This retrospective population based study calculated the rate of excess hospital admissions due to influenza in children aged 15 or under with acute respiratory disease. The data were collected from the Hospital Authority of the Hong Kong Special Administrative Region, China. The excess admissions were calculated using an excess hospital admission model from periods of influenza peaks and baseline respiratory syncytial virus rates (7 weeks each in 1998 and 1999). The adjusted rates of influenza-related excess hospital admissions for 1998 and 1999 per 10 000 children were 278.5 and 288.2 for children aged <1 year, 218.4 and 209.3 for those aged 1–<2 years, 125.6 and 77.3 for those aged 2–<5 years, 57.3 and 20.9 for children aged 5–<10 years, and 16.4 and 8.1 for children aged 10–15 years. Influenza-related excess admissions accounted for 38 606 extra bed-days (5.5–8.2% of all paediatric bed-days). These influenza-related hospital admission rates for children are much higher than previously published figures. Possible explanations suggested are the inclusion of high risk patients, differences in admission practice, and higher influenza attack rates in crowded communities.

The reasons for higher influenza-related hospital admission rates in this subtropical climate compared with temperate regions need further investigation. The study highlights the rationale for continued worldwide influenza surveillance, the major impact of this common infection, and the need for effective prevention.