space <em>without</em> a non-trivial invariant subspace.</p>
<h2>What’s new about this new proposed solution?</h2>
<p>So what is the current status of the invariant subspace problem? If Enflo solved it in 1987, why has he solved it again?</p>
<p>Well, Enflo settled the problem for Banach spaces in general. However, there is a particularly important kind of Banach space called a Hilbert space, which has a strong sense of geometry and is widely used in physics, economics and applied mathematics.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1662248421649006593"}"></div></p>
<p>Resolving the invariant subspace problem for operators on Hilbert spaces has been stubbornly difficult, and it is this which Enflo claims to have achieved.</p>
<p>This time Enflo answers in the affirmative: his paper argues that every bounded linear operator on a Hilbert space does have an invariant subspace.</p>
<h2>Expert review is still to come</h2>
<p>I have not worked through Enflo’s preprint line by line. Enflo himself is <a href="https://www.ucm.es/imi/boletin00091#noticia">reportedly cautious</a> about the solution, as it has not yet been reviewed by experts.</p>
<p>Peer review of Enflo’s earlier proof, for Banach spaces in general, took <a href="https://link.springer.com/article/10.1007/s00032-005-0048-7">several years</a>. However, that paper ran to more than 100 pages, so a review of the 13 pages of the new paper should be much speedier. </p>
<p>If correct, it will be a remarkable achievement, especially for someone who has already produced so many remarkable achievements over such a large span of time. Enflo’s many contributions to mathematics, and his answers to many open problems, have made a big impact on the field, generating new techniques and ideas. </p>
<p>I’m looking forward to finding out whether Enflo’s work now closes the book on the invariant subspace problem, and to seeing the new mathematics that may emerge out of its conclusion.</p><img src="https://counter.theconversation.com/content/206859/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nathan Brownlowe 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>Swedish mathematician Per Enflo famously received a live goose for settling a difficult unsolved problem. Has he done it again?Nathan Brownlowe, Senior Lecturer in the School of Mathematics and Statistics, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1956972023-03-17T12:30:17Z2023-03-17T12:30:17ZThose seeds clinging to your hiking socks may be from invasive plants – here’s how to avoid spreading them to new locations<figure><img src="https://images.theconversation.com/files/514780/original/file-20230311-3629-ak0c82.jpg?ixlib=rb-1.1.0&rect=0%2C3%2C2048%2C1529&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">These stowaways can do a lot of damage.</span> <span class="attribution"><a class="source" href="https://flic.kr/p/8sGFmW">Brett L./ Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>With spring settling in across the U.S. and days lengthening, many people are ready to spend more time outside. But after a walk outdoors, have you ever found seeds clinging to your clothes? Lodged in your socks and shoelaces? Perhaps tangled in your pet’s fur? While most of us don’t give these hitchhikers much thought, seeds and burrs may be the first signs of invasive plant spread. </p>
<p>Certain species of non-native invasive plants produce seeds designed to attach to unsuspecting animals or people. Once affixed, these sticky seeds can be carried long distances before they fall off in new environments. With favorable conditions, they can become established quickly and outcompete native plants.</p>
<p>Outdoor recreation has <a href="https://outdoorindustry.org/resource/2022-outdoor-participation-trends-report/#">expanded at a record pace</a> across the U.S. in recent years. Overcrowding in outdoor spaces <a href="https://thetrek.co/examining-impact-overcrowding-hiking-trails/">has many harmful effects</a>, from <a href="https://doi.org/10.1016/S0169-2046(02)00202-5">degrading trails</a> to accelerating the introduction and spread of invasive plants. </p>
<p>As a <a href="https://scholar.google.com/citations?user=nmAblPEAAAAJ&hl=en&oi=ao">recreation ecologist</a> and an avid hiker, I study how people inadvertently spread invasive plants along trails. There are simple things that everyone can do before, during and after going outdoors to avoid picking up plant hitchhikers and help maintain trail systems for others to enjoy. </p>
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<figcaption><span class="caption">Like many states, Iowa is battling dozens of invasive plants.</span></figcaption>
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<h2>Hardy, numerous and adaptable</h2>
<p>Invasive plants are non-native species that can harm <a href="http://dx.doi.org/10.1016/j.ecolind.2019.106020">the environment, human health and the economy</a> when they are introduced into new areas. However, not all non-native plants are invasive. </p>
<p>Plants with invasive capabilities tend to grow quickly, adapt easily to many different environmental conditions, produce seeds in vast quantities and successfully disperse and germinate them. These characteristics enable the plants to spread efficiently to different areas. Many vectors <a href="https://doi.org/10.3897/natureconservation.24.20607">help invasive plants disperse</a>, including birds, animals, wind, water and humans, via clothing, shoes, pets, gear and vehicles.</p>
<p>Invasive plant seeds tend to be small in size, high in number and hardy. They can persist in soil for many years, remaining viable and ready to germinate when conditions are right.</p>
<p>These seeds will usually germinate earlier in spring than those of native plants and keep their leaves until late fall, crowding out and outcompeting native varieties. Each species produces seeds on a particular schedule – annual, biennial or perennial – and at a specific time. For example, invasive biennial <a href="https://doi.org/10.1890/08-0845.1">garlic mustard</a> releases seeds every two years in late spring. </p>
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<h2>No cheap solutions</h2>
<p>Invasive plants have many harmful ecological impacts. One of the <a href="https://doi.org/10.1080/07352680490505150">most familiar U.S. examples is kudzu</a>, a climbing vine that has smothered trees across the Southeast. </p>
<p>Kudzu grows prolifically, outcompeting native vegetation. It also <a href="https://doi.org/10.1890/ES13-00142.1">alters the nitrogen cycle</a> by increasing soil nitrogen levels and releasing nitric oxide, a gas that reduces air quality and promotes ground-level ozone pollution.</p>
<p>In the western U.S., carpets of <a href="https://theconversation.com/invasive-grasses-are-fueling-wildfires-across-the-us-126574">invasive grasses</a>, such as <a href="https://doi.org/10.1007/s10530-017-1641-8">cheatgrass</a> and <a href="https://www.invasivespeciesinfo.gov/terrestrial/plants/medusahead">medusahead</a>, create highly flammable fine fuels. Their presence makes wildfires more frequent and intense. </p>
<p>Some invasive plants directly threaten human health. <a href="https://www.invasivespeciescentre.ca/invasive-species/meet-the-species/invasive-plants/giant-hogweed/">Giant hogweed</a> is an herb in the carrot family that can grow 15 to 20 feet tall. Its poisonous sap can cause <a href="https://www.fws.gov/story/dont-touch-these-plants">severe skin burns</a>. Others, such as poison hemlock and water hemlock, are highly toxic to humans and animals if consumed.</p>
<p>Managing invasive plants, animals and insects is a growing problem, with costs that <a href="https://doi.org/10.1038/s41586-021-03405-6">run into billions of dollars annually</a>. A 2022 study estimated the annual cost of managing biological invasions in the U.S. at <a href="https://doi.org/10.1016/j.scitotenv.2021.151318">about US$21 billion</a> as of 2020.</p>
