All patients receive acyclovir IV every 8 hours on days 1-21. On day 19, patients undergo a lumbar puncture and must have a negative CSF PCR to be randomized. If patients have a positive CSF PCR on day 19, they continue to receive acyclovir IV every 8 hours. Treatment continues every 7 days with a repeat CSF PCR on the fifth day until a negative CSF PCR result is achieved. Patients are then randomized to one of two treatment arms.