OSLO, Norway - Nobel Prize-winning medical researcher Dr. D. Carleton Gajdusek, who studied brain diseases and infections that lie dormant for years before attacking the body, has died, his biographer said Tuesday. Gajdusek was 85.

The American scientist, who spent about two decades at the National Institutes of Health, shared the 1976 Nobel Prize in medicine for his work on so-called "slow viruses." The infectious agents include one implicated in mad-cow disease.

His biographer, Dr. Robert Klitzman of Columbia University in New York, told The Associated Press that Gajdusek, was found dead Dec. 12 at a hotel in Tromsoe, Norway, where the laureate spent several months a year. Klitzman said he did not know the cause of death but added that Gajdusek suffered from congestive heart failure.

Gajdusek, born Sept. 9, 1923, in Yonkers, New York, graduated in 1943 from the University of Rochester in upstate New York. He graduated from medical school at Harvard in 1946 and did postgraduate work at the California Institute of Technology, among other places.

Gajdusek spent years studying a unique group of brain diseases in the South Pacific, including one that attacked a primitive tribe in the highlands of New Guinea. The disease, called Kuru, quickly destroys brain tissue and within six to 12 months leads to the death of the patient.

Gajdusek found that Kuru was spread through the tribe's practice of cannibalism.

His research trips to various Pacific islands also contained descriptions of the sexual customs of those cultures, especially sexual relations between adult men and adolescent boys.

His research triumphs were marred by a child molestation case when, in 1997, he pleaded guilty to molesting a teenage boy, one of dozens of children he had brought from the Pacific islands to live with him in Middletown, Maryland.

Prosecutors at the time said Gajdusek had brought home 56 boys from research trips. He said he brought the children home to educate them.

After serving a one-year jail term in Maryland, Gajdusek left the United States and spent his time in Paris, Amsterdam and Tromsoe, Klitzman said by telephone from New York.