HIV-1, the virus behind the global AIDS pandemic, began as a simian immunodeficiency virus, SIVcpz, carried by central chimpanzees (Pan troglodytes troglodytes) in the forests of southern Cameroon. The explanation most researchers accept is that a person who hunted or butchered a chimpanzee for bushmeat was exposed to the animal's infected blood, and the virus adapted to its new human host.

The proof that wild chimpanzees were the reservoir came on May 25, 2006, when a team led by Beatrice Hahn, then at the University of Alabama at Birmingham, published Chimpanzee Reservoirs of Pandemic and Nonpandemic HIV-1 online in Science. Instead of handling endangered apes, the researchers collected 599 fecal samples at ten forest sites across southern Cameroon and tested them for the virus. In some chimpanzee communities, 29 to 35 percent of the animals were infected. The strains found in the southeastern corner of the country were the closest known relatives of HIV-1 group M, the lineage responsible for nearly all infections worldwide,…