<p>Invasives are especially threatening for remote, biodiversity-rich places like <a href="https://doi.org/10.1080/17550874.2022.2144777">Antarctica</a>, where remoteness and geographic isolation <a href="https://www.pnas.org/doi/10.1073/pnas.1804179115">promote endemic species</a> – those only found in a particular geographic region. These endemics evolve in the absence of natural competitors and predators, so introducing invasives can have catastrophic consequences. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/514784/original/file-20230311-3915-eiamcv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A hiker's feet, with muddy gaiters zipped over shoes." src="https://images.theconversation.com/files/514784/original/file-20230311-3915-eiamcv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/514784/original/file-20230311-3915-eiamcv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=467&fit=crop&dpr=1 600w, https://images.theconversation.com/files/514784/original/file-20230311-3915-eiamcv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=467&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/514784/original/file-20230311-3915-eiamcv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=467&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/514784/original/file-20230311-3915-eiamcv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=587&fit=crop&dpr=1 754w, https://images.theconversation.com/files/514784/original/file-20230311-3915-eiamcv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=587&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/514784/original/file-20230311-3915-eiamcv.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">Fastening gaiters over hiking shoes is an effective way to keep invasive seeds from attaching.</span>
<span class="attribution"><span class="source">Megan Dolman</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<h2>Recreational trails act as corridors</h2>
<p>Many invasive plants thrive on disturbed soil. Decades of research has shown that recreational trails promote the introduction of invasive plant species into natural and protected areas, including <a href="https://doi.org/10.1002/eap.2239">national parks</a> and national scenic trails like the <a href="https://www.nps.gov/appa/index.htm">Appalachian Trail</a>.</p>
<p>The Appalachian Trail is the longest hiking-only footpath in the world, extending almost 2,200 miles from Georgia to Maine. <a href="https://appalachiantrail.org/our-work/about-us/media-room/">More than 3 million visitors</a> hike on some portion of it every year. Invasive plants <a href="https://appalachiantrail.org/official-blog/five-common-invasive-species-along-at/">commonly found along the trail</a> include garlic mustard, multiflora rose and purple loosestrife. </p>
<p>In a recent study, I worked with the U.S. Geological Survey to investigate Appalachian Trail hikers’ <a href="https://doi.org/10.1016/j.jort.2022.100581">invasive plant knowledge, perceptions, and behaviors</a>. We found that most hikers were unaware of this issue. As a result, few took precautions to avoid contributing to it.</p>
<p>Here are things that concerned hikers can do to help manage invasive plants:</p>
<p>– <a href="https://www.invasivespeciesinfo.gov/species-type">Identify</a> and <a href="https://www.invasivespeciesinfo.gov/subject/reporting">report</a> sightings of invasive plants. The more land managers know about where these species are present, the more effectively they can monitor and manage their spread. </p>
<p>– <a href="https://www.invasivespeciesinfo.gov/type/smartphone-applications">Smartphone apps</a>, like Early Detection & Distribution Mapping System <a href="https://www.eddmaps.org/">EDDMapS</a>, <a href="https://www.inaturalist.org/">iNaturalist</a> and <a href="https://wildspotter.org/">Wild Spotter</a>, make this task easier. Or you can <a href="https://www.invasive.org/report.cfm">search and report by state</a>. Simply take a picture and identify and report when and where you see invasives. </p>
<p>– Arrive with clean gear. Cleaning shoes, clothing and equipment before and after going outdoors is one of the most effective ways to minimize invasive plant introduction and spread. The <a href="https://naisma.org/">North American Invasive Species Management Association</a>’s <a href="https://playcleango.org/">PlayCleanGo</a> campaign has installed <a href="https://playcleango.org/2021/08/12/boot-brush-stations-are-they-effective/">boot brush stations at trailheads</a> to remove <a href="https://doi.org/10.1080/14486563.2020.1838352">seeds lodged in boot treads</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/514782/original/file-20230311-3415-t58ci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A sign above a metal brush directs hikers to clean their boots." src="https://images.theconversation.com/files/514782/original/file-20230311-3415-t58ci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/514782/original/file-20230311-3415-t58ci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/514782/original/file-20230311-3415-t58ci.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/514782/original/file-20230311-3415-t58ci.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/514782/original/file-20230311-3415-t58ci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/514782/original/file-20230311-3415-t58ci.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/514782/original/file-20230311-3415-t58ci.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&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 boot cleaning station at a Hawaii trailhead.</span>
<span class="attribution"><span class="source">Megan Dolman</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>– Choose clothing and shoes carefully. Certain surfaces, such as uncovered socks, shoelaces, fleece and Velcro, are <a href="https://doi.org/10.1016/j.jenvman.2009.08.002">more seed-friendly</a> than smoother materials such as nylon. Wearing pants that are uncuffed and pocketless to minimize snag points and fastening gaiters over shoes are easy ways to repel plant hitchhikers. Gaiters will also keep pebbles and mud out of your boots.</p>
<p>– Follow the <a href="https://lnt.org/why/7-principles/">Leave No Trace principles</a>, which outline minimum-impact strategies for visiting the outdoors. For example, stick to marked formal trails to avoid dispersing invasive plants off-trail. Camp on designated or well-established campsites, and don’t transport firewood between sites – use certified or local firewood and hay. Clean your pets and vehicles as well as your clothes before and after hitting the trail. </p>
<p>People who want to do more to protect the outdoors can take a <a href="https://lnt.org/courses/online_awareness_take_action_html5/#/">free Leave No Trace online course</a> and take the <a href="https://playcleango.org/take-action/take-pledge/">PlayCleanGo Pledge</a> to make a difference with their actions.</p><img src="https://counter.theconversation.com/content/195697/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Megan Dolman has received travel funding from the School of Geography and the Environment and Brasenose College, University of Oxford. </span></em></p>Invasive species cause billions of dollars in damage across the US every year. Hikers and backpackers can take simple steps to avoid spreading seeds and making the problem worse.Megan Dolman, PhD candidate in Ecology, Evolution and Behavior, Boise State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1396452020-06-25T12:35:23Z2020-06-25T12:35:23ZHow deforestation helps deadly viruses jump from animals to humans<figure><img src="https://images.theconversation.com/files/343503/original/file-20200623-188911-16eqf9f.jpg?ixlib=rb-1.1.0&rect=0%2C10%2C3104%2C2134&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Pangolins have been found with covonaviruses that are genetically similar to the one afflicting humans today.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/zimbabwe-game-reserve-guide-matius-mhambe-holds-marimba-a-news-photo/610214710">Jekesai Njikizana/AFP/Getty Images</a></span></figcaption></figure><p>The coronavirus pandemic, suspected of originating in bats and pangolins, has brought the risk of viruses that jump from wildlife to humans into stark focus.</p>
<p>These leaps often happen at the edges of the world’s tropical forests, where deforestation is increasingly bringing people into contact with animals’ natural habitats. Yellow fever, malaria, Venezuelan equine encephalitis, Ebola – all of these pathogens have spilled over from one species to another at the margins of forests.</p>
<p>As <a href="https://id.medicine.ufl.edu/profile/vittor-amy/">doctors</a> and <a href="http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4167488J6">biologists</a> <a href="http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4727511E6&idiomaExibicao=2">specializing in infectious diseases</a>, we have studied these and other zoonoses as they spread in Africa, Asia and the Americas. We found that <a href="http://doi.org/10.1098/rstb.2016.0125">deforestation has been a common theme</a>.</p>
<p>More than half of the world’s tropical deforestation is driven by four commodities: beef, soy, palm oil and wood products. They replace mature, biodiverse tropical forests with monocrop fields and pastures. As the forest is degraded piecemeal, animals still living in isolated fragments of natural vegetation struggle to exist. When human settlements encroach on these forests, human-wildlife contact can increase, and new opportunistic animals may also migrate in.</p>
