Reflecting on how integral a role cattle played in rural Bavaria, Hahn wondered if the close relationship of people and cattle could be detrimental to the humans, through exposure to bovine virus. Her thesis specifically focused on the bovine leukemia virus, a very serious disease in cattle, which is closely related to the human tumor virus HTLV-1.[2] Hahn would later continue her research and interest in the public health ramifications of animal-human contact in her research on zoonoses.[2]