Arm I: Patients receive oral acyclovir three times a day for 6 months. Arm II: Patients receive placebo. In case of cutaneous recurrence during the first 12 months of the study, patients receive open label oral acyclovir (if CSF PCR is negative) or acyclovir IV (if CSF PCR is positive) for 5 days. Patients may or may not continue on study drug following this treatment.