Research published in the 9 November 2006 issue of Nature has, for the first time, identified an HIV-1-like virus in primates other than chimpanzees and humans. Lead author Martine Peeters of the University of Montpellier in France says that this is the “first time someone has looked at HIV infection in wild living gorillas” (National Geographic News, 9 November 2006). By testing fecal samples from gorillas living in remote forest regions of Cameroon, her group showed that HIV-1-like simian immunodeficiency virus (SIV) infection is endemic in these gorillas.

Of the three strains of HIV-1 that infect humans — strains M, N and O — two (M and N) have previously been shown to have crossed the species barrier from chimpanzees. Strain M has resulted in the global AIDS pandemic, whereas strain N has infected only a few individuals in Cameroon. The identification of a lineage of SIV in wild gorillas (SIVgor) that is more closely related to the O strain of HIV-1 than is any other known type of SIV now indicates the probable primate source of this human infection.

It is still unclear, however, how this strain was acquired by gorillas or transmitted to humans. Chimpanzees could have transmitted HIV-1 strain-O-like viruses to gorillas and humans independently or first to gorillas that then transmitted the virus to humans. Peeters thinks that the primary reservoir is probably still in chimpanzees, “but we don't know who transmitted it to humans — the gorilla or the chimp” (Reuters Health, 8 November 2006). Given that gorillas are vegetarian and rarely encounter chimpanzees in the wild, further studies will be necessary to clarify the route of transmission (Nature). People who hunt gorillas for food or for use in traditional medicines might be at risk of contracting HIV, according to Peeters (Washington Post, 9 November 2006).