- CKCLv 51 decade agoFavorite Answer
Simian immunodeficiency virus (SIV) is a retrovirus that is found, in numerous strains, in primates; the specific strains infecting humans are HIV-1 and HIV-2, the viruses that cause AIDS.
The origin of HIV is now generally attributed to SIV from African primates. HIV-2 is most closely related to SIVsm, the SIV strain that primarily infects Sooty Mangabeys, while HIV-1 is closely related to the chimpanzee strain of SIV, designated SIVcpz. The most likely route of transmission of HIV-1 to humans involves contact with the blood of chimps that are often hunted for bushmeat in Africa.