Dr. Koss conducts clinical research on HIV prevention and treatment, with a major focus on developing strategies to optimize uptake of and adherence to pre-exposure prophylaxis (PrEP) among women in the United States and East Africa. She also has an interest in adherence to treatment and virologic outcomes among pregnant and postpartum women living with HIV. She is an attending physician on the HIV and Infectious Diseases consult service at San Francisco General and a clinical provider at the "Ward 86" Positive Health Practice, where she serves as physician lead for one of three provider panels.