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Haiti's cholera outbreak will go from bad to worse

The cholera epidemic in Haiti is just getting started. Disagreements over who, or what, was responsible for the epidemic continue, and health agencies predict the situation will get much worse before cases start falling. Yet good vaccines are going unused. New Scientist rounds up the latest news.

What is happening in Haiti?

Cholera broke out in Haiti on 19 October, and from the outset doctors feared they could not contain it. The bacteria spread in water contaminated with infected faeces. Only half the population of Haiti had access to proper sanitation, and only a third had clean drinking water, even before the devastating earthquake in January. Now conditions are even worse. As a result, cholera has spread throughout Haiti, and as of 29 November, the outbreak had caused 1721 deaths.

That's just for starters. Epidemics grow exponentially: case numbers rise slowly at first, then take off. Cholera cases in Haiti are rising faster than predicted, and health agencies now forecast that 400,000 people will be infected in this outbreak, at least half in the next three months. Only 2.3 per cent of cases are leading to death, partly because many get prompt rehydration therapy, but ominously doctors are already struggling with the current case load.

Why is cholera such an emergency? Wasn't Haiti already plagued with disease?

Yes, but not cholera. The seventh pandemic of cholera, currently ongoing, started in south Asia in 1961 and hit Peru in 1991. It hadn't reached the Caribbean before, so Haitians have had little experience with managing cholera, and no immunity. This strain also carries a virulent toxin found in earlier pandemics.

Isn't there a vaccine?

There are three vaccines, all oral and made of dead cholera bacteria. One has been used successfully in emergencies among refugees in Asia and Africa. Another appears to work in one dose, rather than the usual two, so could protect people fast enough to slow a cholera epidemic in mid-outbreak, says John Clemens of the International Vaccine Institute in Seoul, South Korea.

Yet the Haitian government's strategy for fighting this outbreak does not mention vaccines. The problem, says Peter Hotez of George Washington University in Washington DC, is there are "too few doses on hand". People in regions in which cholera is prevalent, such as Africa, do not use much vaccine as the immunity the vaccines elicit does not last long. Vaccines are mostly used by travellers, so only small quantities are produced.

Cheap, single-dose vaccines made of live weakened bacteria that confer long-term immunity could change that, and are in "advanced stages of development", says Matthew Waldor of Harvard Medical School in Boston. But for now, Waldor, Clemens and Hotez, writing in The New England Journal of Medicine are calling for a global stockpile of cholera vaccine so there will be enough for emergencies such as Haiti. The World Health Organization already stockpiles yellow fever and meningitis vaccines.
 
 

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