A preventative HIV medication may help protect those who take it against contracting the herpes virus as well. This extra protection was discovered during a randomized trial in which participants took drugs to prevent HIV infection as the central focus for the trial.

Participants in the trial took daily doses of medication that included tenofovir, which has been shown to lower the risk of HIV contraction by 75 percent. Further analysis revealed the reduced risk of herpes contraction.

This extra protection is thought to be especially beneficial for couples where one of the partners has HIV and the other does not. The presence of herpes is known to increase the risk of HIV contraction. According to research, this increase can be anywhere from three- to six-fold.

The study that found this connection used 4,747 heterosexual partners from Africa and followed the partners from July of 2008 to November 2010. Testing for the effects of tenofovir did not take place until analysis of a pericoital gel containing one percent of the drug was determined to be effective in preventing transmission of the herpes virus. Following this discovery, subgroup analyses were performed that supported the efficacy of tenofovir against the herpes virus. They tested this by analyzing samples taken from the last study follow up against couples who were free of the herpes virus at the start of the trial.

The analysis revealed that 33 percent of those exposed to the herpes virus while taking tenofovir did not contract the virus.

Participants were noted to have adhered to their treatments well. Researchers reported that 98 percent of the medication bottles were returned with a collective 96 percent of the medication having been taken. The high rate of adherence, coupled with the high rate of avoided infections indicates that tenofovir may be the most effective protection available for couples where at least one is at high risk for exposure.