Study: Origin of cholera epidemic in Haiti is in humans, not nature

After studying the DNA of the strain of cholera responsible for the outbreak in Haiti, researchers believe this disease was brought to the Caribbean nation by humans.

Researchers used cutting-edge DNA testing to identify the origins of the bacteria responsible for the large cholera outbreak.  By sequencing the genome of this strain and analyzing the DNA from strains found in Latin America and South Asia, researchers found this Haitian strain of cholera is nearly identical to strains circulating in South Asia, according to a study published online in the New England Journal of Medicine on Thursday.  However, it was distinct from the strain in Latin America, says lead author Dr. Matthew Waldor, a physician and researcher at the Harvard School of Medicine.

Since the strain from this large outbreak matches the strains from South Asia, which is so far from Haiti, Waldor and his co-authors conclude the disease came into the country through human activity, rather than coming from environmental means such as ocean currents, which was another hypothesis because cholera can be found in brackish bodies of water.

Health officials on the ground trying to contain this rapidly spreading infection that in the most serious cases can kill within hours if left untreated, tell CNN that the origin of this epidemic is less important than treating those already sickened and preventing further spread.

However Waldor says by analyzing the genetics of this strain in Haiti, he and his co-authors were able to learn that this bacterium has a form of cholera toxin that is probably more virulent and therefore makes the disease more harmful and spreads more rapidly.

Waldor says figuring out how cholera got to Haiti is important, so this type of outbreak can be prevented in the future.  It's not about blaming any particular group, he says, but knowledge is power and lessons can be learned. He suggests before people leave an area where cholera is prevalent to go help those in an area where this disease has been absent, they should be screened and either given an antibiotic or a vaccine to prevent the possible spread of this disease.

UN peacekeepers from Nepal have already been blamed as being the source of the outbreak because the first cases of cholera were found near their camp, which have led to riots. Just yesterday a report by a French scientist surfaced suggesting the Nepalese soldiers are the most likely source of the outbreak.

Waldor and his co-author Dr. Eric Schadt, who is the chief scientist of Pacific Biosciences in Menlo Park, California where the genomes of the cholera strains were sequenced both insist their research does not confirm the Nepalese link. That's because they did not have a sample of a Nepalese cholera strain to compare it to.

Using third generation DNA sequencing technology, Schadt says it took less than a day for his lab to decipher for the genetic make-up of the cholera strains.  His laboratory's results confirm earlier testing reported last month by the Centers for Disease Control and Prevention, which used an older, slower method for DNA fingerprinting.
Being able to analyze a strain so quickly will help health officials in the future according to Schadt. He believes the main message is that this is a global disease now that these things are being carried from far-away places.

So far almost 100,000 people have been sickened in Haiti and more than 2,000 have died.