Symptoms

He first went to the clinic with symptoms of sickle cell anemia, a blood disease common among Africans in which malformed red blood cells clump together.

Doctors kept samples of the blood of man and the team carefully analyzed Ho. After studying several samples from Africa, that was the only showing being infected with HIV, he said.

By using well-established genetic methods for determining dates, the team determined that the virus could not have existed many years before 1959. "This finding also refutes the suggestion that the subtype B HIV-1 was responsible for AIDS-like syndromes that began in the 1930s in several European populations," they wrote in a report in the journal Nature, also published their work this week.

Some researchers supported the hypothesis that a sailor from Manchester, England, died of AIDS in 1959, but has not been proven. The researchers withdrew their initial conclusions after several years.