Estimating Per-Act HIV Transmission Risk: A Systematic Review, Patel et al., Lippincott Williams & Wilkins (2014)

This study updates previous risk estimates of HIV transmission from parenteral (intravenous), vertical (mother to fetus), and sexual exposures, and assesses the modifying effects of numerous factors including condom use, male circumcision, and antiretroviral therapy. After identifying new studies reporting data on per-act HIV transmission risk and modifying factors, the researchers concluded that the risk of HIV transmission was highest for blood transfusion, followed by vertical exposure, sexual exposures, and other parenteral exposures. Sexual exposure risk was estimated at 138 infections per 10,000 exposures for receptive anal intercourse. Estimated risks of HIV acquisition from sexual exposure were attenuated by 99.2% with the dual use of condoms and antiretroviral treatment of the HIV positive partner. The researchers concluded that the estimates for receptive anal intercourse increased compared with previous estimates, and the risk associated with sexual intercourse was reduced most substantially by the combined use of condoms and antiretroviral treatment of HIV positive partners.