Haitian Cholera Strain from South Asia

A cholera strain that has killed more than 2,000 people in Haiti since October is South Asian in origin, according to a study conducted by several Harvard affiliates, who matched bacteria samples from Haiti with ones from Bangladesh.

“Our main finding suggests, but does not prove, that the Haitian strain was introduced by some type of human activity from South Asia,” said Matthew K. Waldor, who organized the study and is a professor of medicine at Harvard Medical School, as well as an attending physician in infectious diseases at Harvard-affiliate Brigham and Women’s Hospital.

The cholera outbreak has spread to all provinces in Haiti, affecting approximately 80,000 people.

The results of the study appear to disprove the idea that the strain originated from the cholera epidemic in Peru in the early 1990s and was carried by ocean currents, which the scientists said had been one possible explanation.

Waldor’s lab conducted comparative genomics work on genomes from Haiti, Bangladesh, and Peru to conclude that the Haitian strain was similar to those circulating in South Asia and not similar to those in Latin America.

“The results show how infectious diseases can spread by global human travel and commerce,” Waldor said.

In order to sequence the genomes, Waldor collaborated with Pacific Biosciences, a biotechnology company in California.

The company is currently working on producing disease maps that sequence disease strains for large geographic regions to examine the origins of pathogens and the routes they take, according to the company’s Chief Scientific Officer Eric E. Schadt.

“When [Waldor] called, his study fit squarely in that type of project. Our technology is suited for sequencing genomes very quickly, whether for preventing an outbreak or treating patients,” Schadt said.

“There’s another technological implication that this newer [sequencing] technology that is ever better and faster and will transform the way we understand the spread of infectious diseases,” Waldor said.

Yet even before the study was conducted, Haitians had reportedly been blaming the Nepali people from the U.N. peacekeeping force for bringing in the cholera strain, according to Joia Mukherjee, the chief medical director at Partners in Health—a Harvard-affiliated non-governmental organization working in Haiti—and an associate professor of medicine at HMS.

The study only confirms those suspicions, Mukherjee said, adding that it is more important to change how peacekeeping is conducted.

“Some people say that aid workers should be vaccinated to protect themselves, but I think people going to [Haiti] should be vaccinated to protect the populace,” Mukherjee said.

—Staff writer Kerry M. Flynn can be reached at kflynn@college.harvard.edu.