Hahn discovered that the human immunodeficiency virus (HIV) originated in other primates and traversed to humans.[1] Hahn and her research group established that wild-living chimpanzees in southern Cameroon were a natural reservoir of Simian immunodeficiency viruses (SIVs). They developed non-invasive techniques for gathering genetic data. By making genetic comparisons between HIV-1 and SIVs, they found that SIVs had traversed between humans and nonhuman primate species through multiple connections.[3][1] HIV resulted from cross-species infections, with SIVs traveling from chimpanzees (SIVcpz) and gorillas (SIVgor) to humans.[4] Hahn later determined that the malaria parasite also traversed from other primates to humans, in a single event.[4]