75 mg oseltamivir orally twice daily for 5 days within 72 hours of symptom onset

75mg placebo calcium carbonate pills taken twice daily for five days within 72 hours of symptom onset and will be identical in appearance to oseltamivir

They will be assessed for eligibility at the clinics and those randomized to the intervention will receive oseltamivir 75 mg orally twice daily for 5 days within 72 hours of symptom onset. Participants randomized to the control group will receive calcium carbonate placebo pills twice daily for five days within 72 hours of symptom onset. For patients with a known creatinine clearance < 10 ml/min, the recommended dose of 75mg orally daily for 5 days of either intervention or placebo will be administered.

A non-elective admission to hospital, in contrast to visits to the emergency department where admission does not take place. However, a prolonged stay in the emergency department (> 24 hours) will also be considered to be hospitalization. Events that occur beyond this time period are deemed unlikely to be directly related to influenza,except functional status which will be assessed up to three months following acute respiratory infection. Secondly, the hospitalization must also be considered to be due to acute respiratory illness. An adjudication committee (comprised of two infectious diseases physicians who also practice general internal medicine) blinded to study group allocation will review data for hospitalization. They will be asked to judge whether the hospitalization was definitely or probably related to the acute respiratory illness. Those judged to be definitely or probably related will be considered as our primary outcome.

lower respiratory tract infection including exacerbation of chronic pulmonary disease