Genetics and Evolution of Infectious Diseases

Abstract

This chapter deals with the origin and emergence of AIDS and briefly explains how HIV is closely related to simian immunodeficiency viruses (SIV) from nonhuman primates. The discovery of the first SIV, the SIVs in African nonhuman primates, pathogenicity of SIVs in their natural hosts and evolution and phylogeny of SIVs are explained. It explains how the HIV-1 is derived from SIVs circulating among African apes and reviews how SIVs from chimpanzees and gorillas are the ancestors of HIV-1 in humans. The ongoing exposure of humans to a large diversity of SIVs, exposures to SIV-infected primates, SIV prevalences and cross-species transmissions, viral adaptation and how human factors play a major role in the epidemic spread of a new virus, especially among viruses that are transmitted by blood or sexual contacts, as it is the case for HIV are discussed. It reviews how the ongoing cross-species transmissions from other retroviruses from primates to humans, the ongoing transmissions of SFV and STLV which emphasizes on the risk for potential emergence of a new SIV into the human population. The current HIV-1 epidemic provides evidence for the extraordinary impact that can result from a single primate lentiviral zoonotic transmission event. It concludes that while more insights are gained about the origin of the HIV-1 and HIV-2 viruses, there are some important questions concerning pathogenicity and epidemic spread of certain HIV/SIV variants which needs to be further elucidated.