Herpes simplex virus type 2 (HSV2), the most common cause of genital herpes, increases a woman's risk of HIV acquisition from 3-6 fold, perhaps because HSV2-infected women have increased numbers of HIV "target cells" (CD4 T cells and dendritic cells) in the cervical mucosa. However, recent clinical trials showed no impact of HSV2 suppression on HIV acquisition rates. The reasons for this negative result are unclear. The investigators propose to examine the effect of valacyclovir (a widely used herpes medication) treatment on cervical immunology and HIV target cells in the cervix. The study will take the form of a randomized, double-blind, placebo-controlled crossover trial. Primary endpoints will be (1) the number of CD4 T cells on a cervical cytobrush and (2) the number of immature dendritic cells per cervical cytobrush.