 This randomized, double-blind, multi-center study of Tamiflu Oseltamivir will evaluate the efficacy against viral activity, the effectiveness in resolving the disease symptoms, and the safety and tolerability in patients with influenza. Patients with H1N1 2009 influenza strain or influenza A are eligible for this study. Patients will be randomized to one of four treatment regimens. Patients will receive oral doses of either 75 mg adults or 150 mg adults of study drug twice daily for 5 or 10 consecutive days. The dose will be body weight-adjusted for pediatric patients. 