Acyclovir efficiently inhibits oropharyngeal excretion of Epstein-Barr virus in patients with acute infectious mononucleosis.

Shedding of Epstein-Barr virus (EBV) into saliva was studied in 31 patients with verified acute infectious mononucleosis. The patients had been randomized for intravenous treatment with acyclovir (ACV) at 10 mg/kg body weight at 8 h intervals for 7 days, or placebo, in a double-blind trial. EBV in centrifuged throat washings was detected by transformation of umbilical cord lymphocytes and by immunofluorescence staining for EBV-associated nuclear antigen in fixed cell smears. Saliva samples were obtained before and during treatment, and after 4 weeks and 6 months, respectively. ACV effectively but transiently interrupted EBV production (P less than 0.001), but virus shedding resumed at the initial level within 3 weeks of cessation of the treatment. Initially, 93.5% of the patients had detectable EBV in the saliva compared with 83% in the 4th week and 58% after 6 months.