Lecturer warns of global warming's effect on cholera

A person can be completely healthy, but after drinking cholera-infected water, they could be dead within 24 hours. The bacteria can cause vomiting and severe diarrhea, forcing four gallons of fluid out of the body in one day.

Treatment is simple and easy: rehydration. But the key is to prevent catching cholera in the first place, and the solutions don’t have to be high-tech water purification systems.

It can be as simple as a piece of cloth, said Rita Colwell, a professor at the University of Maryland who gave Monday night’s Presidential Lecture.

Colwell, also a professor at Johns Hopkins University’s Bloomberg School of Public Health and chairwoman of Canon U.S. Life Sciences, Inc. spoke in the University Theatre as part of the President’s Lecture Series. She has been studying cholera for years, trying to figure ways of predicting epidemics and discovering factors that influence outbreaks.

Cholera is caused by an infection of the intestine with the cholera bacteria, which is usually found in water contaminated by the feces of someone with cholera. The disease can spread quickly in areas with no sewage treatment or water sanitation.

In the United States, cholera has been essentially eliminated through modern sewage and water treatment plants, but parts of some continents, such Africa, Asia and Latin America, suffer through outbreaks every spring and fall.

These countries are undeveloped and impoverished. Water treatment plants are out of the question in places like Bangladesh where Colwell has been studying cholera, she said. These people get their water from rivers or man-made ponds in their backyards, not from pipes and faucets.

“They use one corner of the pond for their latrine,” Colwell said, “another for washing dishes and another for gathering drinking water. Obviously, the bacteria don’t stay put.”

Last September, 1,000 patients came in every day to the cholera hospital in Bangladesh, Colwell said. But everyone that ingests cholera doesn’t become overtaken by diarrhea and vomiting. Only 2 percent become severely ill, and 75 percent don’t show any symptoms at all, she said.

“Some (people) die, but most fortunately survive,” she said.

Cowell’s goal is to provide safe drinking water. Even though she and others have used intense chemistry to uncover the root cause of cholera – certain plankton carry the bacteria – the solution needs to be simple and easy for the villagers of Bangladesh.

“This is a very impoverished society,” she said. “The simplest solutions are the best.”

Cowell and her group found that a certain cloth — easily found in Bangladesh — could be used to filter drinking water. All they need to do is fold the cloth four or five times and run the water through it. The plankton cling to it, she said. After a three-year study, the results were encouraging, she said.

“We were able to reduce cholera by 50 percent,” she said.

Colwell said that cholera epidemics have gotten worse because of global warming and atmosphere changes.

“The disease depends upon interactions of weather, environment and disease,” she said.

Cholera epidemics occur in fall and spring months when water temperatures increase, Colwell said. The bacteria live year round but become dormant when the temperature falls below 59 degrees. When the temperature rises above that point, the cholera bacteria riding on plankton grow, causing more cases. Colwell has used satellites that detect ocean temperatures to foresee cholera outbreaks, and the predictions have been right on, she said.

“There’s a very distinct pattern that happens year after year,” she said.

When Colwell overlays a graph showing spikes in water temperatures with a graph of cholera cases for the same time period, the increases and decreases correlate. They even predicted the number of cases in Bangladesh for June in 2004. They predicted there would be 24 cases of cholera per 1,000 people that came into the hospital. The hospital reported 25, Colwell said.

After becoming keen in predicting cholera outbreaks and studying the trends for 45 years in Bangladesh, Colwell sees a close tie to global warming, she said. Cholera feeds on increasing water temperatures and rising sea levels. And America isn’t immune even though it’s not even close to third world. For the first time last year, Alaska and Seattle saw cases of food poisoning because of bacteria similar to cholera, Colwell said. Nine people died.

“The patterns of infectious diseases relates to environment,” she said. “I hope that we understand humans are just one species on this wonderful blue planet.”