In 1978, Keusch was appointed professor of medicine at the Tufts-New England Medical Center. He also held the title of Chief Division of Geographic Medicine and Infectious Diseases. There he established a major research and training program in infectious diseases and international health. Keusch served concurrently as Scientific Director of the Health Group at the Harvard Institute for International Development where he oversaw long-term projects to increase research capacity in developing countries. His research included HIV studies where he directed one of the NIH-supported International Collaboration on AIDS Research projects. By the 1990s, he had consequently become an internationally recognized authority on infectious disease.
