Risk factors for prolonged H1N1 influenza among hospitalized patients.

In our study, 50% of 42 hospitalized patients with 2009 H1N1 pandemic influenza experienced symptoms longer than 1 week. Older age and delay in oseltamivir initiation were associated with prolonged illness. Patients with pneumonia and fever ≥7 days were more likely to have polymerase chain reaction-positive nasopharyngeal swabs beyond 1 week.