He is an authority on the mechanisms and consequences of HIV evolution. He created an online database that assists epidemiologists in performing HIV drug surveillance, physicians in interpreting HIV drug resistance tests, and basic scientists in developing new antiretroviral drugs. He is the principal investigator for several NIH-funded HIV drug resistance projects and the technical director of Stanford University Hospital’s Genotypic Antiretroviral Resistance Program. He is one of the pioneers of next-generation deep sequencing technologies for the study of HIV, HBC, and HCV drug resistance.