Evidence "strongly suggests" that a United Nations peacekeeping mission brought a cholera strain to Haiti that has killed thousands of people, a study by a team of epidemiologists and physicians says.
The study is the strongest argument yet that newly arrived Nepalese peacekeepers at a base near the town of Mirebalais brought with them the cholera, which spread through the waterways of the Artibonite region and elsewhere in the impoverished Caribbean country.
The disease has killed more than 5,500 people and sickened more than 363,000 others since it was discovered in October, according to the Haitian government.
"Our findings strongly suggest that contamination of the Artibonite [river] and one of its tributaries downstream from a military camp triggered the epidemic," said the report in the July issue of Emerging Infectious Diseases, a journal of the U.S. Centers for Disease Control and Prevention.
The article says there is "an exact correlation" in time and place between the arrival of a Nepalese battalion from an area of its South Asian homeland that was experiencing a cholera outbreak and the appearance of the first cases in the Meille River a few days later.
The remoteness of the Meille River in central Haiti and the absence of other factors make it unlikely that the cholera strain could have come to Haiti in any other way, the report says.
'Confluence of circumstances,' UN says
In an email, UN mission spokeswoman Sylvie Van Den Wildenberg didn't comment on the findings of the article published in the CDC journal, referring only to a study released in May by a UN-appointed panel.
That panel's report found that the cholera outbreak was caused by a South Asian strain imported by human activity that contaminated the Meille River where the UN base of the Nepalese peacekeepers is located. The study also found that bad sanitation at the camp would have made contamination of the water system possible.
But the UN report refrained from blaming any single group for the outbreak. While no other potential source of the bacteria itself was named, the report attributed the outbreak to a "confluence of circumstances," including a lack of water infrastructure in Haiti and Haitians' dependence on the river system.
The panel's report was ordered by UN Secretary General Ban Ki-moon as anti-UN protests spread in Haiti and mounting circumstantial evidence pointed to the troops.
Before that, for nearly two months after the outbreak last October, the United Nations, CDC and World Health Organization refused to investigate the origin of the cholera, saying that it was more important to treat patients than to try to figure out the source.
The article published in the CDC journal comes as health workers in Haiti wrestle with a spike in the number of cholera cases brought on by several weeks of rainfall. The aid group Oxfam said earlier this month that its workers were treating more than 300 new cases a day, more than three times what they saw when the disease peaked in the fall.
Cholera is caused by a bacteria that produces severe diarrhea and is contracted by eating or drinking contaminated food or water.
Dominican Republic deaths reported
The disease has spread to the neighbouring Dominican Republic, where more than 36 deaths have been reported since November.
Epidemiologist Renaud Piarroux, the lead author of the CDC journal article, was initially sent by the French government in late 2010 to investigate the origins of Haiti's outbreak. He authored a report for UN and Haitian officials that said the Nepalese peacekeepers likely caused the outbreak, a copy of which was obtained at the time by the AP.
The latest study was more complete and its methodology was reviewed by a group of scientists.
The new study argues it is important for scientists to determine the origin of cholera outbreaks and how they spread in order to eliminate "accidentally imported disease." Moreover, the study says, figuring out the source of a cholera epidemic would help health workers better treat and prevent cholera by minimizing the "distrust associated with the widespread suspicions of a coverup of a deliberate importation of cholera."
It also argues that demonstrating an imported origin would compel "international organizations to reappraise their procedures."
After cholera surfaced last fall, many Haitians believed the Nepalese peacekeepers were to blame, straining relations between the population and UN personnel and sparking angry protests. On the streets, cholera has become slang for something that must be banished from Haiti.
The new study is acknowledged in a commentary by a pair of public health experts affiliated with the CDC.
"However it occurred, there is little doubt that the organism was introduced to Haiti by a traveler from abroad, and this fact raises important public health considerations," wrote Scott Dowell, director of the CDC's Division of Global Disease Detection and Emergency Response, and Christopher Braden, a medical epidemiologist with the CDC.