Researchers at two Boston hospitals have sequenced the DNA of the cholera bacteria and compared it with strains from Peru, Bangladesh, the Gulf of Mexico region and other areas, NewScientist.com reported Friday.
The analysis showed the Haitian bacteria were from a single source and similar to a recent predominant South Asian strain, but a different lineage to cholera in South America or strains occurring naturally in the Gulf of Mexico.
"The bottom line is, this cholera was introduced by human activity from thousands of miles away," Matt Waldor of Brigham and Women's Hospital in Boston says.
Two mutations found in both South Asian and Haitian bacteria mean they are the "classical" toxin seen in pandemics before the 1960s, a toxin believed to cause worse disease than the cholera strain that has been spreading around the world since 1961.
Researchers say the Haitian toxin also carries a third mutation that appeared in 2002 in Bangladesh and was until very recently found only in South Asia.
This is unfortunate news, scientists say, as the Haitian strain carries more antibiotic-resistance genes than South American cholera.
The mutant toxin also seems to cause more intense diarrhea, cholera's fatal symptom.
The U.S. Centers for Disease Control and Prevention reports some victims in Haiti have died just 2 hours after first getting symptoms.