Until recently, scientists thought that Vibrio cholera, the bacterium that causes the disease, lives only a few days outside the human intestine. Colwell's work makes it clear that cholera is more complicated and durable than experts thought, but it also offers clues as to how the bacteria can be traced. Her research team takes samples from the sea and from fresh water in Peru. They thought it was person to person, but it is much more complicated than that. During the rainy season, plankton and bacteria are carried up rivers from the sea, contaminating the water supply.
People drink the water, get sick and recontaminate their water.
The disease gains momentum. Since sewage in poorer countries flows back into the ocean, there is an endless supply of the bacteria in sea water, continuing the cycle. Water is going to be the most important resource in the next century. Wendy Marston is a health and science writer who lives in New York.