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PLOS BLOGS Speaking of Medicine and Health

Evidently it’s Cholera Season

Just when the oppressive summer heat and humidity in South Asia seem no longer tolerable, especially to this Northern expatriate new to Bangladesh, the rains come, bringing relief in the form of cooler temperatures, fresh air, and sparkling trees and flowers.

What also comes with the monsoons is a reprieve from cholera.

Cholera is a form of acute watery diarrhoea, which spreads from person to person through food and water contaminated with the bacterium Vibrio cholerae. It is a miserable condition involving massive fluid loss and dehydration and left untreated can rapidly decline to death. Cholera is common in places with poor water and sanitation and sometimes causes large epidemics with thousands of people falling ill. Haiti’s cholera epidemic following the 2010 earthquake has killed more than 8000 people. The outbreak in South Sudan, currently affecting about 1500 people, is said to be worsening. In Bangladesh, where cholera is endemic, regular outbreaks are a fact of life and well-managed. Still, WHO estimates 3–5 million cases and up to 120,000 cholera deaths each year around the world.

At the public health research institution icddr,b (where I am an employee), our Dhaka Hospital sees about 300 people a day suffering from diarrheal diseases, but just before and after the monsoon this number can spike to as many as 1000 per day. Yes: 1000 patients per day, many with bodies ravaged by the dehydration and sometimes wasting that cholera can cause. Doubling the capacity of the hospital, beds known as ‘cholera cots’ occupy every available space and icddr,b erects massive tents to absorb the patient load. These tents can inhabit our entire parking lot.

TENT(Flood)14 AUG.07.12_Scaled
Image Credit: icddr,b

Despite these incredible numbers, diarrheal patients are treated with remarkable efficiency and effectiveness – many going home the same day; the mortality rate for those without other health problems is said to be under 1%.  Early diagnosis and treatment are key. First line approaches are oral rehydration salts (ORS) – the simple, low cost medical innovation developed by researchers at icddr,b in the 1960s – or intravenous fluids in more severe cases. The majority of patients respond to ORS, a simple solution of sugar, salt, and water. To say hundreds of lives a day are saved at Dhaka Hospital is no overstatement – and at about US10 dollars per uncomplicated case it is perhaps the epitome of simple, low cost solutions for health. (ORS sachets themselves are only 15 cents a piece).

But there are other scenarios where treatment for cholera may require something other or more than ORS and fluids, and this month there is new evidence to better guide treatment.

First, more severe forms of diarrhea or in situations where ORS alone is inadequate may mean a preference for antibiotics. In a comprehensive and independent review that represents the biggest and best collection of evidence so far, a group of infectious disease researchers affiliated with the Cochrane Collaboration analysed all the available data from clinical trials on antibiotics for cholera. Antibiotic treatment shortened the duration of diarrhoea by about a day and a half (the normal duration is 3-4 days), and reduced the total amount of diarrhoea by half. This then cuts the need for rehydration fluids by half. By reducing the duration of the bacteria being present in diarrhea, antibiotics shortened the time the patient is contagious. Benefits were evident for patients with severe and less severe levels of dehydration.

Second, in outbreak scenarios treatment plans may turn to vaccines. Because cholera is contagious and rapidly acting, outbreaks can be explosive. Some have questioned whether resources required to purchase and deploy vaccines across the affected populations would be better spent on basic water and sanitation infrastructure. But new research is strengthening the evidence for implementing cholera vaccination programmes as one part of a comprehensive plan to prevent, treat, and eliminate this deadly disease. A new study from an outbreak in Guinea, funded by Médecins sans Frontières, shows that two doses of an oral cholera vaccine, Shanchol, were able to protect people by 86%. Shanchol had previously been shown to be safe and efficacious in larger trials, and it is cheap: two doses cost about $3, or about one-tenth the price of the only other WHO-pre-approved vaccine Dukoral. This adds to evidence supporting the use of vaccines in the short term and/or in outbreak situations, while recognizing that longer term goals for improving water and sanitation are needed.

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