Wilbur George Downs, 77, a tropical medicine expert and epidemiology professor at the Yale School of Medicine. As a lieutenant colonel in World War II, Downs served as chief of preventive medicine for the Island Command in Okinawa. After the war, he was assigned by the Rockefeller Foundation to direct a malaria control program in Mexico. In 1952, the foundation asked him to establish a program in Trinidad to investigate mosquito- and tick-borne viruses. He founded the Trinidad Regional Virus Laboratory, now the Caribbean Epidemiology Center, in Port-of-Spain. Downs negotiated the move of the Rockefeller Foundation Virus Laboratory to Yale in 1963 and became an associate director of the foundation, director of the Yale Arbovirus Research Unit and a professor of epidemiology. In Branford, Conn., on Feb. 17 of a heart attack.