Beatrice H. Hahn (born February 13, 1955) is an American virologist and biomedical researcher best known for work which established that HIV, the virus causing AIDS, began as a virus passed from apes to humans. She is a professor of Medicine and Microbiology in the Perelman School of Medicine at the University of Pennsylvania. In November 2002, Discover magazine listed Hahn as one of the 50 most important women scientists. Hahn discovered that the human immunodeficiency virus (HIV) originated in other primates and spilled over to humans. Hahn and her research group established that wild-living chimpanzees in southern Cameroon were a natural reservoir of the closely related simian immunodeficiency viruses (SIVs). The team developed non-invasive techniques for gathering genetic data. By making comparisons between the genes of HIV-1 and SIVs, they found that SIVs had originated in apes, and had passed to humans through multiple connections. The simian versions of the virus (known as SIVcpz in chimpanzees, and SIVgor in gorillas) became the infection named HIV in humans. Hahn later determined that the malaria parasite also traversed from other primates to humans, in a single event. Early life and education Beatrice Hahn was born in Munich, Germany on February 13, 1955. As a child, she was interested in medicine by her father's work as a primary care physician. He was one of the first doctors in Bavaria to use an X-ray machine, and allowed Beatrice to use some of his medical equipment as she grew up. Hahn was fascinated by studying urine slides under the microscope, and taking blood samples. Her ambition to enter medicine dates from this period. Hahn left home to attend medical school at Technical University Munich, where she earned her M.D. degree in 1981. She worked as an intern at Ludwig Maximilian University of Munich from 1981 to 1982. She attained her Doctorate in Medicine from Technical University Munich in 1982. Her doctoral thesis was again influenced by her upbringing and early childhood. It was at this period that she began to specialise in zoonoses or infections which can be transmitted between species, and their implications for public health. Hahn had herded and milked cows as a child in her native Bavaria, where cattle were important to the rural economy. She wondered if human populations might be affected by exposure to bovine viruses. Her thesis specifically focused on the bovine leukemia virus, a very serious disease