HIV transmission in the United States: considerations of viral load, risk behavior, and health disparities.

Ongoing HIV transmission is related to prevalence, risk behavior and viral load among persons with HIV. We assessed the contribution of these factors to HIV transmission with transmission rate models and data reported to National HIV Surveillance and published rates of risk behavior. We also estimated numbers of persons with risk behaviors and unsuppressed viral load among sexual risk groups. The transmission rate is higher considering risk behavior (18.5 infections per 100 people with HIV) than that attributed to unsuppressed viral load (4.6). Since persons without risk behavior or suppressed viral load presumably transmit HIV at very low rates, transmission can be attributed to a combination of these factors (28.9). Service needs are greatest for MSM; their number with unsuppressed viral load engaging in unprotected discordant sex was 8 times the number of male heterosexuals and more than twice the number of female heterosexuals with high-risk transmission potential. While all persons with HIV need optimal care, treatment as prevention is most relevant when risk behavior is present among persons with unsuppressed HIV viral load.