Recent data suggest that as many as 85% of people living with HIV also carry genital herpes (HSV). “Having HSV, particularly during an outbreak, increases amounts of HIV in genital secretions and increases chances of transmitting HIV,” says Antonio Urbina, MD, medical director of HIV/AIDS education and training at St. Vincent’s Hospital in New York City. Indeed, the Centers for Disease Control and Prevention estimates that herpes sores make an HIV negative person three to five times more likely to acquire HIV during sex with a positive partner. Another complication: Though condoms have long been shown to be highly effective in blocking HIV transmission, their strength against herpes has proved inconclusive.

That is, until now. A study published in the Annals of Internal Medicine last November followed 1,843 men and women at risk for herpes for 18 months. Consistent condom use reduces risk of herpes by 50%, says study author Anna Wald, MD, director of the Virology Research Clinic at the University of Washington. But she warns, “Condoms don’t protect against herpes as well as they do against other STDs—such as HIV—because herpes can be active on a larger area of the genital skin, including that which is not covered by condoms.” Dr. Wald also recommends further reducing risk by getting tested regularly for HSV antibodies. If you already know that you are infected, taking antiviral medications for HSV has been shown to greatly reduce transmission. Spread the word—and the latex.