Satellites to predict cholera outbreaks

Rita Colwell has saved hundreds, possibly even thousands, of lives using cotton saris and satellites.

Colwell, a distinguished university professor, has conducted research on cholera for 30 years and has recently been working on using satellite data to create a model to predict cholera outbreaks four to six weeks before they happen.

"It allows the opportunity to do preemptive medicine," Colwell said. "If you are able to predict very precisely, people listen."

Cholera, an infection that can kill a person from severe dehydration within 48 hours, is a prevalent public health problem in developing countries. The infection is caused by Vibrio cholerae, a naturally occurring marine organism. When people drink contaminated water from rivers and streams, they ingest the organism.

In developed countries such as the United States, water is filtered and chlorinated, killing any V. cholerae in drinking water. Though developing countries usually do not have the means to build a complex filtration system, it turns out they do not need one - they can use simple saris.

"It is so simple; it doesn't cost a penny," said Anwar Huq, a resident associate professor and one of Colwell's colleagues. "The cheapest kind work best."

A sari, a staple clothing item in Bangladesh, where Colwell's research took place, can be folded to make a crude filtration system. V. cholerae attach themselves to copepods, small crustaceans found in nearly every aquatic habitat. Even though the saris are just cotton cloth, they create a small mesh when folded. When the water is poured through a sari, the copepods - and subsequently the V. cholerae - are filtered out of the water. Through this simple measure, cholera cases were reduced by 50 percent, Colwell said.

However, Colwell said she thinks cholera could be further reduced by an early warning system.

Colwell and her team use satellites to collect data on the temperature, salinity and amount of chlorophyll - a value highly linked to the level of algae - in bodies of water. If there is a lot of algae, the zooplankton population will spike, because zooplankton feed on algae. When the zooplankton population increases, so does the V. cholerae population.

Colwell and other scientists are working to develop a model to effectively use the satellite images to predict when and where cholera outbreaks will strike.

"If we develop a model, we should be able to predict cholera all over the world," Huq said.

Cholera organisms are seasonal and rely on the perfect blend of temperature, salinity and nutrition. Huq said the ideal temperature for cholera is around 77 degrees Fahrenheit. With global warming, more waters around the world are becoming warmer and more conducive to cholera outbreaks. The cholera organism is found in "virtually every estuary in the world," including the Chesapeake Bay, Colwell said, but usually does not multiply and reach numbers high enough to infect humans. If the climate changes, however, cholera outbreaks could happen in countries - including the United States - that have not seen a cholera outbreak in the past 100 years.

"During peak summer season in Ocean City, Md., if there is a report of a cholera outbreak, this is enough to create a huge impact on beachgoers," Huq said. "If we can predict, at least we can be careful."

Fuente: The Diamondback: Student newspaper University of Maryland
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