Second cholera strain identified in Haiti epidemic

Researchers in the United States have determined that a second strain of cholera was involved in the Haiti epidemic in 2010-2011 that killed an estimated 7,500 people and sickened 500,000.

While previous studies suggested the epidemic was caused entirely by a strain of bacteria introduced inadvertently by Nepalese peacekeepers, the new strain appears to be of local origin. The new strain's role in the epidemic is not clear because it does not typically lead to epidemics, the Los Angeles Times reports.

The cholera outbreak occurred in the wake of a magnitude seven earthquake on January 12, 2010, followed by approximately 52 aftershocks of magnitude 4.5 or higher. Approximately 250,000 people died immediately, 300,000 were injured and one million were made homeless. Cholera cases started to appear in October 2010.

Early studies showed that the primary cause of the epidemic was the Vibrio cholerae 01, a strain of cholera found in Asia. The new study sequenced the cholera bacterium in 76 samples from Haitian cholera victims, according to Los Angeles Times.

According to a report in the Proceedings of the National Academy of Sciences, 47 of the samples contained the V. cholerae 01 strain, but 29 of the samples contained V. cholerae non-01/0139 strains. The latter strains are routinely found in estuaries and waterways in the western hemisphere and are not thought to be able to cause epidemics. The researchers determined that the strain must be able to produce an epidemic either in concert with V. cholerae 01 or on its own.