earthquakes

To stop cholera in Haiti, vaccinate some—not all

U. FLORIDA (US) — Vaccinating less than half the population could shut down the two-year cholera epidemic that has claimed thousands of lives in Haiti since the 2010 earthquake.

The Centers for Disease Control and Prevention has been skeptical about the effectiveness of vaccination against cholera in this setting and has instead emphasized cleaning up the water supply and improving sanitation as the best ways to check the spread of the disease.

Researchers say that vaccinating 46 percent of Haitians could arrest the spread of cholera. They also noted the importance of using mathematical models to target immunization campaigns to gain the best results from the effort involved in vaccination in resource-poor settings.

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“You don’t have to immunize everybody. Even if we could get an immunization rate in the range of 40 to 50 percent, it should be possible to control recurrent cholera outbreaks,” says J. Glenn Morris of the Emerging Pathogens Institute at the University of Florida.

“That should be enough to tilt things in your favor so that you can start getting control of the disease in these areas, to where, hopefully, rates of transmission will slow and numbers of cases will gradually die off.”

Morris points to the “herd immunity” concept—which proposes that immunizing a significant portion of a population breaks a chain of infection—in support of the efficacy of less than universal vaccination.
Hundreds of thousands of Haitians have been infected since a catastrophic magnitude-7.0 earthquake occurred near Port-au-Prince three years ago.

Published in the journal Scientific Reports, the study by Morris and Zindoga Mukandavire is the latest contribution in what has been more than two years of efforts to combat cholera in Haiti. At the beginning of the epidemic the university sent thousands of oral rehydration packets to Haiti.

University of Florida researchers also have honed a molecular fingerprinting technique that helps scientists determine whether the disease is spreading from the contamination of food and water or being transmitted from person to person—and now have a permanent research laboratory in Haiti, providing ongoing monitoring of the epidemic.

Cholera is an infection of the small intestine that causes dehydration, abdominal cramps, and diarrhea. It can be fatal if untreated. It is most commonly spread through contaminated drinking water.

There also has been a dispute over the source of the cholera outbreak in Haiti after a century-long absence of the disease in the country. The latest work relies on a mathematical model that advances previous analyses by refining the way environmental sources of the bacterium that causes cholera are factored into calculations.

Source: University of Florida

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