section_path: History/Origins
section_name: Origins
paragraph_text: Origins
  
  The origin of HIV / AIDS and the circumstances that led to its emergence remain unsolved.
  
  Both HIV-1 and HIV-2 are believed to have originated in non-human primates in West-central Africa and were transferred to humans in the early 20th century. HIV-1 appears to have originated in southern Cameroon through the evolution of SIV(cpz), a simian immunodeficiency virus (SIV) that infects wild chimpanzees (HIV-1 descends from the SIVcpz endemic in the chimpanzee subspecies Pan troglodytes troglodytes). The closest relative of HIV-2 is SIV (smm), a virus of the sooty mangabey (Cercocebus atys atys), an Old World monkey living in coastal West Africa (from southern Senegal to western Ivory Coast). New World monkeys such as the owl monkey are resistant to HIV-1 infection, possibly because of a genomic fusion of two viral resistance genes. HIV-1 is thought to have jumped the species barrier on at least three separate occasions, giving rise to the three groups of the virus, M, N, and O.
  
  There is evidence that humans who participate in bushmeat activities, either as hunters or as bushmeat vendors, commonly acquire SIV. However, SIV is a weak virus which is typically suppressed by the human immune system within weeks of infection. It is thought that several transmissions of the virus from individual to individual in quick succession are necessary to allow it enough time to mutate into HIV. Furthermore, due to its relatively low person-to-person transmission rate, SIV can only spread throughout the population in the presence of one or more high-risk transmission channels, which are thought to have been absent in Africa before the 20th century.
  
  Specific proposed high-risk transmission channels, allowing the virus to adapt to humans and spread throughout society, depend on the proposed timing of the animal-to-human crossing. Genetic studies of the virus suggest that the most recent common ancestor of the HIV-1 M group dates back to c. 1910. Proponents of this dating link the HIV epidemic with the emergence of colonialism and growth of large colonial African cities, leading to social changes, including a higher degree of sexual promiscuity, the spread of prostitution, and the accompanying high frequency of genital ulcer diseases (such as syphilis) in nascent colonial cities. While transmission rates of HIV during vaginal intercourse are low under regular circumstances, they are increased manyfold if one of the partners has a sexually transmitted infection causing genital ulcers. Early 1900s colonial cities were notable for their high prevalence of prostitution and genital ulcers, to the degree that, as of 1928, as many as 45% of female residents of eastern Kinshasa were thought to have been prostitutes, and, as of 1933, around 15% of all residents of the same city had syphilis.
  
  An alternative view holds that unsafe medical practices in Africa after World War II, such as unsterile reuse of single-use syringes during mass vaccination, antibiotic and anti-malaria treatment campaigns, were the initial vector that allowed the virus to adapt to humans and spread.
  
  The earliest well-documented case of HIV in a human dates back to 1959 in the Congo. The virus may have been present in the U.S. as early as the mid-to-late 1950s, as a sixteen-year-old male named Robert Rayford presented with symptoms in 1966 and died in 1969. In the 1970s, there were cases of getting parasites and becoming sick with what was called "gay bowel disease", but what is now suspected to have been AIDS.
  
  The earliest retrospectively described case of AIDS is believed to have been in Norway beginning in 1966, that of Arvid Noe. In July 1960, in the wake of Congo's independence, the United Nations recruited Francophone experts and technicians from all over the world to assist in filling administrative gaps left by Belgium, who did not leave behind an African elite to run the country. By 1962, Haitians made up the second-largest group of well-educated experts (out of the 48 national groups recruited), that totaled around 4,500 in the country. Dr. Jacques Pépin, a Canadian author of The Origins of AIDS, stipulates that Haiti was one of HIV's entry points to the U.S. and that a Haitian may have carried HIV back across the Atlantic in the 1960s. Although there was known to have been at least one case of AIDS in the U.S. from 1966, the vast majority of infections occurring outside sub-Saharan Africa (including the U.S.) can be traced back to a single unknown individual who became infected with HIV in Haiti and brought the infection to the U.S. at some time around 1969. The epidemic rapidly spread among high-risk groups (initially, sexually promiscuous men who have sex with men). By 1978, the prevalence of HIV-1 among gay male residents of New York City and San Francisco was estimated at 5%, suggesting that several thousand individuals in the country had been infected.