title: Increase in rates of hospitalization due to laboratory-confirmed influenza among children and adults during the 2009-10 influenza pandemic.
abstract: BACKGROUND
  The Emerging Infections Programs (EIP) network has conducted population-based surveillance for hospitalizations due to laboratory-confirmed influenza among children since 2003, with the network expanding in 2005 to include adults.
  
  
  METHODS
  From 15 April 2009 through 30 April 2010, the EIP conducted surveillance among 22.1 million people residing in 10 states. Incidence rates per 100 000 population were calculated using US Census Bureau data. Mean historic rates were calculated on the basis of previously published and unpublished EIP data.
  
  
  RESULTS
  During the 2009 pandemic of influenza A virus subtype H1N1 infection, rates of hospitalizations due to laboratory-confirmed influenza were 202, 88, 49, 31, 27, 36, 28, and 27 episodes per 100 000 among persons aged <6 months, 6-23 months, 2-4 years, 5-17 years, 18-49 years, 50-64 years, 65-74 years, and ≥75 years, respectively. Comparative mean rates from previous influenza seasons during which EIP conducted surveillance were 153, 53, 20, 6, 4, 8, 20, and 56 episodes per 100 000 among persons aged <6 months, 6-23 months, 2-4 years, 5-17 years, 18-49 years, 50-64 years, 65-74 years, and ≥75 years, respectively.
  
  
  CONCLUSIONS
  During the pandemic, rates of hospitalization due to laboratory-confirmed influenza among individuals aged 5-17 years and 18-49 years increased 5-fold and 6-fold, respectively, compared with mean rates from previous influenza seasons. Hospitalization rates for other pediatric and adult age groups increased, compared with mean rates from previous influenza seasons, whereas the rate among individuals aged ≥75 years decreased.
authors.affiliation: Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA.
authors.forename: Chad M
authors.initials: CM
authors.lastname: Cox
authors.forename: Tiffany
authors.initials: T
authors.lastname: D'Mello
authors.forename: Alejandro
authors.initials: A
authors.lastname: Perez
authors.forename: Arthur
authors.initials: A
authors.lastname: Reingold
authors.forename: Ken
authors.initials: K
authors.lastname: Gershman
authors.forename: Kimberly
authors.initials: K
authors.lastname: Yousey-Hindes
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Arnold
authors.forename: Monica M
authors.initials: MM
authors.lastname: Farley
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: Joan
authors.initials: J
authors.lastname: Baumbach
authors.forename: Emily B
authors.initials: EB
authors.lastname: Hancock
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: Lyn
authors.initials: L
authors.lastname: Finelli
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification* / Q000472:pathogenicity*; D007251:Influenza, Human / Q000453:epidemiology* / Q000473:pathology* / Q000821:virology; D008297:Male; D008875:Middle Aged; D058873:Pandemics; D014481:United States / Q000453:epidemiology; D055815:Young Adult