A 33-year-old woman with HIV and a recent CD4 count of 422 cells/mm³ is seen in clinic complaining of a 1-day history of painful genital lesions. She recalls several similar episodes in the past. On examination, she has several shallow-based vaginal ulcers with erythematous borders. You collect a sample from the base of a ruptured vesicle to send for herpes simplex virus (HSV) PCR. While awaiting the results, you opt to start empiric treatment for genital HSV infection.