The study included 3351 patients in whom influenza had been diagnosed by use of an antigen detection test kit.Oseltamivir was administered to 1818 patients with influenza A and 1485 patients with influenza B. No anti-influenza drugs were administered to 21 patients with influenza A or to 27 patients with influenza B. Patients receiving oseltamivir therapy were divided into 4 groups according to the time between the onset of fever (temperature, > or = 37.5 degrees C) and administration of the first dose of oseltamivir (0-12 h, 13-24 h, 25-36 h, and 37-48 h)