Unlike HIV-1 and HIV-2 infections in humans. SIV infections in their natural hosts appear in many cases to be non-pathogenic. Extensive studies in sooty mangabeys have established that SIVsmm infection does not cause any disease in these animals, despite high levels of circulating virus. However, if this virus infects an Asian or Indian rhesus macaque. , the animal will develop simian AIDS (SAIDS).5
A recent study of SIVepz in Wild living chimpanzees suggests that infected chimpanzees experience an AIDS-like illness similar to HIV-1 infected humans. The later stages of SLV infection turn into SAIDS, much as HIV infection turns into AIDS.