Nationwide Study on the Course of Influenza A (H1N1) Infections in Hospitalized Children in the Netherlands During the Pandemic 2009-2010.

BACKGROUND: The influenza H1N1 pandemic of 2009-2010, provided a unique opportunity to assess the course of disease, as well as the analysis of risk factors for severe disease in hospitalized children (< 18 years). METHODS: Retrospective national chart study on hospitalized children with H1N1 infection during the 2009-2010 pH1N1 outbreak. RESULTS: Nine hundred forty patients (56% boys), median age 3.0 years, were enrolled; the majority were previously healthy. Treatment consisted of supplemental oxygen (24%), mechanical ventilation (5%) and antiviral therapy (63%). Fifteen patients died (1.6%), 5 of whom were previously healthy. Multivariable analyses confirmed pre-existent heart and lung disease as risk factors for intensive care unit admission. Risk factors for mortality included children with a neurologic or oncologic disease and psychomotor retardation. CONCLUSIONS: This nationwide overview of hospitalized children confirms known risk groups for severe influenza infections. However, most of the acute and severe presentations of influenza occurred in previously healthy children.