<p>The resulting disease spread shows the interconnectedness of natural habitats, the animals that dwell within it, and humans.</p>
<h2>Yellow fever: Monkeys, humans and hungry mosquitoes</h2>
<p>Yellow fever, a viral infection transmitted by mosquitoes, famously halted progress on the Panama Canal in the 1900s and shaped the history of Atlantic coast cities from Philadelphia to Rio de Janeiro. Although a yellow fever vaccine has been available since the 1930s, the disease continues to afflict 200,000 people a year, a third of whom die, mostly in West Africa. </p>
<p>The virus that causes it lives in primates and is spread by mosquitoes that tend to dwell high in the canopy where these primates live.</p>
<p>In the early 1990s, a yellow fever outbreak was <a href="http://doi.org/10.4269/ajtmh.1998.59.644">reported for the first time in the Kerio Valley in Kenya</a>, where deforestation had fragmented the forest. Between 2016 and 2018, <a href="https://www.who.int/csr/don/09-march-2018-yellow-fever-brazil/en/">South America saw its largest number of yellow fever cases in decades</a>, resulting in around 2,000 cases, and hundreds of deaths. The impact was severe in the extremely vulnerable Atlantic forest of Brazil – a biodiversity hotspot that has <a href="https://www.ioes.ucla.edu/wp-content/uploads/Giorgi-F07-fieldreport-FIN.pdf">shrunk to 7%</a> of its original forest cover. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/343340/original/file-20200622-55017-1f4z10r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/343340/original/file-20200622-55017-1f4z10r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/343340/original/file-20200622-55017-1f4z10r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/343340/original/file-20200622-55017-1f4z10r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/343340/original/file-20200622-55017-1f4z10r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/343340/original/file-20200622-55017-1f4z10r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/343340/original/file-20200622-55017-1f4z10r.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">Veterinarians inspect monkeys found dead in Brazil, where primates are suspected of spreading yellow fever.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/veterinarians-examine-dead-monkeys-at-the-municipal-news-photo/916257726">Carl de Souza/AFP via Getty Images</a></span>
</figcaption>
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<p>Shrinking habitat has been <a href="https://doi.org/10.1002/ajp.23089">shown to concentrate howler monkeys</a> – one of the main South American yellow fever hosts. A study on primate density in Kenya further demonstrated that forest fragmentation led a greater density of primates, which in turn <a href="http://doi.org/10.1111/j.1365-2656.2008.01481.x">led to pathogens becoming more prevalent</a>. </p>
<p>Deforestation resulted in patches of forest that both concentrated the primate hosts and favored the mosquitoes that could transmit the virus to humans. </p>
<h2>Malaria: Humans can also infect wildlife</h2>
<p>Just as wildlife pathogens can jump to humans, humans can cross-infect wildlife. </p>
<p>Falciparum malaria kills hundreds of thousands of people yearly, especially in Africa. But in the Atlantic tropical forest of Brazil, we have also found a surprisingly high rate of <em>Plasmodium falciparum</em> (the malaria parasite responsible for severe malaria) circulating <a href="http://doi.org/10.1186/s12936-015-0680-9">in the absence of humans</a>. That raises the possibility that this parasite may be infecting <a href="http://www.nhc.ed.ac.uk/index.php?page=493.166.504.508.511">new world monkeys</a>. Elsewhere in the Amazon, monkey species have <a href="http://doi.org/10.1186/1475-2875-12-180">become naturally infected</a>. In both cases, deforestation could have facilitated cross-infection.</p>
<p>We and other scientists have extensively documented the <a href="https://doi.org/10.4269/ajtmh.2006.74.3">associations between deforestation</a> <a href="http://doi.org/10.1073/pnas.1905315116">and malaria</a> <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3757555/">in the Amazon</a>, showing how the malaria-carrying mosquitoes and human malaria cases are <a href="http://doi.org/10.1371/journal.pone.0085725">strongly linked</a> <a href="http://doi.org/10.1590/0074-02760170522">to deforested habitat</a>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/343339/original/file-20200622-54981-ass960.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/343339/original/file-20200622-54981-ass960.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/343339/original/file-20200622-54981-ass960.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/343339/original/file-20200622-54981-ass960.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/343339/original/file-20200622-54981-ass960.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/343339/original/file-20200622-54981-ass960.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/343339/original/file-20200622-54981-ass960.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Children in Ethiopia read under mosquito netting, used to protect people from mosquitoes that transmit malaria.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/in-ambowuha-birtukan-demissie-reads-to-her-siblings-before-news-photo/585855656?adppopup=true">Louise Gubb/Corbis via Getty Images</a></span>
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<p>Another type of malaria, <em>Plasmodium knowlesi</em>, known to circulate among monkeys, <a href="https://doi.org/10.1016/S0140-6736(04)15836-4">became a concern to human health</a> over a decade ago in Southeast Asia. Several studies have shown that areas sustaining higher rates of forest loss also had <a href="http://doi.org/10.3201/eid2202.150656">higher rates of human infections</a>, and that the mosquito vectors and monkey hosts spanned a wide range of habitats <a href="http://doi.org/10.1186/s13071-016-1527-0">including disturbed forest</a>.</p>
<h2>Venezuelan equine encephalitis: Rodents move in</h2>
<p>Venezuelan equine encephalitis is another mosquito-borne virus that is estimated to cause tens to hundreds of thousands of humans to develop febrile illnesses every year. Severe infections can lead to encephalitis and even death. </p>
<p>In the Darien province of Panama, we found that two rodent species had particularly high rates of infection with Venezuelan equine encephalitis virus, leading us to suspect that <a href="https://doi.org/10.1371/journal.pntd.0004554">these species may be the wildlife hosts</a>. </p>
<p>One of the species, Tome’s spiny rat, has also been <a href="http://doi.org/10.3201/eid1105.041251">implicated in other studies</a>. The other, the short-tailed cane mouse, is also involved in the transmission of zoonotic diseases such as hantavirus and possibly Madariaga virus, an emergent encephalitis virus. </p>
<p>While <a href="http://doi.org/10.1017/S0266467498000509">Tome’s spiny rat</a> is widely found in tropical forests in the Americas, it <a href="https://doi.org/10.1644/1545-1542(2000)081%3C0070:MUBATF%3E2.0.CO;2">readily occupies regrowth and forest fragments</a>. The <a href="https://animaldiversity.org/accounts/Zygodontomys_brevicauda/">short-tailed cane mouse</a> prefers habitat on the edge of forests and abutting cattle pastures. </p>
<p>As deforestation in this region progresses, these two rodents can occupy forest fragments, cattle pastures and the regrowth that arises when fields lie fallow. <a href="http://doi.org/10.1038/s41598-017-07476-2">Mosquitoes also occupy these areas</a> and can bring the virus to humans and livestock.</p>
<h2>Ebola: Disease at the forest’s edge</h2>
<p>Vector-borne diseases are not the only zoonoses sensitive to deforestation. Ebola was first described in 1976, but outbreaks have become more common. The <a href="https://www.cdc.gov/vhf/ebola/history/2014-2016-outbreak/index.html">2014-2016 outbreak</a> killed more than 11,000 people in West Africa and drew attention to diseases that can spread from wildlife to humans. </p>
