title: Clinical epidemiology and predictors of outcome in children hospitalised with influenza A(H1N1)pdm09 in 2009: a prospective national study.
abstract: BACKGROUND
  There are few large-scale, prospective studies of influenza A(H1N1)pdm09 in children that identify predictors of adverse outcomes.
  
  
  OBJECTIVE
  We aimed to examine clinical epidemiology and predictors for adverse outcomes in children hospitalised with influenza A(H1N1)pdm09 in Australia.
  
  
  METHODS
  Active hospital surveillance in six tertiary paediatric referral centres (June-September, 2009). All children aged <15 years admitted with laboratory-confirmed influenza A(H1N1)pdm09 were studied.
  
  
  RESULTS
  Of 601 children admitted with laboratory-confirmed influenza, 506 (84·2%) had influenza A(H1N1)pdm09. Half (51·0%) of children with influenza A(H1N1)pdm09 were previously healthy. Hospital stay was longer in children with pre-existing condition (mean 6·9 versus 4·9 days; P = 0·02) as was paediatric intensive care unit (PICU) stay (7·0 versus 2·3 days; P = 0·005). Rapid diagnosis decreased both antibiotic use and length of hospital and PICU stay. Fifty (9·9%) children were admitted to a PICU, 30 (5·9%) required mechanical ventilation and 5 (0·9%) died. Laboratory-proven bacterial co-infection and chronic lung disease were significant independent predictors of PICU admission (OR 6·89, 95% CI 3·15-15·06 and OR 3·58, 95% CI 1·41-9·07, respectively) and requirement for ventilation (OR 5·61, 95% CI 2·2-14·28 and OR 5·18, 95% CI 1·8-14·86, respectively). Chronic neurological disease was a predictor of admission to PICU (OR 2·30, 95% CI 1·14-4·61).
  
  
  CONCLUSIONS
  During the 2009 pandemic, influenza was a major cause of hospitalisation in tertiary paediatric hospitals. Co-infection and underlying chronic disease increased risk of PICU admission and/or ventilation. Half the children admitted were previously healthy, supporting a role for universal influenza vaccination in children.
authors.affiliation: The Discipline of Paediatrics and Child Health, The University of Sydney, Sydney, NSW, Australia; National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, The Children's Hospital at Westmead, Sydney, NSW, Australia; The Marie Bashir Institute for Infectious Diseases and Biosecurity (MBI), Sydney Medical School, the University of Sydney, Sydney, NSW, Australia.
authors.forename: Gulam
authors.initials: G
authors.lastname: Khandaker
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Zurynski
authors.forename: Greta
authors.initials: G
authors.lastname: Ridley
authors.forename: Jim
authors.initials: J
authors.lastname: Buttery
authors.forename: Helen
authors.initials: H
authors.lastname: Marshall
authors.forename: Peter C
authors.initials: PC
authors.lastname: Richmond
authors.forename: Jenny
authors.initials: J
authors.lastname: Royle
authors.forename: Michael
authors.initials: M
authors.lastname: Gold
authors.forename: Tony
authors.initials: T
authors.lastname: Walls
authors.forename: Bruce
authors.initials: B
authors.lastname: Whitehead
authors.forename: Peter
authors.initials: P
authors.lastname: McIntyre
authors.forename: Nicholas
authors.initials: N
authors.lastname: Wood
authors.forename: Robert
authors.initials: R
authors.lastname: Booy
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Elliott
mesh_terms: D000293:Adolescent; D001315:Australia; D002648:Child; D002675:Child, Preschool; D005260:Female; D006776:Hospitals, Pediatric; 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; D011379:Prognosis; D011446:Prospective Studies; D012307:Risk Factors; D062606:Tertiary Care Centers; D016896:Treatment Outcome
keywords: Children; influenza; influenza A(H1N1)pdm09; outcome; pandemic