title: Burden of seasonal influenza hospitalization in children, United States, 2003 to 2008.
abstract: OBJECTIVE
  To estimate the rates of hospitalization with seasonal influenza in children aged <18 years from a large, diverse surveillance area during 2003 to 2008.
  
  
  METHODS
  Through the Emerging Infections Program Network, population-based surveillance for laboratory-confirmed influenza was conducted in 10 states, including 5.3 million children. Hospitalized children were identified retrospectively; clinicians made influenza testing decisions. Data collected from the hospital record included demographics, medical history, and clinical course. Incidence rates were calculated with census data.
  
  
  RESULTS
  The highest hospitalization rates occurred in children aged <6 months (seasonal range, 9-30/10 000 children), and the lowest rates occurred in children aged 5 to 17 years (0.3-0.8/10 000). Overall, 4015 children were hospitalized, 58% of whom were identified with rapid diagnostic tests alone. Forty percent of the children who were hospitalized had underlying medical conditions; asthma (18%), prematurity (15% of children aged <2 years), and developmental delay (7%) were the most common. Severe outcomes included intensive care unit admission (12%), respiratory failure (5%), bacterial coinfection (2%), and death (0.5%).
  
  
  CONCLUSIONS
  Influenza-associated hospitalization rates varied by season and age and likely underestimate true rates because many hospitalized children are not tested for influenza. The proportion of children with severe outcomes was substantial across seasons. Quantifying incidence of influenza hospitalization and severe outcomes is critical to defining disease burden.
authors.affiliation: Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. fdawood@cdc.gov
authors.forename: Fatimah S
authors.initials: FS
authors.lastname: Dawood
authors.forename: Anthony
authors.initials: A
authors.lastname: Fiore
authors.forename: Laurie
authors.initials: L
authors.lastname: Kamimoto
authors.forename: Anna
authors.initials: A
authors.lastname: Bramley
authors.forename: Arthur
authors.initials: A
authors.lastname: Reingold
authors.forename: Ken
authors.initials: K
authors.lastname: Gershman
authors.forename: James
authors.initials: J
authors.lastname: Meek
authors.forename: James
authors.initials: J
authors.lastname: Hadler
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Arnold
authors.forename: Patricia
authors.initials: P
authors.lastname: Ryan
authors.forename: Ruth
authors.initials: R
authors.lastname: Lynfield
authors.forename: Craig
authors.initials: C
authors.lastname: Morin
authors.forename: Mark
authors.initials: M
authors.lastname: Mueller
authors.forename: Joan
authors.initials: J
authors.lastname: Baumbach
authors.forename: Shelley
authors.initials: S
authors.lastname: Zansky
authors.forename: Nancy M
authors.initials: NM
authors.lastname: Bennett
authors.forename: Ann
authors.initials: A
authors.lastname: Thomas
authors.forename: William
authors.initials: W
authors.lastname: Schaffner
authors.forename: David
authors.initials: D
authors.lastname: Kirschke
authors.forename: Lyn
authors.initials: L
authors.lastname: Finelli
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007223:Infant; D007251:Influenza, Human / Q000453:epidemiology* / Q000628:therapy; D008297:Male; D012189:Retrospective Studies; D012621:Seasons; D013997:Time Factors; D014481:United States / Q000453:epidemiology