The dispute between scientists over the origins of the cholera epidemic in Haiti has been further fuelled by two conflicting reports.
One report published argues that the epidemic is directly traceable to UN peacekeepers, while the second challenges such conclusions and blames environmental factors for the outbreak.
The epidemic, which is currently the world’s largest began in October 2010, following a massive earthquake that devastated the country earlier that year. By July 2011, cholera had spread, infecting one person a minute on average, the report says.
More than 8,200 people have died and 670,000 others have had the disease, according to data from the Haiti Ministry for Public Health and Population. But the search for the source of the ongoing epidemic has exercised scientists because cholera had never been reported in Haiti for more than a century.
The waterborne diarrhoeal disease, which is caused by the bacterium Vibrio cholerae, is prevalent in Sub-Saharan Africa, Latin America and South Asia, affecting more than three million people every year.
A study published by Yale’s Law School and School of Public Health, and the Haitian Association of Environmental Law — ‘Peacekeeping without Accountability’ — maintains that Nepalese UN peacekeeping troops introduced the disease to the country and urges the organisation to take responsibility for the outbreak. Previous studies established that the Haitian cholera strain matches the one in Nepal, it says.
Further evidence for the epidemic having a South Asian origin is that it started two kilometres from the UN base in Méyè, from where contaminated sewage leaked into a tributary of one of Haiti’s main water sources, the Artibonite River, according to most studies so far.
In addition, there was a cholera outbreak in Nepal in July to August 2010, the Nepalese soldiers arrived in Haiti between 8-21 October, and the first reported hospitalisation in Haiti due to cholera was on 19 October.
But another study, published in The American Journal of Tropical Medicine and Hygiene, argues against there being one source of the epidemic and points to the existence of two strains in Haiti: the O1 variant resembling V. cholerae populations from South Asia and Africa, and a local strain.
The researchers postulate that cholera bacteria, dormant in river waters, multiplied due to the chance occurrence of optimal environmental conditions around the time of the outbreak: warm temperatures and heavy rainfall followed by flooding. The destruction by the earthquake of water and sanitation infrastructure would have helped spread the disease.
Source: María Elena Hurtado | SciDev.Net