While preparing to play in the College All-Star Game against the Green Bay Packers in Chicago in the summer of 1962, Davis awoke with a swollen neck and was hospitalized, with mumps or mononucleosis initially suspected. He was diagnosed with acute monocytic leukemia and began receiving medical treatment. Davis went to Johns Hopkins in Baltimore when he was dying—three months after being diagnosed—and, through chemical treatments, experienced a four- to five-month remission. The disease was incurable, and Davis died at age 23 at Cleveland Lakeside Hospital on May 18, 1963.
