HIV-1 subtype diversity trends in a Northern California cohort.

Between 2000 and 2019, the Stanford Healthcare Clinical Virology Laboratory performed HIV-1 resistance testing for 9199 individuals in Northern California. Nonsubtype B viruses were identified in 3.5%, most often CRF01_AE (1.0%), subtype C (1.0%), CRF02_AG (0.46%), and subtype A (0.45%). Non-B viruses, particularly CRF01_AE and CRF02_AG, increased significantly over time. Although subtype B remained dominant, the rising presence of non-B subtypes reflects growing viral diversity within the U.S. epidemic.