"We believe we have discovered a subspecies of chimpanzees that has been the source of the human AIDS virus, HIV-1," Hahn says.
While chimps have long been suspected as the source, "there have been a lot of loose ends that made people uncomfortable drawing that conclusion," Hahn says.
The chimp version of the AIDS virus -- the microbe now thought to be the grandfather of HIV -- is called SIVcpz. Hahn isolated the SIVcpz strain from the chimpanzee species Pan troglodytes troglodytes, which inhabits the area of central Africa where AIDS first appeared.
"So here is a species very closely related to us, basically infecting with a very similar virus," Hahn says.
Hahn also believes she knows how the virus jumped from chimps to humans. The chimps are often trapped and butchered by west Africans for bush meat, but the slaughtering techniques are primitive, and chimp blood often comes in contact with hands that are full of nicks and cuts.
"We believe, not knowing for sure, that either the transmission occurs when hunters get in contact with infected blood or through bites," Hahn says.
The chimps are believed to have carried the virus for 100,000 years, and may provide researchers with an interesting tool. Because they get infected, but don't get sick, they could open new doors to the treatment of HIV infection in humans.
"It may steer us towards being able to learn more, for example, about vaccine development or about enhancing that particular component of the immune system which protects the chimp. (That) would hopefully, correspondingly, protect mankind," explains Dr. Anthony Fauci of the National Institutes of Health.
What may stand in the way of those potential discovering is the fact that the chimp has been hunted to the brink of extinction.