title: Influenza infection in the intensive care unit: Four years after the 2009 pandemic.
abstract: The role of influenza viruses in severe acute respiratory infection (SARI) in Intensive Care Units (ICU) remains unknown. The post-pandemic influenza A(H1N1)pdm09 period, in particular, has been poorly studied.
  
  
  OBJECTIVE
  To identify influenza SARI patients in ICU, to assess the usefulness of the symptoms of influenza-like illness (ILI), and to compare the features of pandemic vs. post-pandemic influenza A(H1N1) pdm09 infection.
  
  
  METHODS
  A prospective observational study with SARI patients admitted to ICU during the first three post-pandemic seasons. Patient demographics, characteristics and outcomes were recorded. An influenza epidemic period (IEP) was defined as >100 cases/100,000 inhabitants per week.
  
  
  RESULTS
  One hundred sixty-three patients were diagnosed with SARI. ILI was present in 65 (39.9%) patients. Influenza infection was documented in 41 patients, 27 (41.5%) ILI patients, and 14 (14.3%) non-ILI patients, 27 of them during an IEP. Influenza A viruses were mainly responsible. Only five patients had influenza B virus infection, which were non-ILI during an IEP. SARI overall mortality was 22.1%, and 15% in influenza infection patients. Pandemic and post-pandemic influenza infection patients shared similar clinical features.
  
  
  CONCLUSIONS
  During influenza epidemic periods, influenza infection screening should be considered in all SARI patients. Influenza SARI was mainly caused by subtype A(H1N1)pdm09 and A(H3N2) in post-pandemic seasons, and no differences were observed in ILI and mortality rate compared with a pandemic season.
authors.affiliation: Critical Care Department, Vall d'Hebron University Hospital, Vall d'Hebron Research Institute (VHIR), Universitat Autònoma de Barcelona (UAB), Spain. Electronic address: marperez@vhebron.net.
authors.forename: Marcos
authors.initials: M
authors.lastname: Pérez-Carrasco
authors.affiliation: Critical Care Department, Vall d'Hebron University Hospital, Vall d'Hebron Research Institute (VHIR), Universitat Autònoma de Barcelona (UAB), Spain.
authors.forename: Leonel
authors.initials: L
authors.lastname: Lagunes
authors.affiliation: Department of Microbiology, Vall d'Hebron University Hospital, Barcelona, Spain.
authors.forename: Andrés
authors.initials: A
authors.lastname: Antón
authors.affiliation: Critical Care Department, Vall d'Hebron University Hospital, Vall d'Hebron Research Institute (VHIR), Universitat Autònoma de Barcelona (UAB), Spain.
authors.forename: Simone
authors.initials: S
authors.lastname: Gattarello
authors.affiliation: Critical Care Department, Vall d'Hebron University Hospital, Vall d'Hebron Research Institute (VHIR), Universitat Autònoma de Barcelona (UAB), Spain.
authors.forename: César
authors.initials: C
authors.lastname: Laborda
authors.affiliation: Department of Microbiology, Vall d'Hebron University Hospital, Barcelona, Spain.
authors.forename: Tomás
authors.initials: T
authors.lastname: Pumarola
authors.affiliation: Critical Care Department, Vall d'Hebron University Hospital, Vall d'Hebron Research Institute (VHIR), Universitat Autònoma de Barcelona (UAB), Spain; Centro de Investigación Biomédica en Red: Enfermedades Respiratorias (CIBERes), Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Rello
mesh_terms: D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D053122:Influenza A Virus, H3N2 Subtype; D009981:Influenza B virus; D007251:Influenza, Human / Q000453:epidemiology*; D007362:Intensive Care Units; D058873:Pandemics; D011446:Prospective Studies; D012621:Seasons; D013030:Spain / Q000453:epidemiology; D062606:Tertiary Care Centers
keywords: A (H1N1) pdm09; A(H1N1)pdm09; Acute respiratory failure; Enfermedad tipo gripe; Infección respiratoria aguda grave; Influenza A virus; Influenza-like illness; Insuficiencia respiratoria aguda; Severe acute respiratory infection; Virus de la gripe A