Transmission Fitness of Drug‐Resistant Human Immunodeficiency Virus and the Prevalence of Resistance in the Antiretroviral‐Treated Population

Although the prevalence of drug-resistant strains in primary human immunodeficiency virus (HIV) infection in North America has recently increased, their transmission fitness remains unknown. The present study estimated the frequency of transmission of drug-resistant HIV from patients receiving antiretroviral therapy using retrospective surveys of clinic data. It revealed that resistant virus was transmitted only approximately 20% as frequently as expected from these patients. Individuals with primary resistance may become a significant source of resistant strains.