A Study on Higher-dose Oseltamivir Treatment's Impact on Viral Clearance and Clinical Recovery in Adults Hospitalized With Influenza

• The investigators plan to study the impact of higher-dose oseltamivir (150 mg b.d.) treatment on rate of viral load decline and RNA negativity (in nasal and throat swabs, assessed by quantitative RT-PCR assay) and time to clinical recovery in adult patients hospitalized for severe influenza.
• Patients who received intervention (oseltamivir 150 mg b.d. for 5 days) will be compared to those in the non-intervention arm (patients may receive oseltamivir treatment at 75 mg b.d. for 5 days, decided by their managing physicians) in the two respective study sites. Viral load changes and viral clearance will be compared. Clinical progress and time to symptom recovery will be reported. The protocol will be crossed-over to the other site at a defined time frame.
• oseltamivir 150 mg b.d. has been shown to be safe and well-tolerated in earlier clinical trials
• higher-dose treatment has been suggested by health authorities (e.g. WHO) to treat severe influenza infection/pneumonia.

Inclusion criteria

• confirmed influenza A (H1N1, H3N2) or B infection by IFA or RT-PCR, with a compatible clinical illness
• presented within 96 hours from symptom onset
• age >/= 18 years

Exclusion criteria

• lack of consent
• suspected avian influenza
• patients who have received antivirals against influenza prior to admission
• suspected or confirmed oseltamivir resistance
• pre-existing renal impairment, with creatinine clearance <40 ml/min
• pre-existing hepatic failure
• participation in a clinical study involving experimental medication in the past 4 weeks
• pregnant women, or who are attempting to become pregnant, or who are breast feeding.