The cholera epidemic that has killed 1110 people and sickened thousands more in Haiti is part of a 49-year-old global pandemic and was likely brought to the Caribbean country by a single infected person, US Centres for Disease Control officials said the Morbidity and Mortality Weekly Report.
Many Haitians blame UN troops for bringing the deadly bacterial disease to the island nation, where 1.5 million people are still displaced after a devastating earthquake in January. Anti-UN riots have disrupted efforts to fight the raging cholera outbreak.
CDC infectious disease specialist Dr Scott Dowell said it may be impossible to trace how the cholera came to Haiti.
Genetic fingerprints show it can be traced to a pandemic that started in Indonesia 49 years ago and has spread around the world, the CDC and PAHO said.
"Surprisingly, it has spared the Caribbean so far," Dr Dowell said. "Cholera has moved quite efficiently around Haiti and also moved efficiently around the world. It's hard to figure out where it came from."
Dr Dowell said lives can be saved with quick and simple treatment and that is what health officials are focusing on.
Cholera can be treated with antibiotics, but the usual best course is giving intravenous fluids, salts and sugars to restore what is lost through diarrhoea and vomiting.
"As far as stamping it out or eliminating it from Haiti, we are not hopeful about that," Dowell said. "We feel that Haiti is going to be dealing with cholera for several years or several months at least."
Cholera is spread when the bacteria get into water, almost always via human waste.
Haiti had not seen cholera for 100 years but experts say the poorest country in the Western Hemisphere has near-perfect conditions for its spread - lack of proper sewage systems, people forced to defecate in the open, a tightly packed population, torrential rains and a lack of access to clean water.
Genetic tests show the Vibrio cholerae bacteria from many samples are almost identical to one another, which supports the theory of a single source, the CDC and PAHO said.
"If these isolates are representative of those currently circulating in Haiti, the findings suggest that V. cholerae was likely introduced into Haiti in one event," the researchers wrote in the CDC's weekly report on death and disease.
"V. cholerae strains that are indistinguishable from the outbreak strain by all methods used have previously been found in countries in South Asia and elsewhere," they said.
"Haiti is the latest country to be affected by the ongoing cholera pandemic, which began 49 years ago in Sulawesi, Indonesia, and has lasted longer and spread farther than any previously known cholera pandemic."
Most of the first cholera patients in Haiti worked in rice paddies in the Artibonite Department.
Health investigators interviewed 27 patients. The report said most reported drinking untreated water from the Artibonite River or canals and 78% practiced open defecation.
"This is the breadbasket of Haiti," Dowell said. "If cholera gets into the Artibonite River, it gets distributed across Artibonite pretty efficiently. People have a lot of contact with river water."
Before the earthquake hit, only 12% of Haiti's population had piped, treated water and only 17% had access to adequate sanitation, the CDC and PAHO said. Now the situation is worse.
Conditions favourable for cholera
"The course of the cholera outbreak in Haiti is difficult to predict," the researchers concluded. "The Haitian population has no pre-existing immunity to cholera, and environmental conditions in Haiti are favourable for its continued spread."
Camps for Haitians displaced by the earthquake lack hand-washing facilities and many do not have clean water.
"The number of cases might be lowered substantially if efforts to reduce transmission are implemented fully, but they also might be increased substantially by delays in implementation, flooding or other disruptions," the report said.
The World Health Organisation reports that 221,226 cases of cholera and 4,946 deaths from the infection were reported from 45 countries in 2009 but the true toll was likely much higher.
(Reuters Health, Maggie Fox, November 2010)