How many sexually-acquired HIV infections in the USA are due to acute-phase HIV transmission?

Objective: To estimate the number of persons in the USA who acquire HIV as a consequence of risky sexual activities with an acutely-infected sex partner. Methods: Estimates of the number of incident infections in the USA that are due to acute-phase HIV transmission were derived from a simple mathematical model that combined epidemiological data with information regarding the relative transmission rates for acutely-infected, nonacutely infected but serostatus-unaware, and serostatus-aware persons living with HIV. Results Approximately 2760 (8.6%) of the estimated 32000 sexually-acquired HIV infections in the USA each year are due to acute-phase transmission of the virus. Multivariate sensitivity analyses with a liberal range of values for key parameters produced an upper bound of 5537 infections, representing 17.3% of the total number of sexually-acquired infections. Conclusions Acute-phase HIV transmission accounts for fewer sexually-acquired infections in the USA than is generally assumed. (c) 2007 Lippincott Williams & Wilkins.