Effect of Tenofovir on Genital Herpes Simplex Virus (HSV) Shedding

The investigators propose a randomized, double-blind, placebo-controlled, cross-over study of 55 adult, healthy women who are HSV-2 seropositive and HIV-1 seronegative. Women will first participate in a run-in phase with twice daily swabbing. Following 4 weeks of swabbing, participants will be randomized 2:2:1 to one of three groups: 1) oral tenofovir and placebo gel, 2) oral placebo and tenofovir gel, or 3) oral placebo and placebo gel. Participants will begin treatment and swab the genital region twice daily for 5 more weeks. Study drug will be administered daily.