UN peacekeepers from Nepal brought the strain of cholera to Haiti responsible for an epidemic that has killed 5,500 people, according to a study published by the US Centers for Disease Control and Prevention.
The study is the first to establish a direct link between the arrival of the Nepalese UN battalion near the small town of Mirebalais and the cholera epidemic that erupted in mid-October 2010.
On Thursday in New York, UN acting deputy spokesman Farhan Haq said the agency was "aware of the report and as with other prior reports, we will study its findings diligently."
The research, led by a group of French doctors, appeared in the CDC's July issue of "Emerging Infectious Diseases."
"There was an exact correlation in time and places between the arrival of a Nepalese battalion from an area experiencing a cholera outbreak and the appearance of the first cases in Meille a few days after," write the eight authors of the report.
"The remoteness of Meille in central Haiti and the absence of report of other incomers make it unlikely that a cholera strain might have been brought there another way," they added.
The cholera outbreak's long-suspected connection to the Nepalese troops provoked bloody anti-UN riots in the country in November that led to two deaths.
Cholera is rare in Haiti -- last year's outbreak was the first in more than a century -- and came as a surprise to country health officials.
The disease is caused by bacteria spread in contaminated water or food, often through feces. If untreated, it can kill within a day through dehydration, with the old and the young the most vulnerable.
According to the CDC study, sewage from the UN camp poured into the Meille River, which greatly accelerated the spread of the disease. The Meille, in turn, flowed into Haiti's longest and most important river, the Artibonite.
"We believe that Meille River acted as a vector of cholera during the first days of the epidemic by carrying sufficient concentrations of the bacterium to induce cholera in persons who drank it," the authors concluded.
The cholera then flowed from the Meille into the Artibonite.
"Our field investigations, as well as statistical analyses, showed that the contamination occurred simultaneously in the seven communes of the lower course of the Artibonite River."
A UN report written by four international experts and released in May said the source of the epidemic was "debatable" but that the United Nations "worldwide" must change the way it handles peacekeepers' health.
But that report said evidence "overwhelmingly supports" the conclusion that the Haiti epidemic was due to the contamination of a river near the Nepalese camp "with a pathogenic strain of current South Asian type" of cholera.
Since the outbreak began, Haiti's Ministry of Health has recorded 5,506 deaths and 363,117 diagnosed cholera cases.