Research in Bangladesh has found that filtering contaminated water through old saris is a simple but effective way of purifying it of organisms that cause cholera. Scientists say using cloth as a sieve may be useful against a variety of water-borne diseases worldwide.
Boiling is the best way to sanitize water because it kills disease-causing organisms. But in rural Bangladesh, firewood is scarce and expensive, so U.S. and Bangla researchers have come up with another disinfecting method that everyone can do easily and cheaply.
They report in the Proceedings of the U.S. National Academy of Sciences that straining river or pond water through at least four layers of old cotton sari cloth can significantly cut the incidence of cholera, a water-borne disease that causes diarrhea.
At the University of Maryland's Center for Marine Biotechnology, scientist Anwar Huq says the porous fabric traps tiny aquatic organisms called plankton to which cholera bacteria attach.
"The beauty of this method is it is simple, does not require formal training, and it is cheap, in fact without additional cost to the villagers," he explained. "Those old saris when they cannot be used any longer for wearing are used for this filtration. The biggest advantage is it is readily available in each and every household in Bangladesh regardless of how unprivileged they are."
Cholera continues to ravage developing countries. The World Health Organization recorded 184,000 cases in 2001 with 2,700 deaths, although the researchers say the disease is grossly underreported.
To determine how well sari cloth filtration combats infection, Mr. Huq and others from the University of Maryland, the Johns Hopkins University in Baltimore and the International Center for Diarrheal Disease Research in Dhaka conducted tests in Bangladesh villages over 18 months. They compared sari cotton to nylon cloth. Villagers who used either material lowered their rate of new cholera cases by half compared to the historic average.
The scientists included nylon in the tests because of its successful use in the campaign to eradicate guinea worm disease in Africa. But they recommend sari fabric and similar cottons because it is cheaper and easier to get than nylon. The scientists say older cloth is best because repeated washings soften and loosen the threads, reducing the pore size.
Mr. Huq says his group is also studying whether the simple filtration method also works against other water-borne diseases in Bangladesh. "In general if the organisms are attached to something and this particle is large enough, [and] can be retained by this kind of filtration system, then that particular disease can be reduced," he said.
The University of Maryland scientist says he got the idea using sari cloth as a sieve from his days as a youth in Bangladesh, when he saw the method used for collecting insects from sugar and molasses.