Institut de recherche pour le développement (IRD), UMR145, Université de Montpellier-I, 911, avenue Agropolis, BP 64501, 34394 Montpellier cedex 05, France
Human immunodeficiency viruses (HIV) are the result of multiple viral cross-species transmissions from non-human primates to humans. SIVs from chimpanzees and gorillas from west central Africa have crossed the species barrier on at least four occasions leading to HIV-1 in humans. HIV-2 viruses result from at least eight independent transmissions of SIVs infecting sooty mangabeys from West Africa. These HIV variants have different virological and epidemiological histories. Some have remained restricted to a few cases of human infections, while others have spread worldwide, like HIV-1 group M affecting today more than 33 million people. Zoonotic emergence of new lentiviruses has to be considered given the prevalence of SIVs in some primate species, the increased contact between humans and wild primates through hunting and bushmeat preparation, and the socio-economic and demographic factors predisposing global expansion of viral infections.