European and U.S. researchers report in the June 13 edition of the journal Science that they have traced the origins of HIV to two viruses found in monkeys in Africa that likely leapt from the animals to chimpanzees and finally to humans. The two viruses, found in the red-capped mangabeys and the greater spot-nosed monkeys in south-central Africa, likely entered the chimp population when chimps ate infected monkey meat and then combined to form the simian immunodeficiency virus. SIV was likely passed to humans on at least three occasions, mostly likely before 1930, through either the slaughter of chimps for meat or the eating of chimp meat, the researchers say. The study confirms other research suggesting that SIV was the root of the human AIDS pandemic, but it is the first to link SIV to other viral strains found in monkeys.
Researcher Frederic Bibollet-Ruche, of the University of Alabama, Birmingham, said three strains of HIV-1 now common in Africa likely were transmitted from chimps to humans decades ago and eventually mutated into the various strains of HIV-1 now infecting humans around the world. A second, less virulent HIV subtype, HIV-2, is believed to have been transmitted from West African sooty mangabeys directly to humans. HIV-2 infection is common only in West Africa, and humans infected with that virus tend to live much longer than those infected with HIV-1.