title: Clinical and radiological features of pandemic H1N1 2009 influenza virus infection manifesting as acute febrile respiratory illness at their initial presentations: comparison with contemporaneous non-H1N1 patients.
abstract: BACKGROUND
  Since the first outbreak caused by the pandemic H1N1 2009 influenza in Mexico, the virus has spread widely across the world with meaningful morbidity and mortality. However, there are few data on the comparative investigations to assess the clinical and radiological features between the H1N1 patient and non-H1N1 patients.
  
  
  OBJECTIVE
  To assess the clinical and radiological features of patients infected by the pandemic H1N1 2009 flu virus at their initial presentation and to compare them with contemporaneous non-H1N1 patients with acute febrile respiratory illness.
  
  
  METHODS
  This retrospective study was approved by the ethics committee of the Armed Forces Medical Command, South Korea. From August to September 2009, 337 consecutive patients presented with an acute febrile respiratory illness in a tertiary military hospital. Reverse-transcriptase polymerase-chain-reaction tests were performed in 62 of these patients under the impression of H1N1 infection. Clinical and radiological features at their initial presentation were described for the H1N1 group (n = 35) and non-H1N1 group (n = 27) and compared between the two groups.
  
  
  RESULTS
  Increased C-reactive protein level (97%) without leukocytosis (9%) or increased erythrocyte sedimentation rate (0%) was common in the H1N1 group at their initial presentation. On chest radiographs, 12 of 35 (34%) H1N1 patients had abnormal findings; nodules in 10 patients (83%) and consolidations in two (17%). Of the 28 H1N1 patients who underwent thin-section CT 16 patients (57%) showed abnormal findings; ground-glass opacities (GGOs) in 15 (94%), and nodules in 13 (81%). However, there were no significant differences between the H1N1 group and non-H1N1 group in terms of symptoms, laboratory results, or radiological findings (P > 0.05).
  
  
  CONCLUSIONS
  Patients with H1N1 infection show consistent clinical and radiological features at their initial presentation, however, clinical and radiological features of the H1N1 group are not significantly different from those of the non-H1N1 group.
authors.affiliation: Department of Radiology, Armed Force Byukjae Hospital, Gyeonggi-do, Korea.
authors.forename: Tae Jin
authors.initials: TJ
authors.lastname: Yun
authors.forename: Chang Min
authors.initials: CM
authors.lastname: Park
authors.forename: Gu Jin
authors.initials: GJ
authors.lastname: Kwon
authors.forename: Sung Koo
authors.initials: SK
authors.lastname: Woo
authors.forename: Seung Hoon
authors.initials: SH
authors.lastname: Park
authors.forename: Seung Hong
authors.initials: SH
authors.lastname: Choi
authors.forename: Hyun Ju
authors.initials: HJ
authors.lastname: Lee
authors.forename: Jin Mo
authors.initials: JM
authors.lastname: Goo
mesh_terms: D000208:Acute Disease; D001799:Blood Sedimentation; D002097:C-Reactive Protein / Q000032:analysis; D005334:Fever; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000000981:diagnostic imaging* / Q000453:epidemiology; D008297:Male; D058873:Pandemics; D013902:Radiography, Thoracic; D056910:Republic of Korea / Q000453:epidemiology; D012140:Respiratory Tract Diseases / Q000000981:diagnostic imaging; D012189:Retrospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014057:Tomography, X-Ray Computed; D055815:Young Adult
chemical_list: D002097:C-Reactive Protein