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First Rita Colwell revealed where the cholera bacterium hides between epidemics. Now she is inventing new ways to fight it.
LAST YEAR MICROBIOLOGIST RITA COLWELL WAS visiting a rural village in Bangladesh with a crew from a Maryland public television station. The crew asked Colwell to show them a new method she had devised for filtering plankton and bacteria from drinking water. The cameras focused on a woman standing at the edge of the local "tank"-a large pond that in one corner is used as a latrine and in the other as a source of drinking water. In traditional fashion, the woman bent down and dipped her clay bottle into the water. "After she collected the water, we poured it into a clear beaker and held it up to the sunlight," recalls Colwell. "You could see the brown discoloration, things swimming in it." Next Colwell asked the woman to collect water again, this time while holding a few layers of sari cloth over the mouth of the clear beaker.
When the sample was held up to the light, the water was practically clear. Minutes later the film crew, wanting some background footage, asked the woman to walk to the tank again, collect some more water, walk back to her home, and take a drink. She did as they asked, but stopped short of drinking the water. She explained through a translator that, having just seen the results of the simple experiment, she no longer wished to drink unfiltered water.
It was a simple demonstration, but a pivotal moment for Colwell. After years of studying Vibrio cholerae, a notorious bacterium that can contaminate unchlorinated water supplies and cause massive epidemics of sickness and death, she could see that one of her ideas to help prevent the disease just might work. For more than two decades Colwell has labored in the field and in the laboratory to tease out the ecology of this tiny microbe. Her discoveries have overturned some long-held notions about how V. cholerae travels the world, how it is transmitted to humans, and where it lurks in the years between outbreaks. She hopes to use these ecological lessons to prevent future outbreaks, or at least to blunt their impact. Her sari-cloth filter,...