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NLM AIDSLINE
ORIGINS OF AIDS
Essex M; Dept. of Cancer Biology, Harvard Sch. of Public Health,
May 30, 1989
AIDS: Etiology, Diagnosis, Treatment, and Prevention. Second Edition.

AIDS was first described as a new and distinct clinical entity in 1981. The first cases were recognized because of unusual clustering of diseases such as Kaposi's sarcoma and Pneumocystis pneumonia in young homosexual men. The history of AIDS is summarized, including studies of the infectious etiology of AIDS, the origins of human retroviruses, the origins of HIV-1, the HIV-related retroviruses of monkeys, and HIV-2. Although simian immunodeficiency virus (SIV) and HIV-2 clearly are highly related, and each is more than 50% related to HIV-1, none of these viruses is very closely related to other retroviruses. More distant relatives include lentiviruses such as equine infectious anemia and visna, which share only a small amount of homology with the HIVs, and HTLV-I and II, which share even less genomic homology but more biologic characteristics, such as T4 lymphocyte tropism. It seems less likely that SIV in African green monkeys was the immediate precursor of HIV-1, but highly likely that it did give rise to HIV-2. A more logical hypothesis might be that HIV-1 moved into humans from a precursor virus in another species yet to be identified. Similarly, the postulated evolutionary virus progenitor that gave rise to both SIV and HIV-1 has not been identified. (59 Refs)

Acquired Immunodeficiency Syndrome/*MICROBIOLOGY/TRANSMISSION Animal Haplorhini Human HIV-1/*PATHOGENICITY HIV-2/*PATHOGENICITY Monkey Diseases/MICROBIOLOGY Retroviridae Infections/MICROBIOLOGY/VETERINARY Risk Factors SIV/PATHOGENICITY MONOGRAPH REVIEW REVIEW, TUTORIAL

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