A vaginal gel with the HIV drug tenofovir, which was created to reduce the odds of HIV transmission, has proved surprisingly effective against genital herpes, The New York Times reports. In a 2010 clinical trial in South Africa, the gel reduced HIV transmission through vaginal intercourse by 39 percent, while reducing genital herpes transmission by 51 percent. A recent study sought to explain the mechanics behind this unexpected result; it found that tenofovir helps disrupt an enzyme herpes needs to duplicate itself. In pill form, tenofovir reduces HIV transmission but has no effect on herpes. Gilead Sciences, which makes tenofovir, is deciding whether to seek approval for marketing the gel as a herpes prevention in the United States. Herpes is more common than HIV. The presence of herpes and other sexually transmitted infections (STIs) can increase the risk of contracting HIV.

To read the Times article, click here.