Ulcer-causing bacteria found in water.

After much controversy, physicians and researchers are beginning to accept that the bacterium Helicobacter pylori causes most stomach ulcers. They're now turning their attention to why so many people, more than 30 percent of the U.S. population, seem to harbor this troublesome microbe, which also appears to cause stomach cancer.

Researchers from the Massachusetts Institute of Technology say an answer may lie in contaminated drinking water. They obtained water samples from Narino, Colombia, an area with one of the world's highest prevalences of ulcers and gastric cancer and where H. pylori infects more than 90 percent of the population. David Schauer and his colleagues analyzed the water for pieces of DNA belonging to the bacterium. "No one had ever gone out and looked at environmental water samples," he notes.

Some of the samples indeed test positive for H. pylori, reports Schauer. This summer, his group hopes to examine samples collected in the United States. Identifying where the bacterium normally resides, Schauer comments, "may tell us a lot about how one can actually prevent the disease."