A multi-center study using the Internet was performed during the influenza season of 2002-2003 to evaluate the effectiveness of recently developed anti-influenza drugs. The study included 2980 cases of influenza diagnosed by rapid detection test at 52 clinics in Japan. In the oseltamivir and zanamivir groups, the duration of fever ( greater than or equal to 37.5 degreesC) was longer in patients with the type B influenza virus than with type A. In patients with type A, who began drug treatment within 24 h of onset, the duration of fever was significantly shorter in the amantadine (2.47 days), oseltamivir (2.49 days), and zanamivir (2.36 days) groups than in 22 patients receiving no anti-influenza drugs (3.52 days). The duration of fever was significantly longer in children than in adults, and shorter in patients receiving early therapy than in patients with delayed therapy. Of 487 patients administered oseltamivir within 12 h of onset, 16.4% became afebrile at 24 h and 49.3% at 36 h after onset. The effectiveness of oseltamivir was affected by the patient's age and the type of influenza. In addition, oseltamivir was more effective when administered as early as possible after the onset of the symptoms of influenza. (C) 2003 Elsevier B.V. All rights reserved.
