The cholera epidemic that has killed 1,110 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, scientists said on Thursday.
Haiti's epidemic could easily worsen despite efforts to control it, the U.S. Centers for Disease Control and Prevention and the Pan American Health Organization said.
Many Haitians blame U.N. 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-U.N. riots in the city of Cap-Haitien have disrupted efforts to fight cholera there.
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 it has near-perfect conditions for its spread -- lack of proper sewerage, 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 flooded rice fields in the Artibonite Department. Health investigators interviewed 27 patients.
The CDC report said most of them reported drinking untreated water from the Artibonite River or canals and 78 percent practiced open defecation.
Before the earthquake hit, only 12 percent of Haiti's population had piped, treated water and only 17 percent had access to adequate sanitation, the CDC and PAHO said. Now the situation is worse.
"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 favorable for its continued spread."
Camps for more than 1 million Haitians displaced by the earthquake lack handwashing 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.
"Longer-term persistence of V. cholerae in the environment in Haiti and recurrent cholera outbreaks also are possible."
Cholera can be treated with antibiotics but the usual best treatment is giving intravenous fluids, salts and sugars to restore what is lost through diarrhea and vomiting.
"The cholera outbreak in Haiti underscores the continuing vulnerability of much of the world's population to sudden severe illness and death from cholera," the report said.
"In 2009, a total of 221,226 cases of cholera and 4,946 cholera deaths were reported to the World Health Organization (WHO) from 45 countries; however, the actual number of annual cases is thought to be substantially higher."