<p>The natural transmission cycle of the Ebola virus remains elusive. Bats have been implicated, with possible additional ground-dwelling animals maintaining “silent” transmission between human outbreaks. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/343343/original/file-20200622-54985-143xodx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/343343/original/file-20200622-54985-143xodx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=394&fit=crop&dpr=1 600w, https://images.theconversation.com/files/343343/original/file-20200622-54985-143xodx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=394&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/343343/original/file-20200622-54985-143xodx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=394&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/343343/original/file-20200622-54985-143xodx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=496&fit=crop&dpr=1 754w, https://images.theconversation.com/files/343343/original/file-20200622-54985-143xodx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=496&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/343343/original/file-20200622-54985-143xodx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=496&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Bats, sometimes eaten as food, have been suspected of spreading Ebola.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/ugandan-man-displays-a-bat-he-captured-for-food-december-1-news-photo/1320445">Tyler Hicks/Getty Images</a></span>
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<p>While the exact nature of transmission is not yet known, several studies have shown that deforestation and forest fragmentation were <a href="https://doi.org/10.1038/s41598-017-14727-9">associated with outbreaks</a> <a href="https://doi.org/10.1038/srep41613">between 2004 and 2014</a>. In addition to possibly concentrating Ebola wildlife hosts, fragmentation may serve as a <a href="http://doi.org/10.1590/0074-0276140417">corridor for pathogen-carrying animals</a> to spread the virus over large areas, and it may increase human contact with these animals along the forest edge.</p>
<h2>What about the coronavirus?</h2>
<p>While the origin of the SARS-CoV-2 outbreak hasn’t been proved, a <a href="https://doi.org/10.1038/s41591-020-0820-9">genetically similar virus</a> has been detected in <a href="http://doi.org/10.1016/j.cub.2020.03.022">intermediate horseshoe bats and</a> <a href="https://doi.org/10.1038/s41586-020-2169-0">Sunda pangolins</a>.</p>
<p>The range of the Sunda pangolin – which is critically endangered – overlaps with the <a href="https://doi.org/10.1046/j.1365-2699.2000.00381.x">intermediate horseshoe bat</a> in the forests of Southeast Asia, where it lives in mature tree hollows. As forest habitat shrinks, could pangolins also experience increased density and susceptibility to pathogens? </p>
<p>In fact, in small <a href="https://doi.org/10.1002/ece3.4632">urban forest fragments</a> in Malaysia, the Sunda pangolin was detected even though overall mammal diversity was much lower than a comparison tract of contiguous forest. This shows that this animal is able to persist in fragmented forests where it could increase contact with humans or other animals that can harbor potentially zoonotic viruses, such as bats. The Sunda pangolin is poached for its meat, skin and scales and imported illegally from Malaysia and Vietnam into China. A wet market in Wuhan that sells such animals has been <a href="https://doi.org/10.1016/j.meegid.2020.104384">suspected as a source</a> of the current pandemic.</p>
<h2>Preventing zoonotic spillover</h2>
<p>There is still a lot that we don’t know about how viruses jump from wildlife to humans and what might drive that contact. </p>
<p>Forest fragments and their associated landscapes encompassing forest edge, agricultural fields and pastures have been a repeated theme in tropical zoonoses. While many species disappear as forests are cleared, others have been able to adapt. Those that adapt may become more concentrated, increasing the rate of infections. </p>
<p>Given the evidence, it is clear humans need to balance the production of food, forest commodities and other goods with the protection of tropical forests. Conservation of wildlife may keep their pathogens in check, preventing zoonotic spillover, and ultimately benefiting humans, too.</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/139645/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Amy Y. Vittor receives funding from the National Institutes of Health. She is affiliated with the group Florida Clinicians for Climate Action as a steering committee member. </span></em></p><p class="fine-print"><em><span>Gabriel Zorello Laporta receives funding from the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq
grant n. 307432/2019-0) and received funding from the São Paulo Research Foundation (FAPESP grant n. 2014/09774-1). </span></em></p><p class="fine-print"><em><span>Maria Anice Mureb Sallum receives funding from Fundação de Amparo à Pesquisa do Estado de São Paulo, FAPESP # 2014/26229-7, and Conselho Nacional de Pesquisa, CNPq # 301877/2016-5. </span></em></p>Yellow fever, malaria and Ebola all spilled over from animals to humans at the edges of tropical forests. The new coronavirus is the latest zoonosis.Amy Y. Vittor, Assistant Professor of Medicine, University of FloridaGabriel Zorello Laporta, Professor of biology and infectious diseases, Faculdade de Medicina do ABCMaria Anice Mureb Sallum, Professor of Epidemiology, Universidade de São Paulo (USP)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1202832019-07-17T19:46:32Z2019-07-17T19:46:32ZAir travel spreads infections globally, but health advice from inflight magazines can limit that<figure><img src="https://images.theconversation.com/files/284420/original/file-20190717-173370-3btbfw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Our research showed that inflight magazines offered travellers health advice on everything from dehydration to swollen ankles, but hardly anything on avoiding catching and spreading infectious diseases.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/asian-passenger-reading-magazine-menue-catalog-1155462985?src=vUDfEziJwFDV7GZr5OYMRA-1-0&studio=1">from www.shutterstock.com</a></span></figcaption></figure><p>“Travel safe, travel far, travel wide, and travel often,” <a href="https://thoughtcatalog.com/matthew-kepnes/2014/01/53-travel-quotes-to-inspire-you-to-see-the-world/">says</a> <a href="https://www.nomadicmatt.com/">Nomadic Matt</a>, the American who quit his job to travel the world, write about it and coach others to do the same.</p>
<p>But there’s a downside to all this travel, with its unprecedented volume of passengers moving from one side of the world to the other, largely by plane.</p>
<p>There’s the risk of those passengers spreading infectious diseases and microorganisms resistant to multiple drugs (superbugs) around the world.</p>
<p>Yet, our recently published <a href="https://www.sciencedirect.com/science/article/pii/S1477893919301218">research</a> into health advice provided by inflight magazines shows plane passengers are given practically no advice on how to limit the spread of infectious diseases.</p>
<p>Should we be worried about the part air travel plays in spreading infectious diseases? And what can we do about it?</p>
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<strong>
Read more:
<a href="https://theconversation.com/remote-village-to-metropolis-how-globalisation-spreads-infectious-diseases-92216">Remote village to metropolis: how globalisation spreads infectious diseases</a>
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<h2>How big is the risk?</h2>
<p>Low airfares and a series of social and economic factors have made global air travel more common than ever. According to the Australian government department of infrastructure, transport, cities and regional development the <a href="https://www.bitre.gov.au/publications/ongoing/files/International_airline_activity_CY2018.pdf">number of passengers taking international scheduled flights in 2018 was 41.575 million</a>. But the International Air Transport Association projects passenger demand will <a href="https://www.iata.org/pressroom/pr/Pages/2019-02-27-02.aspx">reach 8.2 billion by 2037</a>.</p>
<p>There are many examples of infectious diseases spread via international flying. The World Health Organization documented <a href="https://www.who.int/ith/mode_of_travel/tcd_aircraft/en/">transmission of tuberculosis</a> (TB) on board commercial aircraft during long-haul flights during the 1980s. </p>
<p>Research published in 2011 documents the <a href="https://wwwnc.cdc.gov/eid/article/17/7/10-1135_article">transmission of influenza</a> on two transcontinental international flights in May 2009.</p>
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Read more:
<a href="https://theconversation.com/health-check-are-you-up-to-date-with-your-vaccinations-116510">Health Check: are you up to date with your vaccinations?</a>
