David Da-i Ho was born in Taiwan in 1952. In 1965, when he was 12, he moved to the United States with his mother and brother to join his father, an engineer who was already there, and he grew up in Los Angeles. He earned his medical degree at Harvard in 1978 and trained at Cedars-Sinai Medical Center in Los Angeles, where in 1981, as a resident in internal medicine, he saw some of the first patients with what was later identified as AIDS, and at Massachusetts General Hospital in Boston.

Ho became the founding scientific director of the Aaron Diamond AIDS Research Center in New York. In 1998, his laboratory, with Tuofu Zhu, recovered genetic sequences from the 1959 Blood Sample, confirming it as the oldest known HIV infection. In the mid-1990s, his team carried out a series of studies in patients that measured how quickly HIV reproduces in the body. The work, published in Nature in 1995 with colleagues including the mathematician…