Strange though it might seem given the billions spent on HIV research since the early 1980s, it is only this week that we have finally found out exactly where the virus came from. HIV-1 was first found in western central Africa and researchers have always suspected that the virus passed to humans from chimpanzees. But so few samples of the simian immunodeficiency virus (SIV, the chimp cousin of HIV) were available that it was impossible to pin down the origin of the disease precisely.
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