title: Nosocomial vs community-acquired pandemic influenza A (H1N1) 2009: a nested case-control study.
abstract: BACKGROUND
  The characteristics of nosocomial influenza in children are not well described.
  
  
  OBJECTIVE
  To compare the characteristics of nosocomial and community-acquired pandemic influenza A (H1N1) 2009 (pH1N1) in Australian children.
  
  
  METHODS
  In a nested case-control study, the clinical and epidemiological features of nosocomial vs community-acquired pH1N1 were compared among hospitalized children aged <15 years in six paediatric hospitals in Australia between 1 June and 30 September 2009.
  
  
  RESULTS
  Of 506 hospitalized children with pH1N1, 47 (9.3%) were of nosocomial origin. These 47 cases were compared with 141 gender- and age-matched controls. Cases had a significantly higher proportion of underlying medical conditions compared with controls (81% vs 42%, P < 0.001), and were more likely to be exposed to household smokers (36% vs 20%, P = 0.02). Fewer children with nosocomial influenza presented with classical symptoms of influenza, including subjective fever and lethargy. A higher proportion of children with nosocomial influenza received treatment with oseltamivir (77% vs 43%, P < 0.001), and they required a longer stay in hospital following the onset of influenza (mean 8.5 days vs 4.5 days, P = 0.006). Three children (2%) in the community-acquired group died of pH1N1, but there were no deaths in the nosocomial group.
  
  
  CONCLUSIONS
  This study shows that children with pre-existing diseases and those who are exposed to household smokers are more susceptible to nosocomial pH1N1. They may have 'occult presentation' of influenza, but their course of illness is not markedly different from that of children with community-acquired influenza.
authors.affiliation: National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, The Children's Hospital at Westmead and The University of Sydney, Sydney, New South Wales, Australia.
authors.forename: G
authors.initials: G
authors.lastname: Khandaker
authors.forename: H
authors.initials: H
authors.lastname: Rashid
authors.forename: Y
authors.initials: Y
authors.lastname: Zurynski
authors.forename: P C
authors.initials: PC
authors.lastname: Richmond
authors.forename: J
authors.initials: J
authors.lastname: Buttery
authors.forename: H
authors.initials: H
authors.lastname: Marshall
authors.forename: M
authors.initials: M
authors.lastname: Gold
authors.forename: T
authors.initials: T
authors.lastname: Walls
authors.forename: B
authors.initials: B
authors.lastname: Whitehead
authors.forename: E J
authors.initials: EJ
authors.lastname: Elliott
authors.forename: R
authors.initials: R
authors.lastname: Booy
mesh_terms: D000293:Adolescent; D001315:Australia / Q000453:epidemiology; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D017714:Community-Acquired Infections / Q000453:epidemiology* / Q000473:pathology / Q000821:virology; D003428:Cross Infection / Q000453:epidemiology* / Q000473:pathology / Q000821:virology; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000473:pathology / Q000821:virology; D008297:Male; D012307:Risk Factors