 All patients will be treated with the usual antibiotic treatment for any sexually transmitted infections that are diagnosed during the study. In addition, half will receive acyclovir for 8 weeks , whilst the other half will receive a placebo for 8 weeks. The study medication will reverse in the second 8 weeks of the study. The patients will attend the clinic 3 times per week during the first and the last 8 weeks of the study and once every week during the washout period in the middle of the study - for a total of 18 weeks per participant. At each visit genital and oral samples will be collected. A blood sample will also be collected. For women participants, pregnancy test will be performed. The clinic will provide both pre- and post-HIV test counseling. 