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<p>More recently, the current <a href="https://theconversation.com/why-people-born-between-1966-and-1994-are-at-greater-risk-of-measles-and-what-to-do-about-it-110167">global outbreak of measles</a> in many countries, including the Philippines and the United States, gave rise to the risk of transmission during international travel. In a recent case a <a href="https://www.health.nsw.gov.au/Infectious/alerts/Pages/measles-alert-january.aspx">baby</a> too young to be vaccinated who had <a href="https://www.smh.com.au/national/nsw/measles-alert-after-infectious-baby-flew-from-manila-went-to-central-coast-20190603-p51tzs.html">measles</a> returned from Manilla in the Philippines to Sydney, exposing travellers on that flight to infection. </p>
<p>Then there is the risk of transmitting antimicrobial-resistant organisms that cause disease, such as <a href="https://theconversation.com/explainer-what-is-tb-and-am-i-at-risk-of-getting-it-in-australia-75290">multi-drug resistant TB</a>.</p>
<p>Recently, patients in Victoria and New South Wales were identified as carrying the drug-resistant fungus <a href="https://www2.health.vic.gov.au/about/news-and-events/healthalerts/candida-auris-case-detected-in-victoria"><em>Candida auris</em></a>, which they acquired overseas.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-is-candida-auris-and-who-is-at-risk-115293">Explainer: what is Candida auris and who is at risk?</a>
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<p><a href="https://www.ncbi.nlm.nih.gov/pubmed/27890665">One study</a> estimates that over 300 million travellers visit high-risk areas, such as the western Pacific, Southeast Asia and Eastern Mediterranean, each year worldwide, and more than 20% return as new carriers of resistant organisms.</p>
<p>These popular destinations, as well as the Middle East, have high rates of drug resistant organisms.</p>
<h2>How is this happening?</h2>
<p>Aircraft move large volumes of people around the world swiftly. But what sets them apart from buses and trains is that passengers are close together, in confined spaces, for a long time. This increases the risk of transmitting infections.</p>
<p>Passengers interact with high-touch surfaces, such as tray tables, headsets, seats and handles. We cough, sneeze and touch multiple surfaces multiple times during a flight, with limited opportunities to clean our hands with soap and water. </p>
<p>Many infections, such as gastroenteritis and diarrhoea, are spread and contracted by touch and contact.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/flu-lasts-for-more-than-an-hour-in-air-and-on-surfaces-why-cleaning-can-really-help-97823">Flu lasts for more than an hour in air and on surfaces – why cleaning can really help</a>
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</em>
</p>
<hr>
<h2>What can we do about it?</h2>
<p>Providing plane travellers with relevant health advice is one way to limit the spread of infectious diseases via air travel.</p>
<p>This would include information and advice on routine hand washing with soap and water, or using alcohol-based hand rubs, and other basic measures including cough etiquette, such as coughing into your elbow and covering your nose and face.</p>
<p><a href="https://academic.oup.com/jtm/article/4/2/102/1847252">Researchers</a> have looked at the role commercial websites and travel agencies might play in providing that advice. And since the 1990s, airline magazines have been <a href="https://academic.oup.com/jtm/article/4/2/102/1847252">highlighted</a> as an underused source of traveller health advice. More than 20 years on, we discovered little has changed.</p>
<p>In our recent study, published in the journal <a href="https://www.sciencedirect.com/science/article/pii/S1477893919301218">Travel Medicine and Infectious Disease</a>, we looked at the content of inflight magazines from 103 airlines issued during January 2019. </p>
<p>Of the 47 available online, only a quarter (11) included an official section on passengers’ general health and well-being, of which only two contained information related to infection control and the preventing infectious diseases.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/284424/original/file-20190717-173366-w48bmn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/284424/original/file-20190717-173366-w48bmn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/284424/original/file-20190717-173366-w48bmn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/284424/original/file-20190717-173366-w48bmn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/284424/original/file-20190717-173366-w48bmn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/284424/original/file-20190717-173366-w48bmn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/284424/original/file-20190717-173366-w48bmn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/284424/original/file-20190717-173366-w48bmn.jpg?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"></a>
<figcaption>
<span class="caption">Inflight magazines have a potential audience of billions. So why not include advice on hand hygiene and coughing etiquette?</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/1424594042?src=vUDfEziJwFDV7GZr5OYMRA-1-2&studio=1&size=medium_jpg">from www.shutterstock.com</a></span>
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<p>The first magazine, from a UAE-based airline, had an official section on passenger health and well-being that included very limited relevant content. It advised passengers “with blood diseases or ear, nose and sinus infections should seek medical advice before flying”.</p>
<p>There was no further explanation or information, nor were there any strategies to prevent these or other infections.</p>
<p>The second magazine, from a USA-based airline, contained general travel health advice, but none specifically about infectious diseases. </p>
<p>However there was a full-page, colour advertisement next to the health section. This contained images of many disease causing microorganisms on passengers’ tray tables and advocated the use of a disinfectant wipe for hands and other inflight surfaces. </p>
<p>The slogan “because germs are frequent fliers” was displayed across the tray table. This was accompanied by information about the use and effectiveness of disinfectant wipes for hand hygiene and disinfecting surfaces during air travel, public transport use, and in hotels and restaurants.</p>
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Read more:
<a href="https://theconversation.com/going-travelling-dont-forget-insurance-and-to-read-the-fine-print-107961">Going travelling? Don't forget insurance (and to read the fine print)</a>
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<p>Inflight magazines are valuable assets for airlines and are the source of considerable advertising revenue. They are read by potentially billions of passengers every year. The results of this study show that they are a greatly underused source of information about infection control and measures to prevent the spread of infectious diseases. </p>
<p>Airlines should also provide health advice to passengers in other media, in particular video screens, about infection prevention and basic control measures such as hand hygiene, cough etiquette and personal hygiene. </p>
<p>Such advice should be provided before, during and after the flight. It could also include destination-related advice for particularly risky travel routes and destinations.</p>
<h2>More information for passengers</h2>
<p>Airlines providing health advice to passengers is just one way to limit the spread of infectious diseases and antimicrobial-resistant organisms around the world via air travel.</p>
<p>This would need to sit alongside other measures, such as <a href="https://wwwnc.cdc.gov/travel/page/travel-industry-information-center">information and guidelines</a> provided to those who travel via the sea.</p>
<p>The simple, low-cost measures highlighted in our research could go a long way to help passengers stay healthy and avoid illness from infectious diseases. At the same time, these measures could reduce the impact of outbreaks of infectious diseases for airlines and society as a whole.</p>
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Read more:
<a href="https://theconversation.com/when-the-drugs-dont-work-how-we-can-turn-the-tide-of-antimicrobial-resistance-71711">When the drugs don’t work: how we can turn the tide of antimicrobial resistance</a>
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<img src="https://counter.theconversation.com/content/120283/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ramon Z. Shaban receives funding from New South Wales Health Pathology and GAMA Healthcare. Ramon Z. Shaban is affiliated with the Marie Bashir Institute for Infectious Diseases and Biosecurity and Susan Wakil School of Nursing and Midwifery within the Faculty of Medicine and Health of the University of Sydney and the Western Sydney Local Health District. He is also Immediate Past President of the Australasian College for Infection Prevention and Control.
