This is the VOA Special English Health Report.

There are low-cost vaccines, taken by mouth, that can protect against cholera. The vaccine is commonly provided to international travelers, but not to communities that suffer cholera epidemics. There are questions about how effective it would be as a control measure.

New findings suggest that it would be highly effective. These are based on the predictions of a computer model. Researchers say the model shows that the vaccine could reduce new cases in high-risk areas by ninety percent. And they say only half the population would have to take it once every two years.

Cholera is a serious bacterial disease found mainly in developing countries. People can get it from water or food that comes in contact with human waste. The intestinal infection causes a loss of fluids.

Cholera is treated by drinking an oral rehydration solution which replaces lost fluids and salts. In the most severe cases, fluids are injected into the body. Without treatment, it usually kills people within eighteen hours to several days. Estimates are that the disease kills at least one hundred thousand people a year.

Ira Longini at the Fred Hutchinson Cancer Research Center in Seattle, Washington, led the new work. A team from the United States, South Korea and Bangladesh based it on a large study of oral cholera vaccine.

The study took place between nineteen eighty-four and nineteen eighty-nine. It involved two hundred thousand women and children in rural Bangladesh.

The team developed the computer model based on the results of the study. The model showed that if fifty percent of a high-risk community is vaccinated, many unvaccinated people also would be protected.

The researchers say the number of new infections could drop below one in one thousand people in the unvaccinated population. This would be the result of what is known as "herd protection."

The idea is that vaccinated people would not become infected, so they would not create conditions for spreading the disease. Unvaccinated people then would have a better chance of avoiding it.

Ira Longini says researchers are very good at predicting where cholera is likely to spread. So vaccination efforts could target those areas. The findings appear in the medical journal published by the Public Library of Science and available free of charge at plos.org.

And that's the VOA Special English Health Report, written by Caty Weaver. For more health news, along with transcripts and MP3 files of our reports, go to WWW.51VOA.COM. I'm Steve Ember.