title: Influenza in the immediate post-pandemic era: a comparison with seasonal and pandemic influenza in hospitalized patients.
abstract: BACKGROUND
  Comparative data on severity and treatment of seasonal, pandemic and post-pandemic influenza virus infections are scarce.
  
  
  OBJECTIVE
  To systematically analyze characteristics of hospitalized patients with influenza in the post-pandemic period compared to seasonal and pandemic influenza.
  
  
  METHODS
  Clinical and virological data of patients hospitalized in a tertiary referral hospital with post-pandemic influenza (2010-2011) were compared with those during seasonal influenza epidemics (2007-2009) and the influenza A(H1N1)pdm09 pandemic (2009-2010).
  
  
  RESULTS
  82 patients were admitted during the post-pandemic period, compared to 85 during the pandemic and 60 during seasonal influenza epidemics. No differences were observed in the occurrence of complicated illness and the need for intensive care. However, radiographic pneumonia was significantly more often diagnosed in patients with influenza A(H1N1)pdm09 compared to patients with seasonal influenza A (25% versus 71% in pandemic, p=0.004, and 55% in post-pandemic, p=0.047). Oseltamivir was more frequently prescribed in post-pandemic and pandemic patients compared to previous influenza seasons (48.9% resp. 76.5% versus 6.5%, p<0.0001). During the post-pandemic period, patients with influenza B were significantly less often treated with oseltamivir compared to patients with influenza A (27.0% versus 48.9%, p=0.043), although the course of illness in patients with influenza B was comparable with influenza A. No upsurge of oseltamivir resistance was observed.
  
  
  CONCLUSIONS
  In our center, severity of illness was comparable for all influenza seasons, although more radiographic pneumonia was diagnosed in patients with influenza A(H1N1)pdm09. Despite the increased use of oseltamivir, no increase in oseltamivir resistance was detected.
authors.affiliation: Department of Medical Microbiology, Division of Clinical Virology, University of Groningen, University Medical Center Groningen, The Netherlands. j.c.rahamat@umcg.nl
authors.forename: J C
authors.initials: JC
authors.lastname: Rahamat-Langendoen
authors.forename: E D
authors.initials: ED
authors.lastname: Tutuhatunewa
authors.forename: E H
authors.initials: EH
authors.lastname: Schölvinck
authors.forename: E
authors.initials: E
authors.lastname: Hak
authors.forename: M
authors.initials: M
authors.lastname: Koopmans
authors.forename: H G M
authors.initials: HG
authors.lastname: Niesters
authors.forename: A
authors.initials: A
authors.lastname: Riezebos-Brilman
mesh_terms: D000293:Adolescent; D000328:Adult; D000998:Antiviral Agents / Q000008:administration & dosage; D024882:Drug Resistance, Viral; D005260:Female; D006801:Humans; D007251:Influenza, Human / Q000150:complications / Q000188:drug therapy / Q000473:pathology* / Q000821:virology*; D007297:Inpatients; D008297:Male; D008875:Middle Aged; D009975:Orthomyxoviridae / Q000145:classification* / Q000187:drug effects / Q000302:isolation & purification / Q000472:pathogenicity*; D053139:Oseltamivir / Q000008:administration & dosage; D011014:Pneumonia / Q000175:diagnosis / Q000453:epidemiology; D012189:Retrospective Studies; D012720:Severity of Illness Index; D055815:Young Adult
chemical_list: D000998:Antiviral Agents; D053139:Oseltamivir