</span></em></p><p class="fine-print"><em><span>Cristina Sotomayor-Castillo is affiliated with Marie Bashir Institute for Infectious Disease and Biosecurity and Susan Wakil School of Nursng and Midwifery within the Faculty of Medicine and Health of the University of Sydney and the Western Sydney Local Health District (WSLHD). </span></em></p>Washing hands and coughing into your elbow can help limit the spread of infectious diseases on planes and around the globe. So why don’t passengers read about this in their inflight magazines?Ramon Zenel Shaban, Clinical Chair and Professor of Infection Prevention and Disease Control at the University of Sydney, University of SydneyCristina Sotomayor-Castillo, Senior Research Officer, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1181022019-07-12T12:06:07Z2019-07-12T12:06:07ZTicks spread plenty more for you to worry about beyond Lyme disease<figure><img src="https://images.theconversation.com/files/283715/original/file-20190711-173334-1u1skq3.jpg?ixlib=rb-1.1.0&rect=404%2C134%2C3325%2C2317&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">There's a short window between when a tick bites and when it passes on bacteria or virus.</span> <span class="attribution"><span class="source">MSU Ag Communications, Courtesy Dr. Tina Nations</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>When it comes to problems caused by ticks, Lyme disease hogs a lot of the limelight. But various tick species carry and transmit a collection of other pathogens, some of which cause serious, even fatal, conditions.</p>
<p>In fact, the <a href="https://doi.org/10.1016/j.pt.2012.07.003">number of tick-borne disease cases is on the rise</a> in the United States. The range where various species of ticks live in North America may be <a href="http://dx.doi.org/10.1155/2009/593232">expanding due to climate change</a>. Researchers continue to discover <a href="https://doi.org/10.1128/microbiolspec.EI10-0012-2016">new pathogens that live in ticks</a>. And <a href="https://www.cdc.gov/ticks/longhorned-tick/index.html">new, invasive tick species</a> keep turning up.</p>
<p>In <a href="https://scholar.google.com/citations?user=JVfeckwAAAAJ&hl=en&oi=ao">my career as a</a> <a href="https://doi.org/10.1201/b12686">public health entomologist</a>, I’ve been amazed at the ability of ticks to bounce back from all the ways people try to control them, including with pesticides. Ticks excel at finding new ecological niches for survival. So people and ticks frequently cross paths, exposing us to their bites and the diseases they carry.</p>
<p>Here are some of the lesser-known, but growing, threats from ticks.</p>
<h2>Ticks can spread bacterial diseases</h2>
<p>Certain very small species of bacteria that can cause human diseases, such as rickettsia, ehrlichia and anaplasma, live in ticks. Ticks ingest these bacteria when they drink animals’ blood. Then when the ticks take a subsequent blood meal, they pass the bacteria along to the next animal or person they feed on.</p>
<p>Probably the most well known of these bacterial diseases is <a href="https://www.cdc.gov/rmsf/index.html">Rocky Mountain spotted fever</a>, the most frequently reported rickettsial disease in the U.S., with <a href="https://wonder.cdc.gov/nndss/static/2017/annual/2017-table1.html">about 6,000 cases each year</a>. The number of diagnoses seems to be increasing nationwide, <a href="https://doi.org/10.4269/ajtmh.2009.80.601">especially among Native Americans</a>, probably due to exposure on reservations to free-roaming dogs that can carry ticks.</p>
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<a href="https://images.theconversation.com/files/278758/original/file-20190610-52758-1y6uqpg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/278758/original/file-20190610-52758-1y6uqpg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/278758/original/file-20190610-52758-1y6uqpg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=385&fit=crop&dpr=1 600w, https://images.theconversation.com/files/278758/original/file-20190610-52758-1y6uqpg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=385&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/278758/original/file-20190610-52758-1y6uqpg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=385&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/278758/original/file-20190610-52758-1y6uqpg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=484&fit=crop&dpr=1 754w, https://images.theconversation.com/files/278758/original/file-20190610-52758-1y6uqpg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=484&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/278758/original/file-20190610-52758-1y6uqpg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=484&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">Rocky Mountain spotted fever usually comes with a rash, as on this child.</span>
<span class="attribution"><a class="source" href="https://phil.cdc.gov/Details.aspx?pid=1962">Centers for Disease Control and Prevention, National Center for Immunization and Respiratory Diseases (NCIRD)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>When people get sick with Rocky Mountain spotted fever, they usually come to a clinic with three things: fever, rash and history of tick bite. They may also report severe headache, chills and muscle pains, and gastrointestinal symptoms such as abdominal pain and diarrhea. A skin rash is usually present after a few days, but not always. Mental confusion, coma and death can occur in severe cases. Untreated, the mortality rate is about 20%; and even with treatment, 4% of those infected die.</p>
<p>Not all tick species are effective transmitters of the rickettsia bacteria. Even within the vector species, often <a href="https://doi.org/10.1056/NEJMoa050043">only 1% to 5% of ticks in an area are infected</a>. So getting bitten by a tick that passes rickettsia bacteria on to you is like getting stuck with a needle in a haystack. The primary carriers are the American dog tick in the eastern U.S. and Rocky Mountain wood tick in the West. The brown dog tick has also recently been <a href="http://dx.doi.org/10.15585/mmwr.rr6502a1">shown to be a vector</a>. </p>
<p>In most tick-borne diseases, the <a href="https://jcm.asm.org/content/25/3/557.short">tick needs to feed for some amount of time</a> before any pathogens it’s carrying are transmitted to the animal whose blood it’s eating. Rocky Mountain spotted fever organisms generally take between one and three hours for transmission to occur, so attached ticks need to be removed quickly. Doctors usually prescribe the antibiotic doxycycline to treat Rocky Mountain spotted fever, which works quite well if the disease is recognized early.</p>
<p><iframe id="hCzmS" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/hCzmS/3/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p><a href="https://www.cdc.gov/ehrlichiosis/index.html">Ehrlichiosis</a> is another bacterial disease transmitted from ticks to people. In the U.S. it’s most commonly caused by <em>Ehrlichia chaffeensis</em> bacteria, carried by lone star ticks which are common in the eastern U.S. Ehrlichia bacteria infect a type of blood cell called leukocytes. Human monocytic ehrlichiosis occurs mostly in the southern and south-central U.S.; <a href="https://wonder.cdc.gov/nndss/static/2017/annual/2017-table1.html">1,642 cases were reported</a> to the CDC in 2017. </p>
<p>Ehrlichiosis patients usually have fever, headache, muscle aches and a progressive low white blood cell count. As opposed to Rocky Mountain spotted fever, people get a rash only about 20% to 40% of the time. Doctors usually treat ehrlichiosis with doxycycline.</p>
<p>Another tick-borne bacterial disease to worry about is <a href="http://dx.doi.org/10.15585/mmwr.rr6502a1">human granulocytic anaplasmosis</a>. In human granulocytic anaplasmosis, <em>Anaplasma phagocytophilum</em> bacteria infects a type of white blood cell called granulocytes. It mostly occurs in the upper midwestern and northeastern U.S., and the incidence is increasing, with <a href="https://wonder.cdc.gov/nndss/static/2017/annual/2017-table1.html">5,762 cases of human granulocytic anaplasmosis reported</a> to the CDC in 2017.</p>
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<span class="caption">A female <em>Ixodes scapularis</em> tick.</span>
<span class="attribution"><span class="source">Dr. Blake Layton, MSU</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>Symptoms include fever, headache, muscle aches and progressive low white blood cell count. It’s the deer tick <em>Ixodes scapularis</em> – famously also responsible for Lyme disease – that transmits the Anaplasma bacteria to humans. There’s the unlucky chance that a bite from a deer tick could infect you with both diseases. Again, recommended therapy is doxycycline.</p>
<h2>Ticks can carry viruses, too</h2>
<p>People usually think of mosquitoes when they think of insect-transmitted viruses – dengue, Zika or West Nile garner a lot of headlines. But ticks can transmit viruses, too.</p>
<p>Scientists have historically grouped tick-borne viral diseases into two categories. One is diseases similar to dengue fever. The main dengue-like viral disease transmitted by ticks in the U.S. is <a href="https://www.ncbi.nlm.nih.gov/pubmed/19954">Colorado tick fever</a>, which occurs in mountainous areas of the West.</p>
<p>The other group of tick-borne diseases resemble mosquito-borne encephalitis. Most of these illnesses, characterized by brain inflammation, are not found in the U.S. <a href="https://doi.org/10.1146/annurev-ento-112408-085446">Powassan encephalitis is the one that is</a>, occurring in the northeastern U.S. and adjacent regions of Canada.</p>
<p>Powassan is a relatively rare but serious human disease, characterized by sudden onset of fever with temperature up to 104 degrees Fahrenheit, along with convulsions. Brain inflammation is usually severe, with vomiting, respiratory distress and prolonged fever.</p>
