Cholera continues to affect the developing world, killing thousands each year and infecting more than 10 times that many. Simply bringing water to a boil can kill the bacterium responsible for the disease, but fuel is often scarce in cholera endemic countries. Now the results of a three-year-long study published online this week by the Proceedings of the National Academy of Sciences offer hope for further combating the disease. Researchers report that using cloth salvaged from old saris to filter drinking water from rivers and ponds has halved the number of cholera cases in rural Bangladesh.

Previous laboratory studies had shown that tainted surface water was visibly clearer after being poured through a folded piece of sari cloth. Because the cholera bacterium associates with plankton, Rita Colwell of the University of Maryland Biotechnology Institute and the National Science Foundation and her colleagues posited that if the tiny aquatic organisms were removed from water used for household purposes, the occurrence of cholera would be reduced. To test their hypothesis, the scientists carried out a three-year study involving nearly 133,000 people in 65 villages in Matlab, Bangladesh. The team taught one group of participants to filter drinking water using typical sari cloth folded four times and provided a second group with premade 150-micron nylon filters. A third group acted as a control. According to the report, villages using either filtration method experienced a significant reduction in the number of new cholera cases as compared to the control group. The villages employing saris, in particular, had a disease rate that was half that of villages using unfiltered water. The saris, the scientists note, also have the added benefits of being "much less expensive, very effective, and readily available to all villagers in Bangladesh." The authors conclude that their findings "suggest that a simple solution to a global problem can be achieved when the ecological basis of the disease transmission and its reservoir are known."