TURUN YLIOPISTON JULKAISUJA ANNALES UNIVERSITATIS TURKUENSIS

SARJA - SER. D OSA - TOM. 1044 MEDICA - ODONTOLOGICA

BURDEN OF INFLUENZA IN CHILDREN by Heli Silvennoinen

TURUN YLIOPISTO UNIVERSITY OF TURKU Turku 2012

From the Department of Pediatrics University of Turku Turku, Finland Supervised by Docent Terho Heikkinen, MD, PhD Department of Pediatrics University of Turku Turku, Finland Reviewed by Docent Janne-Juhana Aittoniemi, MD, PhD Department of Clinical Microbiology FIMLAB Laboratories Tampere, Finland Docent Merja Helminen, MD, PhD Department of Pediatrics Tampere University Hospital Tampere, Finland Opponent Docent Harri Saxén, MD, PhD Hospital for Children and Adolescents University of Helsinki Helsinki, Finland

ISBN 978-951-29-5209-0 (PRINT) ISBN 978-951-29-5210-6 (PDF) ISSN 0355-9483 Painosalama Oy – Turku, Finland 2012





To Marko, Lauri, Anni and Olli

4

Abstract

ABSTRACT Heli Silvennoinen Burden of influenza in children Department of Pediatrics, Institute of Clinical Medicine, University of Turku Annales Universitatis Turkuensis, Medica–Odontologica, Turku, Finland, 2012 Background: Most children with influenza are treated as outpatients but, especially among young children, influenza-attributable illnesses often result in hospitalization. However, relatively scarce data exist on the clinical picture and the full disease burden of pediatric influenza. Prompt diagnosis of influenza could enable the institution of antiviral therapy and adequate cohorting of patients. Data are needed to help clinicians correctly suspect influenza at the time of hospital admission. Aims and methods: We conducted a prospective 2-year cohort study of respiratory infections in children aged ≤13 years to determine the incidence of influenza in outpatient children and to assess the clinical presentation of influenza in various age groups seen in primary care. We also determined the rates of different complications attributable to influenza and the absenteeism of the children and their parents due to the child’s influenza infection. We then conducted a further 16-year retrospective study of children ≤16 years of age, hospitalized with virologically confirmed influenza. We estimated the population-based rates of hospitalizations and determined the primary admission diagnoses of the hospitalized children in different age groups. Results: The average annual rate of influenza was highest (179 / 1000) among children