<p><a href="https://wonder.cdc.gov/nndss/static/2017/annual/2017-table1.html">Fewer than 100 cases of Powassan have been reported</a> in North America, with about half of them fatal. Its incidence seems to be increasing; there were 34 cases of Powassan reported during 2017. POW is maintained in a natural cycle when ticks – primarily <em>Ixodes cookei</em> – infect animals with the virus via their bites. Then these infected animals may serve as what scientists call <a href="https://en.wikipedia.org/wiki/Natural_reservoir">disease reservoirs</a>, infecting new ticks when they feed on their blood.</p>
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<a href="https://images.theconversation.com/files/283723/original/file-20190711-173347-19l9cwa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/283723/original/file-20190711-173347-19l9cwa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/283723/original/file-20190711-173347-19l9cwa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=412&fit=crop&dpr=1 600w, https://images.theconversation.com/files/283723/original/file-20190711-173347-19l9cwa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=412&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/283723/original/file-20190711-173347-19l9cwa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=412&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/283723/original/file-20190711-173347-19l9cwa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=517&fit=crop&dpr=1 754w, https://images.theconversation.com/files/283723/original/file-20190711-173347-19l9cwa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=517&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/283723/original/file-20190711-173347-19l9cwa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=517&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">Tiny larval lone star ticks next to a penny.</span>
<span class="attribution"><span class="source">Jerome Goddard</span></span>
</figcaption>
</figure>
<p>In the last decade, researchers have found additional new tick-borne viruses in the U.S. About <a href="https://europepmc.org/articles/pmc5779346">30 cases of Heartland virus</a> have thus far been identified. It’s associated with the lone star tick and has been recognized in Missouri, Oklahoma, Kentucky and Tennessee.</p>
<p>A few cases of a new Thogotovirus <a href="https://doi.org/10.3201/eid2312.170532">called Bourbon virus</a> have been identified in the Midwest and southern U.S. The lone star tick may be the vector of Bourbon virus as well.</p>
<h2>A food allergy triggered by a tick bite</h2>
<p>Maybe the most bizarre threat from ticks is the “<a href="https://doi.org/10.1097/ACI.0b013e3283624560">red meat allergy</a>” scientists have recently traced back to tick bites. People can become allergic to eating meat when a tick’s saliva passes on the carbohydrate galactose-α-1.3-galactose it had previously picked up in a blood meal from an animal. If prone to allergies, the person can get sensitized to that alpha-gal molecule that’s found in animal blood and other tissues.</p>
<p>Then days or weeks later, he or she may develop hives, swollen skin and lips, or even life-threatening anaphylactic shock three to six hours after eating red meat. Meats containing alpha-gal include beef, pork, lamb, squirrel, rabbit, horse, goat, deer, kangaroo, seal and whale. People who become sensitized to alpha-gal may still eat chicken, turkey and fish.</p>
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<a href="https://images.theconversation.com/files/283738/original/file-20190711-173347-3jgt7f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/283738/original/file-20190711-173347-3jgt7f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/283738/original/file-20190711-173347-3jgt7f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/283738/original/file-20190711-173347-3jgt7f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/283738/original/file-20190711-173347-3jgt7f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/283738/original/file-20190711-173347-3jgt7f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/283738/original/file-20190711-173347-3jgt7f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/283738/original/file-20190711-173347-3jgt7f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&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">Take precautions, like tucking pants into socks, when you’re in tick territory.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/protecting-against-ticks-by-tucking-pants-322456178?studio=1">rck_953/Shutterstock.com</a></span>
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<p>Overall, people should be aware of what tick-borne diseases are present in their area and use <a href="https://www.cdc.gov/ticks/avoid/on_people.html">personal protection techniques</a> whenever outdoors in tick-infested areas. Remember that ticks often come into close contact with people via pet dogs or cats. It’s a good idea to inspect yourself for ticks after being outdoors in tick-infested areas. Reducing the number of tick bites and the amount of time ticks remain attached can go a long way to protecting you from tick-borne diseases.</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/118102/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jerome Goddard 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>Tick-borne diseases are becoming more common in the United States. A public health entomologist outlines some of the lesser-known threats ticks pose to human health.Jerome Goddard, Extension Professor of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1063682018-11-07T13:10:46Z2018-11-07T13:10:46ZSouth Africa investigates sterilising mosquitoes in anti-malaria drive<figure><img src="https://images.theconversation.com/files/244111/original/file-20181106-74787-1d6j2in.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A close-up of a female Anopheles arabiensis feeding. </span> <span class="attribution"><span class="source">Author supplied</span></span></figcaption></figure><p>South Africa is one of four southern African countries aiming to <a href="https://medpharm.tandfonline.com/toc/ojid20/current">eliminate malaria transmission</a> by 2023. Indoor residual spraying using DDT and pyrethroid insecticides constitutes the backbone of South Africa’s <a href="http://www.samj.org.za/index.php/samj/article/view/7447/5462">malaria control programmes</a>. </p>
<p>Effective vector control by indoor residual spraying has been key in the reduction of malaria cases. This was instrumental in creating malaria-free zones in most parts of the country. Malaria transmission is now <a href="http://www.samj.org.za/index.php/samj/article/view/7441/5461">limited</a> to the north-eastern parts of Limpopo province, the low-veld areas of Mpumalanga province and the far northern parts of KwaZulu-Natal province. </p>
<p>Despite a concerted effort to eliminate malaria in these provinces, transmission has remained steady over the <a href="http://www.samj.org.za/index.php/samj/article/view/7441/5461">past decade</a>.</p>
<p>Failure to eliminate malaria transmission is attributed, in part, to resistance to the insecticides being used. Added to this is the challenge of controlling the outdoor-biting <em>Anopheles arabiensis</em> population that’s largely considered responsible for most malaria transmission in the country. </p>
<p>Indoor spraying isn’t completely effective against this mosquito because it mainly targets indoor biting and resting mosquitoes. This strategy is not adequate against vectors that sometimes feed and rest outdoors, such as <em>An. arabiensis</em>. </p>
<p>Other, complementary vector control strategies are needed to eliminate the disease. These must be able to control outdoor feeding and resting mosquito populations. </p>
<p>One possible approach is a technique that involves sterilising the insects. The technology is currently being assessed in South Africa. The technique involves a genetic birth control method in which laboratory mass-produced sterile male insects are released into the wild at a ratio that effectively inundates a target population. This forces most females to mate with sterile males, substantially reducing their fecundity, and resulting in population suppression. </p>
<p>The sterile insect technique has been piloted against <a href="https://www.springer.com/us/book/9781402060588">mosquito vectors</a> of the Zika, yellow fever, chikungunya and dengue viruses, but has never been used for malaria control efforts. The South African sterile insect technique initiative together with a similar trial in <a href="https://link.springer.com/chapter/10.1007/978-1-4020-6059-5_34">Sudan</a> are a first for African malaria vectors. </p>
<p>Preparations for the South African project are at an advanced stage. A pilot mass-rearing facility has been built and the size of the natural mosquito population has been estimated. In addition, a local community has been drawn into preparations and is now ready for a trial run. All these steps pave the way for a pilot demonstration.</p>
<h2>The project</h2>
<p>The sterile insect technique has been applied successfully against <a href="http://agris.fao.org/agris-search/search.do?recordID=US9032290">other insect pests</a> including the fruit fly and the new-world screwworm fly . In South Africa this technology is routinely used in Citrusdal, Western Cape to control the <a href="http://www.bioone.org/doi/abs/10.4001/003.023.0112">false codling moth</a>.</p>
<p>The <a href="http://www.parasitesandvectors.com/content/4/1/208">project</a> involving <em>An. arabiensis</em> aims to show that the sterile insect technique can be successfully used to suppress mosquito populations that carry and spread malaria. If it works, the approach can be used as an alternative vector control method to complement existing strategies. </p>
<p>The project is being implemented in three phases. </p>
<p>Phase 1 included trials showed that sterilised <em>An. arabiensis</em> males mass-reared under laboratory conditions can compete with fertile males for mates. This milestone informed phase II of the project which is currently underway.</p>
<p>This phase aims to test the feasibility of the sterile insect technique through a small-scale pilot field demonstration in northern KwaZulu-Natal. Research activities for phase II are in progress. The biggest development here is the building of Africa’s first pilot mosquito mass-rearing facility.</p>
