for National Geographic News
Chimpanzees living in dense jungles in Africa have been confirmed as the probable source of the HIV virus which caused the human AIDS pandemic.
Researchers have identified simian immunodeficiency virus (SIV) in wild apes for the first time. The virus, which at some point jumped to humans as human immunodeficiency virus (HIV), has been found in chimpanzees in Cameroon, west-central Africa. (Cameroon map and profile)
Scientists have long suspected that HIV had its in origins in wild chimp populations. But previously SIV had been found only in some captive chimps.
The discovery in wild chimps was made by an international research team, which detected SIV antibodies in chimpanzee feces gathered from forests.
The virus was found in chimpanzees in southeastern Cameroon, where SIV infection rates were as high as 35 percent in some chimp populations.
Further genetic analysis linked these chimps to the source of the main strain of HIV-1, the most prevalent form of HIV. The team's findings are to be published tomorrow in the journal Science.
The Cameroonian chimps showed a diversity of SIV strains, with some twice as similar to human HIV strains as any found in captive apes, says study team member Beatrice Hahn, a professor of medicine at the University of Alabama at Birmingham.
"Two clusters [of SIV strains] were very closely related to human strains," she added.
These human strains belong to the M group of HIV-1, the group which has spread among humans worldwide.
The SIV clusters were restricted to communities of the chimpanzee subspecies Pan troglodytes troglodytes.
Origins of AIDS
The team says the findings provide the clearest picture yet of the 70-year-old origins of the current human AIDS pandemic.
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