Cholera strain in Haiti came from outside Latin America, linked to South Asia

The strain of cholera erupting in Haiti matches bacterial samples from South Asia and not those from Latin America, according to new findings published in The New England Journal of Medicine.

As previously reported in Infectious Diseases in Children, Herbert L. DuPont, MD, of St. Luke's Episcopal Hospital in Texas, said communicable pathogens such as Shigella were expected in the aftermath of the Jan. 12 earthquake, but cholera was not.

“Cholera has to be introduced into an environment,” DuPont said. “Something helped to produce this problem. Travelers may have brought it in. We would not have anticipated this.”

Matthew Waldor, MD, PhD, professor of medicine at Harvard Medical School and Brigham and Women’s Hospital, and colleagues said the bacteria introduced into Haiti most likely came from an infected human or contaminated food from outside of Latin America.

Waldor and colleagues used a third-generation, single-molecule DNA sequencing method to identify the probable origin of the Vibrio cholerae strain in Haiti. The researchers were able to determine the genome sequences of two Haitian cholera samples and three cholera samples from elsewhere around the world. Researchers observed a natural enzyme synthesizing a strand of DNA with advanced imaging technology, which allowed for a comprehensive analysis and comparison of critical DNA features among the various cholera samples.

Results of their analysis revealed a close relationship between the Haitian samples and the seventh pandemic variant strains isolated in Bangladesh in 2002 and 2008.

The cholera outbreak occurred close in time and place to the arrival of U.N. peacekeeping troops from South Asia, who may have introduced the bacteria. However, the researchers said determining the actual source of the strain will require further epidemiological investigation.

“Our data strongly suggest that the Haitian epidemic began with the introduction into Haiti of a cholera strain from a distant geographic source by human activity,” Waldor said in a press release. “Some scientists believe that the strain arose from the local aquatic environment, but this hypothesis is not supported by our analysis, which clearly distinguishes the Haitian strains from those circulating in Latin America and the US Gulf Coast.”

The researchers confirmed that it is highly unlikely that the outbreak was triggered by ocean currents or other climate-related events.

Because of the apparent human origin of the outbreak, the researchers suggest rapid screening for infection and vaccination for certain travelers and at-risk populations. In addition, the researchers call for global health officials to consider mass vaccination to control the spread of cholera, to limit the chance of mingling cholera strains producing more virulent strains, and to reduce the occurrence of future cholera epidemics.

The latest CDC data indicate that 91,770 cases of cholera have been reported, with 43,243 hospitalizations and 2,071 deaths. Of that number, 9,171 cases, 3,808 hospitalizations and 163 deaths occurred among children aged younger than 5 years.

Reports from the field show that death occurred as rapidly as 2 hours after symptom onset, which highlighted gaps in access to life-saving treatments, including oral rehydration solution, according to a recent dispatch from the Morbidity and Mortality Weekly Report.

For more information:

CDC. MMWR. 2010;59:1-5.

Waldor M. N Engl J Med. 2010.

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