<p>The sterile insect technique relies heavily on inundating the wild population with sterilised male insects. For this to succeed, it’s important to know the size of the wild mosquito population as this will determine how many laboratory-reared sterilised males would need to be released. </p>
<p>To estimate mosquito population numbers, a mark-release-recapture method was used. About 30,000 yellow and orange-dusted laboratory-reared males sharing the same genetic background as the wild population were released over two release periods. Some of these mosquitoes were recaptured together with wild mosquitoes and a formula was used to estimate the wild population size. </p>
<p>Interestingly, marked males were recaptured in swarms of wild males. This indicates that the laboratory-reared males were able to locate and participate in mating swarms – a crucial step for the potential success of the sterile insect technique.</p>
<h2>Next steps</h2>
<p>The eventual rollout of the pilot trial will require successful mass rearing of competitive sterile males and a technique to separate males from female insects. Work on optimising mass production of quality sterile male and a system to separate males from females are at an advanced stage. </p>
<p>In addition, it’s critical to get the community involved and addressing any social issues so that people cooperate and participate. This is particularly important because the sterile insect technique can be seen as increasing the numbers of mosquitoes in an area after the release of the sterile males. A malaria awareness campaign has already been conducted. Information on malaria transmission and control – including the potential of using the sterile insect technique – was shared through radio interviews, brochures, road shows and lectures in isiZulu.</p><img src="https://counter.theconversation.com/content/106368/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Givemore Munhenga receives funding from Department of Science and Technology, National Research Foundation and International Atomic Energy Agency. He is affiliated with University of the Witwatersrand. </span></em></p>South Africa is piloting a new technique as it drives to eliminate malaria.Givemore Munhenga, Senior Medical Scientist, National Institute for Communicable DiseasesLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/498482015-11-01T11:07:52Z2015-11-01T11:07:52ZParts of southern Africa are within tantalising reach of eliminating malaria<figure><img src="https://images.theconversation.com/files/100338/original/image-20151030-16554-1qj7h1i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A young girl plays inside a mosquito net in Kibera, Nairobi. </span> <span class="attribution"><span class="source">EPA/Stephen Morrison</span></span></figcaption></figure><p><em><em>This article is part of a series The Conversation Africa is running as part of the SADC malaria week. You can read the rest of the series <a href="https://theconversation.com/africa/topics/sadc-malaria-week">here</a>.</em></em></p>
<p>There has been a concerted international effort since the early 2000s to tackle malaria. This has led to dramatic reductions in the disease. </p>
<p>World Health Organisation estimates show that in 2015 there were <a href="http://www.who.int/malaria/media/malaria-mdg-target/en/">214 million</a> malaria cases and 438,000 deaths globally. This is a 37% decrease in the incidence rate of malaria compared to 15 years ago and a 60% reduction in deaths.</p>
<p>Most of the gains have happened in Asia and “fringe” areas in Africa, which is at the periphery of distribution of the disease. But the challenge is that sub-Saharan Africa still shoulders 89% of existing cases and 91% of deaths from the disease. </p>
<h2>How successes have been achieved</h2>
<p>Africa has historically had a high transmission rate. Southern Africa has been particularly successful in reducing its case load. The Seychelles and Mauritius have completely eliminated malaria. They have had no new local transmissions in recent years – only some imported cases that were locally diagnosed and treated.</p>
<p>In South Africa there was an exceptional peak of <a href="http://www.scielo.org.za/scielo.php?pid=S0256-95742013001000029&script=sci_arttext&tlng=es">64,622 cases</a> in 2000. Since then case numbers have dwindled to between 6000 and 10,000 in recent years. </p>
<p>This reflects reductions in several of South Africa’s neighbouring countries such as Botswana, Namibia, and Swaziland – where malaria mortality rates are close to zero. </p>
<p>These four countries are in the pre-elimination and elimination stages. Malaria incidence in all of them makes up less than five cases per thousand people. This means they are within sight of eliminating malaria – a tantalising target that South Africa hopes to reach <a href="http://www.scielo.org.za/scielo.php?pid=S0256-95742013001000035&script=sci_arttext&tlng=en">by 2018</a>.</p>
<p>But that reward is proving hard to achieve despite the dedicated efforts by the national malaria control programs in each country. </p>
<h2>The reasons why full elimination is so difficult</h2>
<p>The standard tools used almost universally for malaria control are: </p>
<ul>
<li><p>providing households with insecticide-treated bednets (ITNs);</p></li>
<li><p>indoor residual spraying (IRS) of insecticides against mosquitoes that enter households; and</p></li>
<li><p>dedicated efforts to detect malaria cases and treat them with effective anti-malarial drugs. </p></li>
</ul>
<p>When these three tools are used in combination, they have resulted in the reversal and decline in malaria cases almost globally. But what was once an effective approach to harvest the low-hanging fruit to achieve relatively quick success have now become blunt tools. </p>
<p>The interventions now lack the surgical precision to clear up what is known as “residual malaria”. These are the portion of cases that pop up for reasons that are not always known and do not yield to persistent use of the traditional tools.</p>
<p>A major contributing factor, especially in the case of South Africa, is the large numbers of migrants and visitors from high-transmission malaria countries further north. Although Gauteng, South Africa’s economic hub, was never a problem province, it now has the highest number of cases in the country.</p>
<p>The cases are through infected people entering the country and becoming ill once they have arrived, or vehicles returning from high-transmission countries with malaria-infected mosquitoes hitching a ride.</p>
<p>There are other reasons too. </p>
<p>Some countries do not have a policies to deal effectively with the particular life stages that infect mosquitoes. Malaria parasites have a complex life cycle involving different forms having different target organs and functions. Only one stage – the sexual gametocytes – are able to infect mosquitoes that leads to infecting other people. </p>
<p>Although doctors prescribe medication that kills the numerous asexual parasites in the blood which then cures infected people of the malaria symptoms, it does not effectively inactivate the sexual gametocytes that infect mosquitoes, at least in Africa where the deadliest species of malaria parasite is most common.</p>
<p>There are also chronic systemic challenges. These include a shortage of manpower, funding, lost skills that are not replaced, and a mindset still geared to the decades-long traditional approach to combat malaria. </p>
<h2>New frontier</h2>
<p>Entering the elimination stage is a relatively new frontier for the southern African countries. </p>
<p>There are more hazy possibilities that come into play with residual malaria. This includes the unknown role of secondary vectors. Traditional malaria control tools have targeted a very limited set of mainly <a href="http://www.parasitesandvectors.com/content/3/1/72">three mosquito species</a> with known behaviour. </p>
<p>Addressing these three species has resulted in successes. But with residual malaria we may be dealing with unknown secondary vector mosquitoes that previously played a minor role but now keep the disease ticking over.</p>
<p>Also, across the world there are increasing numbers of countries where mosquito populations are building resistance to available insecticides used for spraying. What is more concerning is that malaria parasites are also developing resistance to the only, and best, available anti-malarial compound, artemisinin.</p>
<p>This resistance is currently still confined to geographic pockets in southeast Asia, but precedents exist where such resistance rapidly spreads to other parts of the globe.</p>
<p>Another concern is loss of political will to continue the high financial and other demands associated with effective malaria programs – and donor fatigue. </p>
<p>Most of the money being poured into malaria control at global scale comes from international donors. Once again precedent has shown that in the face of diminishing returns such donors lose commitment.</p>
<h2>The last lap</h2>
<p>Botswana, Namibia, South Africa and Swaziland – unlike many other African countries confronted with particular economic and political challenges – are very likely to achieve zero local transmission. </p>
<p>The lessons learnt in South Africa and its neighbours is of great importance. There is some urgency in cementing these successes. </p>
<p>But then the real challenge will emerge: the will of national governments to continue funding a program that has achieved its goal. The moment it weakens its defences, malaria is likely to rebound extremely quickly in the face of migration and importation from high-transmission neighbouring countries that are still fighting to bring malaria under control.</p><img src="https://counter.theconversation.com/content/49848/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Professor Leo Braack received funding from Bill and Melinda Gates Foundation and University of Pretoria for research on malaria.</span></em></p>Several countries within southern Africa are on the brink of eliminating malaria. But there are several challenges ahead.Leo Braack, Research Chair, Integrated Vector Management in the Vector Control cluster at the Centre for Sustainable Malaria Control , University of PretoriaLicensed as Creative Commons – attribution, no derivatives.