With saris, US scientists take on cholera

Lab studies (electron microscopy) prove that old saris folded eight times and placed over a pot of water work as a mesh, filtering over 99 per cent of vibrio cholerae, the bacteria that causes the disease, attached to the plankton, enough to prevent the ingestion of infectious levels of the bacteria while gulping down a glass of water.

NSF spent three years, studying a control group of 1,33,000 people in 65 villages across Matlab in Bangladesh to see how using sari filters helps fight cholera.

‘‘Cholera incidence was reduced by over 50 per cent in villages that used sari filters,’’ says NSF director Rita Colwell, who is here to attend the ongoing Indian Science Congress in Chandigarh.

Colwell adds that NSF scientists, who have been studying cholera cases across continents and seasons, have found parallel patterns. Armed with data, she shows how there is a huge chain linking cholera outbreaks from a saltwater bay in Maryland to microorganisms in the Indian Ocean and rain in South America. She says this points to a possibility for an early warning system for cholera.

‘‘We are poised on the threshold of prediction,’’ says Colwell. ‘‘Examining these links, we hope to move from understanding to prediction and, finally, to prevention.’’

Colwell and her team found that the ocean is a reservoir of vibrio cholerae after identifying samples from Chesapeake Bay. They also saw that the population of native cholerae in the bay fluctuates with the seasons as it does across the globe.

After analysing satellite data on global sea surface temperature and height, they came to find out that cholera outbreaks are seasonal. ‘‘Using remote sensing data,’’ explains Colwell, ‘‘we found that cholera outbreaks in Bangladesh occur shortly after the sea surface temperature and height reach their zenith, which happens twice a year.’’

A similar pattern is seen miles away in South America. Studies in coastal Peru show a co-relation between the increase in sea surface temperature and annual outbreaks of cholera.

Satellite data suggests that certain temperature patterns unfold in the Himalayas six months before the incidence of cholera rises along the South Asian coast. ‘‘It is a research direction on the cusp of being explored,’’ says Colwell in a paper on using remote sensing in the Bay of Bengal to predict cholera epidemics which was presented at the Science Congress.