Scientists Confirm That HIV Originated in Wild Chimpanzees, Study Says

Scientists on Thursday in a study published in the online edition of the journal Science confirmed that HIV originated in wild chimpanzees and likely crossed over into humans in Cameroon, the New York Times reports (Altman, New York Times, 5/26). Scientists for many years believed that HIV evolved from a similar virus called simian immunodeficiency virus that is found in chimpanzees, but until now that virus had been found only in chimpanzees in captivity (Xinhuanet, 5/26). Beatrice Hahn, a virologist at the University of Alabama-Birmingham, and researchers from the University of Montpellier and the University of Nottingham over seven years collected 599 samples of chimpanzee feces from 10 forest sites in the southern region of Cameroon and tested them for SIV. The scientists were able to trace individual chimpanzees by genetically analyzing the feces. The researchers found evidence of SIV infection in samples that came from five of the 10 forest sites. The researchers recorded an SIV prevalence of about 35% in three chimpanzee communities and a prevalence of 4% and 5% in the two other communities (New York Times, 5/26). All infected chimpanzees had a shared base genetic pattern that suggested a common progenitor of the virus, Hahn said. SIV does not appear to cause illness in chimpanzees, Hahn said (Neergard, AP/WJLA, 5/25).

Implications
Hahn said the new findings do not explain how the virus jumped to humans and spread to become the HIV pandemic. Although scientists believe that HIV appeared in humans as long ago as the 1930s, they do not know how it was transmitted to the first person to contract the virus (Sample, Guardian, 5/26). Hahn and colleagues theorize that the virus likely jumped to humans through exposure to chimpanzee body fluids during the hunting and butchering of bush meat (Hopkin, Nature, 5/25). The authors believe HIV jumped to humans in West-Central Africa because the chimpanzee species that carries SIV is found in Cameroon, Gabon and the Democratic Republic of the Congo (New York Times, 5/26). According to the researchers, if the first human transmission occurred in Cameroon, the virus could have spread as people traveled by river to what is now the D.R.C. capital of Kinshasa -- the site of the first recorded human case of HIV in 1959. Hahn said scientists need to collect more feces samples in other regions of Africa to better understand the evolution of HIV. The study only applies to HIV-1, the most widespread strain of the virus. '"It is quite possible that still other (chimpanzee SIV) lineages exist that could pose risks for human infection and prove problematic for HIV diagnostics and vaccines," the researchers wrote (Fox, Reuters, 5/25). The findings also could help shed more light on how the virus works in humans (Guardian, 5/26).

NPR's "All Things Considered" on Thursday reported on the study. The segment includes comments from Anthony Fauci, director of NIH's National Institute of Allergy and Infectious Diseases, and Hahn (Knox, "All Things Considered," NPR, 5/25). The complete segment is available online in RealPlayer.

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