title: H1N1 influenza infection in children: Frequency, pattern, and outcome of chest radiographic abnormalities.
abstract: OBJECTIVE
  To describe the frequency, pattern, and outcome of chest radiographic abnormalities in children with H1N1 influenza infection.
  
  
  METHODS
  Three hundred and fourteen paediatric patients with confirmed H1N1 influenza infection who underwent chest radiography at presentation at a single institution during the outbreak in 2009 were retrospectively reviewed. Abnormal chest radiographic findings related to acute infection were analysed in terms of frequency, pattern, and distribution. Medical records and follow-up radiographs were also reviewed to assess clinical features and outcomes.
  
  
  RESULTS
  Chest lesions suggesting acute infection were identified in 49 (16%) patients (mean age 8.2 years, range approximately 1.8-18.5 years). The most common finding was prominent peribronchial marking (71%), followed by air-space opacity (51%) with or without volume decrease, generalized hyperinflation (24%), and pleural effusion (20%). Other minor findings included pneumomediastinum (n=2) and a nodule (n=1). Distributions were bilateral (55%) or unilateral (45%) with frequent involvement of lower (78%), and middle (59%) lung zones. Thirty-nine patients (80%) were hospitalized and six (12%) required mechanical ventilation, followed by recovery. Thirty-one out of the 33 patients that underwent follow-up radiography showed marked resolution of all radiographic abnormalities.
  
  
  CONCLUSIONS
  The frequency of a chest radiographic abnormality was found to be low in children with H1N1 influenza infection. Although typical radiographic findings of a viral lower respiratory infection were more common, unilateral involvement and air-space opacity were common, often with pleural effusion. Furthermore, pulmonary lesions showed near complete resolution on follow-up radiographs in the majority of patients.
authors.affiliation: Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: S-Y
authors.initials: SY
authors.lastname: Yoo
authors.forename: J H
authors.initials: JH
authors.lastname: Kim
authors.forename: H
authors.initials: H
authors.lastname: Eo
authors.forename: T Y
authors.initials: TY
authors.lastname: Jeon
authors.forename: K E
authors.initials: KE
authors.lastname: Shin
authors.forename: W S
authors.initials: WS
authors.lastname: Shin
authors.forename: H N
authors.initials: HN
authors.lastname: Jung
authors.forename: Y-J
authors.initials: YJ
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000000981:diagnostic imaging* / Q000453:epidemiology; D008297:Male; D015588:Observer Variation; D011859:Radiography; D012189:Retrospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016896:Treatment Outcome