(Agencies)
Updated: 2007-10-30 10:22

The study was published in the journal Proceedings of the National Academy of Sciences.

The path the virus traveled as it jumped from nation to nation has long been debated by scientists.

The University of Miami's Dr. Arthur Pitchenik, a co-author of the study, had seen Haitian immigrants in Miami as early as 1979 with a mystery illness that turned out to be AIDS. He knew the government long had stored some of their blood samples.

The researchers analyzed samples from five of these Haitian immigrants dating from 1982 and 1983. They also looked at genetic data from 117 more early AIDS patients from around the world.

This genetic analysis allowed the scientists to calibrate the molecular clock of the strain of HIV that has spread most widely, and calculated when it arrived first in Haiti from Africa and then in the United States.

The researchers virtually ruled out the possibility that HIV had come directly to the United States from Africa, setting a 99.8 percent probability that Haiti was the steppingstone.

"I think that it gives us more clear insight into the history of it (the AIDS epidemic) and what path the virus took -- and hard objective evidence, not just armchair thinking," Pitchenik said in a telephone interview.

Studies suggest the virus first entered the human population in about 1930 in central Africa, probably when people slaughtered infected chimpanzees for meat. AIDS has killed more than 25 million people and about 40 million others are infected with HIV.

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