Clonal origins of Haiti’s Cholera epidemic

Haiti had been free of cholera for 50 years when the earthquake struck in January 2010. The destruction of Haiti’s infrastructure by the earthquake made it vulnerable to infectious disease outbreaks but it was hoped that cholera would pass it by. As we all know by now, this unfortunately has not been the case. Cholera has spread extensively throughout the country and it is feared that with the vast infrastructure damage, it will become entrenched in Haiti.

Finding the source of the epidemic has been politically sensitive locally and internationally. While locals may be quick to accuse outsiders of increasing their misery, determining the exact origin of the bacteria is necessary to understand the outbreak and determine long-term response. Spread of Vibrio cholerae from the South American outbreak that started in Peru in 1991 or the gulf shore of the United States has been ruled out. Several groups have produced results that point toward a south Asian origin but no one has been able to conclusively prove that it came from Nepalese peacekeepers who have shouldered most the blame to date.

A forthcoming report by Ali et al in the April issue of Emerging Infectious Disease confirms a recent clonal origin for specimens taken within the first three weeks of the epidemic. Of the specimens  taken from 19 diarrhea patients in St Mark’s hospital, Artibonite, 16 patients had the altered El Tor biotype of  Vibrio cholerae O1 Ogawa with the classical cholera B toxin gene. Genetic analysis was unable to pinpoint an origin location for this strain. The lack of VNTR diversity suggests a clonal expansion of a point-source outbreak along the Artibonite river. Ali et al do not believe that this strain could have come from a long-standing environmental reservoir in Haiti because of the lack of diversity and the relatively recent origin of the El Tor  biotype.

Ali, A., Chen,Y.,  Johnson, J.A,  Redden, E., Mayette, Y.,   Rashid, M.H.,  Stine, O.C., and Morris,  J.G. (2011). Recent Clonal Origin of Cholera in Haiti. Emerging Infectious Disease, 17 (4 — April) : 10.3201/eid1704.101973

Expedited release of this article can be found here (as of Feb 20, 2011).

Enserink M (2011). Epidemiology. Despite sensitivities, scientists seek to solve Haiti’s cholera riddle. Science (New York, N.Y.), 331 (6016), 388-9 PMID: 21273460

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