FP Explainer

Did U.N. Peacekeepers Bring Cholera to Haiti?

Not necessarily.

Efforts to combat Haiti's rapidly spreading cholera outbreak, which has so far killed more than 1,000 people in the country, were hampered this week by widespread anti-U.N. rioting in the country's north. The rioting has forced the United Nations and nongovernmental agencies to suspend the delivery of badly needed medical and sanitation supplies. The violence is thought to be partly the result of Haitians' longstanding resentment of the 12,000-member U.N. peacekeeping mission in the country, but has also been caused by the widespread belief that the peacekeepers themselves introduced the disease. Could that possibly be true?

Perhaps, but it's far from certain. Haiti has not had a cholera outbreak in several decades, while Nepal, where many of the peacekeepers are from, is currently suffering one. Media attention has focused on the U.N. camp near the northern city of Cap-Haitien, the epicenter of the outbreak, which has poor sanitation facilities and is located near a river. Additionally, the initial tests by the U.S. Centers for Disease Control (CDC) indicate that the particular strain of cholera currently plaguing Haiti matches one found in South Asia. Despite these clues, there's still a very good chance that cholera was present in Haiti long before the Nepalese troops arrived.

The bacteria that cause cholera can exist in an environment, usually an enclosed body of water, for long periods before infecting a human population. (The bacteria have even been found in the Chesapeake Bay.) When the bacteria are ingested, the human intestine acts as an incubator for the disease, making it more virulent. (Not everyone who ingests cholera will get sick; an individual's overall health and genetic disposition also play a role.) When the person then excretes the bacteria back into the environment through defecation, the disease can spread though a population's water supply.

It's not unprecedented for cholera to suddenly break out in an area with little warning. A cholera epidemic broke out in Peru in 1991 after the disease hadn't been seen in South America in more than a century. Later tests revealed that the bacteria had been present in the water supply for some time. While there are hundreds of serotypes -- or varieties -- of cholera, only a few are virulent enough to cause outbreaks. Over time, however, the virulent and nonvirulent types cross-breed and produce new genetic configurations, increasingly the likelihood that someone will ingest them.

In modern times, cholera outbreaks almost invariably occur in places with poor sanitation and little access to clean drinking water. In the case of Haiti, many doctors are less surprised by cholera's emergence than by the fact that it hadn't happened sooner. One University of Florida microbiologist had in fact warned of the likelihood of a cholera outbreak after a trip to Haiti this past summer -- several months before the outbreak.

The CDC test is also not necessarily conclusive. Outside observers say the center's tests are not as specific as those used by other organizations and more research is needed to pinpoint exactly which strain is present in Haiti. The CDC itself says that despite the similarity of the disease to South Asian strains, it's not possible to accurately pinpoint the source.

Public health experts debate whether it's even worth the effort to trying to find out where the disease come from at a time when scarce resources are being devoted to halting its spread. The World Health Organization has said that investigating the origin of the outbreak is "not important right now," though longtime Haiti public-health advocate and U.N. deputy special envoy Paul Farmer counters that finding the source "would seem to be a good enterprise in terms of public health" and that the reluctance of international organizations to investigate further is politically motivated.

For its part, the U.N. peacekeeping mission says that medical tests on its troops showed no signs of cholera. But that answer is unlikely to satisfy the desperate protesters on the streets of Cap-Haitien.

Thanks to David Sack, professor of global disease epidemiology and control at the Bloomberg School of Public Health at Johns Hopkins University.    

Spencer Platt/Getty Images

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