October 17, 2012 | 10:41 am | Print
By Renaud Piarroux
On Oct. 21, 2010, a cholera epidemic began in Haiti, an area which had never been struck by this terrible disease.
Two years later, more than 600,000 new cases have been recorded and more than 7,500 people have died. The causative agent is a strain of Vibrio cholerae closely related to those which provoked an outbreak in Nepal in 2010. The genetic link is so narrow that it is now estimated that the clone responsible for the epidemic in Haiti has diverged from its Nepalese ancestor since 2009 or early 2010.
The conditions under which this bacterium was imported into Haiti are partially elucidated. All epidemiological investigations traced the origin of the epidemic to Meye, a village close to a base of United Nations peacekeepers where a contingent of soldiers had just arrived from Nepal.
Even a panel of scientists appointed by the UN acknowledged that “the evidence overwhelmingly supports the conclusion that the source of the cholera outbreak was due Haiti to contamination of the Meye Tributary of the Artibonite River with a pathogenic strain of current South Asian Vibrio cholerae as a result of human activity.”
The cholera epidemic is therefore not the consequence of the “perfect storm” described by Rita Colwell, a renowned expert on cholera. For this scientist, a “perfect storm” of environmental circumstances in 2010 enabled the bacteria to surface, as the impoverished country was hit by a massive earthquake, a hurricane and a “very hot summer season.”
In reality, the epidemic started in an area spared by the earthquake, following a summer which was not especially hot and, last but not least, at the time Hurricane Tomas stroke the country, thousands of cholera cases and hundreds of deaths were already recorded.
A mystery remains to be solved, a mystery provoking controversy in the scientific community. What role did Haiti’s environment play in this epidemic?
What was noteworthy about the cholera epidemic in Haiti was that it presented an original epidemiological pattern during its early days, characterized by the simultaneous contamination of thousands of people living near the Artibonite River and working in the rice fields irrigated by canals coming from the river.
In an epidemiological study of Haiti’s cholera epidemic that we published in 2011, we showed that, within only a few days, over 10,000 people were infected along the lower Artibonite River. At that time, we had concluded that the river and its tributary the River Meye played the role of the vector carrying cholera from Meye to rice fields in the Artibonite delta. Currently, no one disputes this assertion.
However, a question remains on the multiplication of the organism in the Artibonite water: did the nature of the Artibonite River turn a limited contamination of water by human waste into a major health disaster? UN officials, who always denied the occurrence of cholera cases in the Nepalese contingent, could easily hide behind an unfortunate combination of circumstances: a few thousand bacteria inadvertently dropped in the course of a tributary of the Artibonite proliferated until they reached such a level that the river could contaminate thousands of people, killing hundreds within a few days.
It is clear that the Artibonite River and its canals played a role in the spread of cholera. But we are convinced that, without any sick people among peacekeepers of the United Nations, without the formation of a reservoir of bacteria in the septic tanks of the military camp and without waste discharge into the waters of a river, the epidemic could not have developed so brutally.
If the conjunction of favorable weather conditions with a limited contamination of the water by an asymptomatic carrier would be enough to provoke such a violent outbreak of cholera, there is no doubt that the burden of cholera would be much higher than it is currently in the world. In such a case, very few people would escape from cholera epidemics in developing countries.
Even if the Artibonite River, because it had been heavily contaminated with fecal wastes, played a role in cholera in Haiti, should we conclude that this river will remain a permanent reservoir of germs? Will its water systematically depart epidemics whenever the temperature rises and the rain falls? Nothing can assert these dire predictions at this stage.
Now that we are away from the large outbreaks which occurred in 2010 and 2011, it seems that, in Haiti’s watery environment, the cholera clone that provoked the epidemic is currently overwhelmed by other bacteria, including Vibrio cholerae that do not produce toxin and that are not able to provoke deadly epidemics in humans.
Studies are underway to confirm such an observation, but this brings a message of hope with which I would like to end this article: if the environment actually was an auxiliary at the onset of this epidemic, it would seem to be not permissive enough to sustainably host a large amount of the epidemic strain that was imported in 2010.
This enhances our hope of getting rid of cholera in Haiti, if increasing pressure is applied on current outbreaks, particularly on the often neglected outbreaks affecting inhabitants living in remote villages.
Haiti is not the first island territory to have been affected by cholera epidemic; others, like Madagascar, got rid of cholera after experiencing severe outbreaks in the early 21st century.
Hopefully everything will be done in order for this to happen in Haiti as well.
Dr Renaud Piarroux is an epidemiologist, Professor of Parasitology at the University of the Mediterranee (Aix-Marseille II) in France and an expert on cholera.
Note: the opinions expressed in Caribbean Journal Op-Eds are those of the author and do not necessarily reflect the views of the Caribbean Journal.