title: Pandemic influenza A (H1N1) virus in households with young children.
abstract: BACKGROUND
  Influenza viruses may cause a severe infection in infants and young children. The transmission patterns of pandemic 2009 influenza A (H1N1) within households with young children are poorly characterized.
  
  
  METHODS
  Household members of six children younger than 1·5 years with documented 2009 influenza A (H1N1) infection were studied by daily symptom diaries and serial parent-collected nasal swab samples for detection of influenza A by reverse transcription polymerase chain reaction (RT-PCR) assay.
  
  
  RESULTS
  Laboratory-confirmed, symptomatic influenza was documented in 11 of 15 household contacts of young children with pandemic influenza (73%; 95% CI, 48-99). In five contact cases symptoms started earlier, in three cases on the same day, and in three cases after the onset of symptoms in the youngest child. The first case with influenza A (H1N1) within the household was an elder sibling in two households, father in two households, the youngest child in one household, and the youngest child at the same time with a sibling in one household. The median copy number of influenza virus was higher in children than in adults (4·2 × 10(7) versus 4·9 × 10(4), P = 0·02).
  
  
  CONCLUSIONS
  This study demonstrates the feasibility of nasal swab sampling by parents in investigation of household transmission of influenza. The results support influenza vaccination of all household contacts of young children.
authors.affiliation: Department of Pediatrics, Turku University Hospital, Turku, Finland. ville.peltola@utu.fi
authors.forename: Ville
authors.initials: V
authors.lastname: Peltola
authors.forename: Tamara
authors.initials: T
authors.lastname: Teros-Jaakkola
authors.forename: Maris
authors.initials: M
authors.lastname: Rulli
authors.forename: Laura
authors.initials: L
authors.lastname: Toivonen
authors.forename: Eeva
authors.initials: E
authors.lastname: Broberg
authors.forename: Matti
authors.initials: M
authors.lastname: Waris
authors.forename: Jussi
authors.initials: J
authors.lastname: Mertsola
mesh_terms: D002675:Child, Preschool; D015331:Cohort Studies; D005191:Family Characteristics; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D007251:Influenza, Human / Q000453:epidemiology / Q000635:transmission* / Q000821:virology*; D008297:Male; D058873:Pandemics