Researchers at the XVII International AIDS Conference in Mexico City affirmed that long-term treatment of genital herpes with the drug acyclovir does not reduce HIV transmission risk, Reuters reports.

In a randomized trial, researchers evaluated the effects of acyclovir in 1,814 men who have sex with men (MSM) from the United States and Peru, and in 1,358 women from Zimbabwe, Zambia and South Africa. All were HIV negative and living with herpes simplex virus type 2 (HSV-2), which causes genital herpes.

Participants took acyclovir or placebo pills twice each day and were followed monthly for up to 18 months. After that period, researchers observed that incidences of HIV infection were the same in both groups.

According to the article, researchers suggest that genital herpes may be a risk marker—not a risk factor—for HIV, and they suggested that interventions against HSV-2 should be better implemented in these regions.