Cholera may have arrived on island 'years ago' from Asia

Medical briefing

The source of the cholera outbreak in Haiti is unlikely to be established with certainty, a leading expert on the disease said yesterday.

The bacterium Vibrio cholerae, which causes watery diarrhoea, vomiting and has so far killed 900 people in the country's refugee camps, may have lain dormant for years or been introduced from the United States, said Sandy Cairncross, a professor of environmental health at the London School of Hygiene and Tropical Medicine.

Nepalese peacekeepers have been blamed for the outbreak after the disease was identified as a South-east Asian strain. Cholera is endemic in Nepal and the first cases were reported in Mirebalais, 60km north-east of the capital, Port-au-Prince, near a military camp housing Nepalese soldiers.

Other cases occurred further down the Artibonite River and it was reported that sewage pipes led from the camp to a nearby stream, which emptied into the Artibonite. But tests on water samples from the stream found no bacteria. Professor Cairncross said South-east Asia was the natural home of cholera, where the disease had always been endemic.

"Most known strains come from South-east Asia," he said. "But they could have got to Haiti some years ago or they could have got to the US and only been transmitted to Haiti recently."

Cholera is excreted in faeces and transmitted by contaminated water, food or hands. For a century after the bacterium was discovered by the German Physician Robert Koch in 1883 it was thought the only stable place it could be found was the human gut.

But after an outbreak during the 1980s in the US, the cholera bacterium was discovered in salty coastal lagoons in Chesapeake Bay, in Australian creeks and in the Kent marshes in England. Scientists found the bacterium could lie dormant, living in conjunction with blue-green algae, for years.

"Its normal habitat is surface water," Professor Cairncross said.