The evidence "overwhelmingly" suggests that cholera was inadvertently introduced to Haiti by U.N. peacekeepers, an independent panel concludes in a report to U.N. Secretary-General Ban Ki-moon that was released yesterday. The report relies on a review of the genetic and epidemiological data as well as a study of the sanitation system of a U.N. camp near the site of the first cases. While careful not to assign blame, the report has a series of recommendations to prevent similar catastrophes in the future, including screening U.N. personnel from cholera-endemic areas for the presence of Vibrio cholerae before they leave home and giving them a prophylactic dose of antibiotics.
Soon after the start of the outbreak, which has sickened close to 300,000 people and killed nearly 5000, Haitians fingered the United Nations Stabilization Mission in Haiti (MINUSTAH), which has a camp populated by Nepalese soldiers in Mirebalais in the Centre Department, very close to where the first cholera cases occurred. The camp was also blamed in a leaked epidemiological report by a French cholera expert, Renaud Piarroux of the University of the Mediterranean in Marseille, written at the request of the Haitian government. Several genetic studies showed that the Haitian cholera strain strongly resembled others found recently in South Asia—although none pinpointed Nepal specifically.
Yet some cholera scientists—including Rita Colwell, seen by many as a giant in the field—contended that the bacteria had more likely been present in local waters, and that the outbreak had been triggered by a combination of environmental factors.
The four-member panel, chaired by Alejandro Cravioto of the International Center for Diarrhoeal Disease Research, Bangladesh, unambiguously rejects that theory. Microbes isolated from patients in different parts of Haiti are genetically identical, suggesting an introduction at a single point, the report says. Genetically, the Haiti strain is very similar to South Asian strains of V. cholerae. "The analysis of available data refutes the argument that the Haitian strains arose indigenously from the Haitian environment," the panel writes.
Mirebalais, the site of a Nepalese MINUSTAH camp, is most likely the place where that point of introduction happened, the panel concludes. Not only did the first cases occur there, but the times at which new cases occurred a few days later down the Artibonite River—given the water velocity—are consistent with an introduction near Mirebalais that was carried downstream by the river.
Moreover, there was ample opportunity for cholera microbes to enter the Meye Tributary System of the Artibonite River in and around the Nepalese camp. At the camp, so-called "black water"—that is, water containing human fecal material—was collected in six 2500 liter fiberglass tanks. But the piping in the camp's main showering and toilet area was shoddy, and there was "significant potential" for waste water to leak into a drainage ditch that runs throughout the camp and ends up in the Meye system.
Another possible contamination site was just outside the camp. Twice a week, a Haitian contractor would send a truck to collect sewage from the camp's containers and haul it to an open septic pit (pictured) on a nearby hilltop that was far from secure. "There is no fence around the site, and children were observed playing and animals roaming in the area around the pit," says the report. The pit would overflow into the Meye tributary system during rainfall.
Wastewater from two other camps for Nepalese MINUSATH forces in the Centre Department (called Hinche and Terre Rouge) was also trucked to the pit, which means they, too, could be at the origin of the outbreak.
The report concludes that sanitation in and around the MINUSTAH camps was "not sufficient," and recommends that U.N. installations worldwide "treat fecal waste using on-site systems that inactivate pathogens before disposal." But—perhaps so as not to fan the flames—it stops short of blaming the Nepalese or MINUSTAH. Instead, the report stresses that the disease became a major disaster as a result of a series of circumstances, including Haiti's poor drinking water and sanitation infrastructure and lack of medical services. The outbreak "was not the fault of, or deliberate action of, a group or individual," it says.
Researchers say the report should put the scientific controversy to rest. "I'm personally gratified that I was able to read the tea leaves correctly, because God knows I took quite a bit of flack from colleagues," says molecular biologist John Mekalanos of Harvard Medical School in Boston, who published evidence that the strain came from South Asia in a paper in The New England Journal of Medicine in January.
Piarroux, who had been worried that the truth might never come out, says he feels vindicated because the report confirms most of the conclusions in his report to the Haitian government. "They did a great job," he says. A paper describing his findings has been accepted by Emerging Infectious Diseases, says Piarroux.