Simian immunodeficiency virus

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.
See more at Wikipedia.org...

Virus /vi·rus/ [L.] a minute infectious agent which, with certain exceptions, is not resolved by the light microscope, lacks independent metabolism [more]Simian immunodeficiency virus - Community and Resources