Pediatric hospitalizations with influenza A infection during the 2009-2010 pandemic in five hospitals in Japan

Background: The aim of this study was to identify the clinical characteristics of hospitalized children with the 2009 pandemic influenza virus infection in Japan. Methods: We retrospectively reviewed cases of hospitalized children younger than 16 years with laboratory-confirmed influenza A virus infection during the 20092010 pandemic season in five hospitals in Japan. Results: A total of 515 cases were included in the analysis. The median age was 6.3 years (range 015), and 216 subjects (41.9%) had one or more underlying medical conditions. There were no fatalities, but 16 patients (3.1%) required intensive care. More than 93% of the subjects received neuraminidase inhibitors, and more than 87% received these medications within 48 h of the onset of symptoms. Approximately 80% of all subjects were admitted to hospital within 48 h of the onset of symptoms. Conclusions: There were no fatalities, and the proportion of patients with serious illness was substantially lower than previously reported from other countries. Good access to medical services and proactive treatment may have contributed to the lower disease burden of the 2009 influenza pandemic on Japanese children.