Estimating the undetected burden of influenza hospitalizations in children

During the 2004–2005 influenza season two independent influenza surveillance systems operated simultaneously in three United States counties. The New Vaccine Surveillance Network (NVSN) prospectively enrolled children hospitalized for respiratory symptoms/fever and tested them using culture and RT–PCR. The Emerging Infections Program (EIP) and a similar clinical-laboratory surveillance system identified hospitalized children who had positive influenza tests obtained as part of their usual medical care. Using data from these systems, we applied capture–recapture analyses to estimate the burden of influenza related-hospitalizations in children aged