Origin of HIV

Origin of HIV

Where did HIV originate? First, HIV-2 is very closely related to SIV, the simian immune virus, found in sooty mangabeys. Baboons can be infected with HIV-1 and they can also suffer from a version of SIV. At the 6^th American Conference on Retroviruses and Opportunistic Infections held in Chicago from January 31-February 4, 1999, one of the keynote papers delivered by Beatrice Hahn on the first day presented evidence that HIV-1 is likely to have originated in West African chimpanzees of the species Pan troglodytes troglodytes. HIV could have been transferred from monkeys because they have long been kept as pets and used for food. When hunting monkeys it is not unusual for both the hunter and the hunted to exchange blood during capture. Currently there is a large market in "bush meat" obtained from monkeys. This does not bode well because there may well be continuing transfer of the disease from monkeys to humans.

The earliest fully documented case of HIV dates back to 1959. A Congolese man's blood sample from a medical study was preserved, found, and then analyzed in 1998. It was verified that he had been HIV+. Other suspected, but unverified because of the lack of either blood or tissue samples, cases date back as early as 1934. On February 1, 2000, M. Korber, et al. reported the results of a phylogenetic statistical analysis of the evolution of the retroviral genome of HIV using complex mathematical models allowing for both constant and variable rates of evolution. Her group's analysis required the use of supercomputers to backtrack the evolution to its source from monkeys. The most reliable time of origin in humans is somewhere around 1930 (a 95% confidence interval extends from 1910 to 1950). Several naysayers have claimed that the disease originated from the use of African green monkey kidneys to cultivate poliovirus in the late 1950's and early 1960's. This analysis finds that argument to be a very low probability event, hence quite unlikely.

The first recorded cases in the U.S. occurred in New York City in 1952, 1959, and 1979. The cases from the 1950s were both males with PCP and other unusual infections. The first reported cases were those in the June 5, 1981 MMWR mentioned earlier. The watershed event that brought the disease into full view of the public eye was the announcement that the (thought to be very macho) film star Rock Hudson had the disease. (Even after he had been diagnosed with AIDS, he continued cruising the gay bars and did not notify any of his sexual partners of his HIV status.)