False-color scanning electron micrograph of<unk> -1, in green, budding from cultured lymphocyte<unk>  is caused by a human immunodeficiency virus <unk> , which originated in non-human primates in Central and West Africa. While various sub-groups of the virus acquired human infectivity at different times, the global pandemic had its origins in the emergence of one specific strain –<unk> -1 subgroup M – in Léopoldville in the Belgian Congo (now Kinshasa in the Democratic Republic of the Congo) in the 1920s. There are two types of<unk> :<unk> -1 and<unk> -2.<unk> -1 is more virulent, easily transmitted and is the cause of the vast majority of<unk>  infections globally. The pandemic strain of<unk> -1 is closely related to a virus found in chimpanzees of the subspecies Pan troglodytes troglodytes, which live in the forests of the Central African nations of Cameroon, Equatorial Guinea, Gabon, the Republic of the Congo, and the Central African Republic.<unk> -2 is less transmittable and is largely confined to West Africa, along with its closest relative, a virus of the sooty mangabey (Cercocebus atys atys), an Old World monkey inhabiting southern Senegal, Guinea-Bissau, Guinea, Sierra Leone, Liberia, and western Ivory Coast.
History of HIV/AIDS
History of chemical warfare
History of smallpox
History of polio
History of leprosy
History of tuberculosis
History of syphilis
History of plague