title: Age-matched comparison of children hospitalized for 2009 pandemic H1N1 influenza with those hospitalized for seasonal H1N1 and H3N2.
abstract: BACKGROUND
  A wide spectrum of clinical manifestation ranging from deaths to a mild course of disease has been reported in children infected with the 2009 pandemic H1N1 (pH1N1) influenza.
  We conducted an age-matched control study comparing children hospitalized for pH1N1 with historic controls infected with seasonal H1N1 and H3N2 influenza to correct for the effect of age on disease susceptibility and clinical manifestations. We also compared children with pH1N1 to children concurrently admitted for seasonal influenza during the pandemic period to adjust for differences in health-seeking behavior during the pandemic or other potential bias associated with historic controls. There was no death or intensive care admission. Children with pH1N1 were more likely to have at least one risk condition for influenza, an underlying chronic pulmonary condition, more likely to have asthma exacerbation and to be treated with oseltamivir. There was no difference in other aspects of the clinical course or outcome.
  
  
  CONCLUSIONS
  Disease manifestation of children hospitalized for pH1N1 infection was mild in our patient population.
authors.affiliation: Department of Paediatrics and Adolescent Medicine, The University of Hong Kong, Pokfulam, Hong Kong. ssschiu@hkucc.hku.hk
authors.forename: Susan S
authors.initials: SS
authors.lastname: Chiu
authors.forename: Kwok-Hung
authors.initials: KH
authors.lastname: Chan
authors.forename: Wilfred H S
authors.initials: WH
authors.lastname: Wong
authors.forename: Eunice L Y
authors.initials: EL
authors.lastname: Chan
authors.forename: J S M
authors.initials: JS
authors.lastname: Peiris
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D015982:Bias; D002648:Child; D002675:Child, Preschool; D019411:Clinical Laboratory Techniques; D005260:Female; D015438:Health Behavior; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000472:pathogenicity*; D053122:Influenza A Virus, H3N2 Subtype / Q000472:pathogenicity*; D007251:Influenza, Human / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D008297:Male; D058873:Pandemics / Q000706:statistics & numerical data*; D012306:Risk; D012621:Seasons