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Explainer: Why Cholera remains a public health threat

Places with poor sanitation and insufficient clean drinking water are at risk of cholera outbreaks. Simon Akam/Reuters

Cholera has killed millions and remains a major threat to public health. The Conversation Africa’s Health and Medicine Editor Joy Wanja Muraya asked Dr Moses Masika to explain the nature of the disease and how it can be treated.

What is cholera? What is its history?

Cholera is an acute illness of the small intestine caused by a bacterium known as Vibrio cholerae.

It’s not a new disease: cholera has afflicted mankind for thousands of years. In the 19th century it spread from India to Asia, Europe and Africa because of trade and international travel.

For a long time it was widely accepted that cholera – and other diseases like malaria and bubonic plague – were caused by “bad air”. This was known as the miasma theory.

Then in 1854 there was an outbreak of cholera in a district in London. John Snow, a doctor working in the area, noticed that most of those who died from the outbreak had consumed water from a single public well in the district.

Snow removed the pump’s handle so no one could use the well anymore and the outbreak ended. People realised that cholera had nothing to do with “bad air”: it was water borne.

What are the symptoms?

Cholera causes no symptoms in most infected people because they don’t become ill and never know they’ve been infected.

Only about one in 10 infected people develop severe signs and symptoms, usually within a few days of infection

It causes profuse diarrhoea, sometimes accompanied by vomiting and abdominal pain. Patients can produce up to 20 litres of watery stool in a day.

Diarrhoea and vomiting leads to dehydration which, if not checked, can lead to shock which is insufficient blood flow to body organs that eventually causes organ failure and death. Patients with dehydration and shock may have a rapid heart rate, sunken eyeballs and cold, loose wrinkled skin.

Where is cholera endemic? Can you give an example of some recent large outbreaks?

Cholera is endemic in nearly 70 countries, most of them in Africa, South East Asia and South America. There are an estimated three million cases globally each year and about 100,000 deaths. That’s equivalent to 274 people dying every day.

The most vulnerable people are those who live in or travel to areas that lack clean drinking water as well as proper sanitation and hygiene infrastructure.

Natural disasters such as earthquakes and hurricanes which destroy sanitation infrastructure have also been associated with outbreaks. For example, a massive earthquake rocked Haiti in 2010 leading to the largest cholera outbreak in recent history.

There have been recent outbreaks in several countries in sub-Saharan Africa. In 2008 an outbreak in central, eastern, southern and west African states caused nearly 130,000 cases and more than 4,000 deaths.

Most countries in the region were affected and many are still experiencing active transmission of cholera. In 2014, a cholera outbreak was reported in Kenya. It has since spread to more than 30 of the country’s 47 counties causing over 15,000 cases and about 250 deaths.

In neighbouring South Sudan, an outbreak that began in June 2016 is spreading further across the country and has caused over 5,500 cases and 140 deaths.

Given the current rate of international travel, an infected person could travel to any part of the world in a day and place vulnerable populations at risk.

What are the best intervention measures and treatments?

The mainstay of cholera treatment is fluid replacement. The illness can cause dehydration rapidly and those who are suspected of having cholera should be taken to a health facility as soon as possible.

They should also take oral rehydration solution or other clean liquids on the way to hospital. Some patients may require intravenous fluids and correction of their electrolyte imbalance.

Antibiotics shorten the duration and reduce the severity of the disease. But fluid replacement is the priority.

If untreated cholera kills half of those infected due to dehydration and shock. Treatment can reduce this number to less than 1%.

How can communities and governments prevent cholera outbreaks?

Several measures can be deployed to control cholera.

  • Surveillance to promptly detect and report cholera cases. Public health authorities in endemic countries should have a mechanism of detecting, reporting and verifying suspected cases to nip an outbreak in the bud. There must also be information sharing among neighbouring regions, countries and global technical organisations such as the World Health Organisation. Information sharing helps to mobilise resources and contain an outbreak.

  • Hygiene and sanitation: this involves providing adequate clean and treated drinking water, proper waste disposal and sewerage systems.

  • Health education. The public should be alerted whenever there’s an outbreak and educated about the disease.

  • Prompt correct treatment: people suspected of having cholera should be diagnosed promptly and appropriately managed to prevent death and curtail the spread of the disease.

  • Vaccination: oral vaccines are available. These should be administered to travellers and people living in areas affected by cholera. But vaccination complements rather than replaces other control strategies. It prevents about two thirds of infections and works for a duration of two years after which a booster dose is required. Vaccinated individuals should still take precautions to avoid exposure to cholera.

  • Individual protection: people living in or travelling to cholera affected areas should take measures to prevent infection. Drink only boiled or treated water, avoid drinks and ice that may have been prepared with tap water, foods from street vendors, raw or under cooked food including sea foods and fruit salads. Only take fruit that you can peel or wash properly. As the travellers’ adage goes

Boil it, cook it, peel it or leave it!

Frequent handwashing with soap and water or alcohol based hand rubs is also helpful.

Finally, regional and national public health authorities should tap into the available networks to effectively control outbreaks.

There is a WHO Global Taskforce on Cholera Control to improve capacity development, coordination and implementation of evidence based cholera control strategies.

The WHO has also established a stockpile of cholera vaccines and response kits to ensure a prompt response to outbreaks.

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