The impact of winter epidemics of influenza and respiratory syncytial virus on paediatric admissions to an urban general hospital.

To demonstrate the impact of influenza epidemics on pediatric hospital admissions, admissions that were attributable to influenza and respiratory syncytial virus (RSV) infection to the pediatric ward of an urban general hospital in Japan were followed-up during a 4-month period from December to March 1991 through 1998. During the 1997-1998 influenza type A (H3N2) epidemic, a diagnosis of influenza type A (H3N2) was made in 26.3% of all patients admitted aged 15 years or lower. During the peak of the epidemic, as many as 50-70% of the admissions were attributable to influenza type A (H3N2). In the seven winters from 1991 to 1988, 14.0% of all admissions were associated with infection with influenza virus (mean age 4.4 years), and 17.5% were due to RSV. More patients were admitted to hospital for influenza than RSV infection in three of the seven seasons. Among the patients with influenza, 74.5% of the cases were previously healthy children. Influenza and RSV infection are leading causes of pediatric hospital admissions during the winter. Effective methods of prophylaxis are needed not only for high-risk patients, but for healthy young children.