A complex of causes -- including global warming -- may be making worse the threat of cholera outbreaks.

"The cholera bug lives on tiny sea crustaceans in the Bay of Bengal. The sea critters thrive in these tropical conditions, feeding on blooming phytoplankton. So too does the cholera bacterium.

It is the increasing flow of rivers carrying agricultural nutrients into oceans that promote phytoplankton, and by extension, cholera bugs in the environment, according to a new study published in The American Journal of Tropical Medicine and Hygiene.

Some had suggested a direct role for global warming, based on a paradoxical observation: In the Bay of Bengal, rising sea surface temperatures -- a key end point of climate change -- have been linked to a thriving population of phytoplankton. Everywhere else in the world, warmer water causes phytoplankton to die out."