The V. cholerae strain responsible for the expanding cholera epidemic in Haiti is nearly identical to so-called variant seventh-pandemic El Tor O1 strains that are predominant in South Asia, including Bangladesh.23,24 The shared ancestry of the Haitian epidemic strain and recent South Asian strains of V. cholerae is distinct from that of circulating Latin American and East African strains of V. cholerae. Patterns of DNA from Haitian strains and V. cholerae strains in a large collection held by the CDC, as determined by means of pulsed-field gel electrophoresis, also suggested that the Haitian strains of V. cholerae are most similar to recent South Asian V. cholerae strains.3 Our comparative analysis of the H1 and H2 strains and three CDC isolates indicate that the Haitian cholera epidemic is clonal. Collectively, our data strongly suggest that the Haitian epidemic began with introduction of a V. cholerae strain into Haiti by human activity from a distant geographic source.
New England Journal of Medicine
December 9, 2010