For HIV infected persons, the results mean that antiviral treatment not only improves health and survival but goes a long way in preventing sexual transmission of the virus to uninfected partners. But there also is an important "take-home" message for sexually active persons without HIV: if a person's sex partner has HIV and is taking anti-HIV therapy, the chance of sexual transmission is much lower than it otherwise would be. This is especially so if the infected person has a low viral load, meaning they have small amounts of HIV in their blood, or none at all. Of course it remains wise to discuss mutual HIV status prior to sex with a new partner and avoid vaginal or anal sex with partners known to have HIV, and to use condoms routinely for vaginal or anal sex outside mutually monogamous relationships. But these very important research results should help reassure persons who, after an exposure, learn their partners have HIV but are on treatment for it.
In the future, we can anticipate additional helpful research outcomes from HPTN 052. Since the inception of MedHelp's HIV Prevention forum and Sexually Transmitted Disease forum, and more recently the HIV - International forum, one of the most common questions we field regards the probability of catching HIV after a sexual exposure. The available data are imprecise. We often quote figures like 1 chance in 1,000 to 2,000 for transmission by a single, unprotected vaginal sex exposure, if one partner is infected. Such data, which have been published by the U.S. Centers for Disease Control and Prevention (CDC), are rough estimates at best, because they are based primarily on people's recollections of sexual exposures in the months and years before they tested positive. In HPTN 052, the research subjects were asked to keep careful records of their sexual exposures. Analysis of these data should give more precise estimates of transmission risk for vaginal intercourse. Whether there was sufficient frequency of oral or anal sex for accurate calculation remains to be seen — but perhaps we will have improved information for those practices as well.
We congratulate our colleague and close friend, Myron (Mike) Cohen, MD, of the University of North Carolina, principal investigator on HTPN 052. This work is a crowning achievement in Dr. Cohen's already outstanding career in research on STDs and HIV/AIDS.
Edward W. Hook, III, MD, is a professor of medicine and epidemiology at the University of Alabama at Birmingham and recognized expert in STDs and HIV/AIDS prevention and treatment. In 2009, Dr. Hook received the American STD Association's Thomas Parran Award, the nation's highest honor in the field of STD research and prevention.
H. Hunter Handsfield, MD, is a clinical professor of medicine at the University of Washington and a senior research leader at the Battelle Centers for Public Health Research, where he focuses on domestic and international HIV prevention research especially HIV/STD prevention in Zimbabwe. Dr. Handsfield was the 2010 recipient of the Thomas Parran Award.
Published May 17, 2011
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