Acquired immunodeficiency syndrome, or AIDS, is the final, life-threatening stage of infection with any of the human immunodeficiency viruses (HIV-1, its many subtypes, or HIV-2), which are transmitted from person to person sexually (including via anal, oral, and vaginal intercourse, both heterosexually and homosexually), through contact with blood (mainly via equipment used to inject illicit drugs and, rarely, via medical uses of blood), and perinatally (from mother to fetus or newborn during pregnancy, labor, and delivery, or after birth through breast-feeding).
ORIGIN AND HISTORY
HIV-1 and HIV-2 both appear to have been transmitted to humans from primates in Central and West Africa, probably to hunters or processors of carcasses of primates consumed as food (referred to as "bush meat"). Beginning as simian viruses, they became human viruses once they achieved sustained transmission from person to person. This appears to have occurred at least four times in history: three times from chimpanzees (Pan troglodytes); (possibly in the 1930s), representing the three major strains of HIV-1, and once from sooty mangabeys, representing HIV-2. Social and technological changes in Africa resulted in transmission of HIV to larger and larger numbers of adults as roads were built and river transport developed, making travel to cities, with their better economic opportunities, far easier and more rapid. A silent heterosexual epidemic occurred and spread via travelers to industrialized nations of Europe and North America, where the new syndrome was initially recognized as a distinct clinical entity in 1981, even though the number of cases then was minuscule. By 1983, epidemiologists had discerned the routes of transmission and pointed the way for laboratory investigators to identify the etiologic agents. In 1984, the laboratory culturing of HIV was described in the scientific literature, as was the first serologic test for detecting the HIV antibody, which has been used to screen blood donations since 1985. Originally given three different names by the French (1983) and two American (1984) research teams that "discovered" the virus, the name HIV was agreed upon in 1986.
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