June 1, 2011

Combating Cholera Outbreaks With New Computer Models

Researchers are focusing their attention on a computer model that would aid in predicting cholera outbreaks based on temperature increases and rainfall patterns.

Cholera is a potentially lethal diarrhea-causing bacteria that affects vulnerable populations, often without warning.

Scientists at the International Vaccine Institute in Seoul, South Korea, analyzed several years of past data in cholera-prone parts of Zanzibar, Tanzania, showing that when temperatures rose one degree Celsius, cholera cases were likely to double within four months.

Spreading through water and food contaminated with the bacterium Vibrio cholerae, cholera infection can take hold in less than a day and kills through dehydration caused by severe diarrhea. With such a short incubation time for the disease gives health officials gives health officials very short notice before people start to die from it, The Guardian reports.

An increase in rainfall, of even 6.7 ounces per month, forecast that a "substantial increase could be expected within two months," said the researchers in the June issue of the American Journal of Tropical Medicine and Hygiene.

Mohammad Ali of the International Vaccine Institute in Seoul and fellow researchers examined climate records and cholera outbreaks between 1997 and 2006 from the two main islands of Zanzibar off the coast of Tanzania. The research revealed a strong correlation between higher temperatures and rainfall with cholera outbreaks several months later.

The work will be fed into a forecasting system that draws on local climate monitoring and rainfall patterns to warn of impending outbreaks. Ali explained that research was continuing in hopes of forecasting to other countries where cholera is rife, but in some regions climate records were too incomplete to verify the research.

As temperatures rise as a result of global warming, cholera is expected to become a more serious problem in countries that have historically been spared the disease.

Cholera epidemics are expected to also last longer as warmer weather patterns emerge. A cholera epidemic in Haiti that started in October 2010 after that country's deadly earthquake has killed 5,000 people and the Haitian government is preparing for fresh cholera outbreaks with the start of the rainy season, Reuters reports.

Cholera sickened more than 220,000 people around the world in 2009, killing almost 5,000 of them, according to the World Health Organization (WHO). The cholera bacteria reside in sea organisms called copepods. Rises in sea temperature lead to a proliferation of copepods, which in turn helps the cholera bacteria multiply.

"When temperature goes up, cholera bacteria in the ocean environment multiply ... Oceans meet ponds and rivers and then humans (get infected)," Ali explained to Reuters.

Peter Hotez of the American Society of Tropical Medicine and Hygiene urges fresh ideas about combating cholera. "This paper implicates that global warming and climate change may have a key role, it also means we need new tools to combat cholera epidemics," Hotez told Reuters report Tan Ee Lyn by telephone.

"In the past, the dogma has been there's no time to vaccinate because the epidemic will burn itself out. But now with protracted epidemics, we should stockpile the cholera vaccine," Hotez added.


Image Caption: Scanning electron microscope image of Vibrio cholerae bacteria, which infect the digestive system.


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