Study bolsters theory on Haitian cholera outbreak's origin

A French epidemiological study conducted at the beginning of Haiti’s recent cholera outbreak builds a stronger link to the arrival of the disease alongside United Nations peacekeepers from Nepal than does a recent report by U.N. independent experts.

News of the group’s findings was leaked to the media in December, but the full findings did not appear until a May 6 online posting by the journal Emerging Infectious Diseases. The report details the French field investigation with collaboration from Haiti’s health ministry, according to CIDRAP News.

On May 4, an independent group of experts working on behalf of the U.N. announced the results of a five month investigation that stopped short of blaming the Nepalese peacekeepers for the outbreak. The group noted that human activity was the source of the outbreak, but said the disease could not have spread without deficiencies in Haiti’s water, sanitation and sewer systems.

In Haiti, there have been a reported 285,931 cases of cholera since the outbreak began, including the deaths of 4,870 people, according to the Pan American Health Organization.

When the outbreak first came to light, some public health officials were quick to link it to the devastating earthquake that occurred in Haiti in January 2010, CIDRAP News reports. At the time, rumors began to circulate that a contingent of sick Nepalese soldiers imported cholera into the country and spread it by dumping sewage into the Arbonite River.

An early analysis suggested that the Vibrio cholerae strain behind Haiti’s first cholera outbreak in a century came from outside the Caribbean, possibly from Asia or eastern Africa. Kathmandu, Nepal’s capital, reported a cholera epidemic in September, shortly before the peacekeepers arrival.

In as early as mid-October, French and Haitian investigators built a database to identify clusters and analyze the disease’s spread in the Arbonite River area, CIDRAP News reports. They conducted field interviews and explored the environmental risks in communities and cholera treatment centers.

The first patients were found to be a family living in Meille, a village that hosted a U.N. peacekeeping camp located above a stream that flowed into the Arbonite. The peacekeepers arrived at the camp shortly before the villagers became sick, and Haitian epidemiologists observed that a pipe discharged sewage into the stream from the camp. The villagers used the stream for cooking and drinking.

Cholera was later detected in Mirebalais, where local people were using the river while their water system was under repair. Prisoners at a local facility that obtained water from the river were also sickened.

The researchers said that the numbers of cholera cases in the area dropped soon after the sanitary problems at the camp were corrected, only to spike again in November, CIDRAP News reports. The outbreak was explosive in communities along the Lower Arbonite River and then spread into the Arbonite Basin.

The remoteness of Meille and the absence of other newcomers make it unlikely that a cholera strain might have been brought there another way. The research indicates that symptomatic cholera infections most likely occurred among the Nepalese inside the camp.

"Whatever its cause, this violent outbreak in Lower Artibonite provoked the flight of persons and resulted in a wave of epidemics that spread centrifugally and overwhelmed the nascent sanitarian response," the report says, CIDRAP News reports. "This wave explains the difference between the delayed and progressive starting of epidemics in the south and the immediate impact of cholera in the north."

The report does not pinpoint the exact contamination event, but researchers emphasized that the findings serve as a reminder that sewage needs to be handled appropriately and that aid organizations should avoid adding risks that do not already exist.