Page last updated at 23:42 GMT, Monday, 10 November 2008

Satellites map cholera outbreaks

Whole villages seek refuge on higher land from Bangladesh's floods
Cholera epidemics can follow flooding

Researchers have developed a system for predicting cholera outbreaks using satellite monitoring of marine environments.

They show cholera outbreaks follow seasonal increases in sea temperature.

This could provide an early warning system for India and Bangladesh where cholera epidemics occur regularly.

Tiny animals which increase in number with sea temperature rise bring the cholera pathogen into the drinking water supply.

Phytoplankton

The satellites picked up sea temperature changes in the Bay of Bengal and measured the amount of phytoplankton, the tiny marine plants which feed ocean ecosystems.

They found cholera outbreaks in Kolkata (Calcutta) in India and Matlab in Bangladesh occurred soon after seasonal rises in sea temperature which in turn lead to increases in phytoplankton densities.

Professor Rita Colwell, from the Institute for Advanced Computer Studies at the University of Maryland has been studying cholera outbreaks for over 30 years. She says the satellite monitoring holds the key to preventing cholera epidemics.

"We can use the current data taken from the satellites to predict when the onset of cholera epidemics will occur, it allows public health authorities to pinpoint exactly when to allocate resources or implement warnings about drinking the water," she said.

Copepods

Cholera can spread quickly from person to person
Children queue to collect clean drinking water following flooding in Bangladesh

The cholera pathogen lives naturally in the gut of a zooplankton species - tiny marine animals called copepods, these feed on the phytoplankton.

When sea levels rise copepods find their way into the water supply in low lying parts of Bangladesh and India.

Professor Colwell says using simple cloth filters to remove the copepods can dramatically reduce the incidence of cholera.

"We found we could reduce cholera 40-50% by just filtering out the plankton," she said.

The researchers hope to soon be able to predict cholera outbreaks weeks or even months before they occur by using satellite monitoring, looking at what is happening further out to sea, examining the timings of ocean currents and associated growths in plankton numbers.



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