Indian encephalitis is traced to measles.

Four outbreaks of encephalitis in India between 1995 and 1998 have been linked to a strange form of measles.

Although encephalitis is known to be a complication that occasionally follows measles, none of the ill children had a rash, so doctors didn't suspect measles, says epidemiologist Niteen S. Wairagkar of the National Institute of Virology in Pune.

Wairagkar and his team traced the cases of 329 children under age 16 who were hospitalized with high fever, vomiting, neck rigidity, paralysis, and, in some cases, coma. Of these children, at least 150 died, most within a day of hospitalization, he reports. Blood samples from 91 of the sick children revealed active measles in 52 and ruled out several other possible causes.

Indian researchers are puzzled by the disease, which cropped up in children living in four distinct regions hundreds of miles apart. "The story is not complete yet," Wairagkar says. While many Indian children receive vaccinations for measles, no immunization data were available on these children, he says.

"We are now doing genetic studies on this [measles] virus," he says. "It could be a variant [form of measles]. We don't know."

The distance between outbreaks suggests that the virus is widespread in India and that physicians may not recognize the disease as measles. The researchers have posted public-health alerts.