Gajdusek, pronounced GUY-da-shek, won the 1976 Nobel Prize for medicine for theorizing the existence of ``slow viruses'' that lie dormant for a long time before attacking the body. He was recognized for his work on a class of diseases - including mad cow disease, Creutzfield-Jakob disease, kuru and scrapie - that affect the brain.
Gajdusek retired Monday from his job as chief of the Laboratory for Central Nervous System Studies at the National Institutes of Health in Bethesda. He had been on leave since his arrest April 4 and remains free on $350,000 bail.
Frederick County State's Attorney Scott Rolle said he negotiated the plea agreement because he wanted to make sure Gajdusek spent some time in jail.
``I don't think it's a light sentence,'' he said. ``For a 73-year-old man to go to jail for a year is going to be a substantial period of the rest of his life.''
Under the plea agreement, Gajdusek is prohibited from having unsupervised contact with minors after his release. He will be on probation for five years after his release but will be free to leave the country.
Rolle said he expected the scientist to move to London after serving his sentence.
``We can't monitor him overseas. My goal was to make sure he was out of my county and out of the United States,'' he said.
Defense attorney Mark J. Hulkower said the sentence would allow Gajdusek to resume his studies in another country, if he wishes.
``We believe it's an appropriate disposition of the case,'' Hulkower said.
The victim, now 24, would have testified at a trial but was reluctant to see Gajdusek jailed, Rolle said. He said three other victims have returned to Micronesia. Another victim, a former neighbor of Gajdusek, is in prison for a serious crime, Rolle said. The prosecutor wouldn't elaborate on that case.
During the hearing, Gajdusek answered simply, ``Yes, I am,'' when Frederick County Circuit Judge G. Edward Dwyer asked whether he was pleading guilty because he was indeed guilty. He had no comment following the hearing.
Gajdusek arrived and left the courtroom surrounded by more than a dozen supporters, including fellow scientists and some of his adopted children.
Gajdusek contended he brought the children to this country to educate them. When he accepted the 1976 Nobel Prize with eight boys in tow, he promised to use the $80,000 prize money to send them to college.
Some of the boys, who called him ``Father,'' went on to prestigious careers. One is director of planning and budget for the Micronesian state of Yap. Another is a doctor there.
Those men and a number of prominent scientists supported Gajdusek throughout the investigation. Fellow Nobel laureate and prominent AIDS researcher Robert Gallo contributed to his bail fund.
One of Gajdusek's colleagues, Paul Brown, has alleged the charges resulted from a law enforcement ``setup'' initiated by people who misunderstood Gajdusek's research.
``In the fullness of time, the entire story will unravel and a lot of additional information will be made available,'' Brown said after Tuesday's hearing.
The FBI said last year its case against Gajdusek grew out of an investigation of child pornography on the Internet, where investigators found references to his journals.
The published journals of Gajdusek's research trips to New Guinea, Micronesia and other Polynesian islands contain descriptions and musings about sex between men and boys.
Brown has said visitors to these islands were invited to participate in the local customs, both culinary and sexual, and that to decline would be inappropriate.