title: Clinical differences between influenza A (H1N1) virus and respiratory infection between the two waves in 2009 and 2010.
abstract: BACKGROUND
  The purpose of the present retrospective study was to examine the clinical differences between patients hospitalized with H1N1 virus and those hospitalized with nonvirus respiratory tract infection in 2009 and 2010.
  
  
  METHODS
  Adult patient data were collected from three tertiary hospital centers. Real-time reverse transcriptase polymerase chain reaction testing was used to confirm the diagnosis. We included 106 H1N1-positive patients (52 from 2009 and 54 from 2010). These data were compared with those from 108 patients with H1N1-negative respiratory tract infection (51 patients from 2009 and 57 from 2010).
  
  
  RESULTS
  In 2009, the mean age was 36.4 years for H1N1-positive patients versus 46.4 years for H1N1-negative patients, and mean body mass index (BMI) was 26.4 kg/m(2) patients and 28.1 kg/m(2), respectively. In 2009, seven patients required intubation, six of whom were H1N1-positive. In 2010, the mean age was 43.8 years for H1N1-positive patients versus 60.2 years for H1N1-negative patients, and mean BMI was 32.3 kg/m(2) and 26.9 kg/m(2), respectively. In 2010, six patients required intubation, three of whom were H1N1-positive. Abnormal chest x-ray findings were found significantly more frequently in H1N1-negative patients than in H1N1-positive patients.
  
  
  CONCLUSIONS
  In comparison with 2009, H1N1-positive patients in 2010 were older, were more likely to be obese, and had more severe clinical and laboratory perturbations. However, this did not affect their outcomes. H1N1-negative patients were older in comparison with those who were H1N1-positive, and had more severe clinical and laboratory perturbations.
authors.affiliation: Unit of Infectious Diseases, General University Hospital of Alexandroupolis, Democritus University of Thrace, Komotini.
authors.forename: Paul
authors.initials: P
authors.lastname: Zarogoulidis
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Glaros
authors.forename: Ioannis
authors.initials: I
authors.lastname: Kioumis
authors.forename: Eirini
authors.initials: E
authors.lastname: Terzi
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Porpodis
authors.forename: Anastasios
authors.initials: A
authors.lastname: Tsiotsios
authors.forename: Anastasios
authors.initials: A
authors.lastname: Kallianos
authors.forename: Georgia
authors.initials: G
authors.lastname: Trakada
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Machairiotis
authors.forename: Aikaterini
authors.initials: A
authors.lastname: Stylianaki
authors.forename: Antonis
authors.initials: A
authors.lastname: Sakas
authors.forename: Ageliki
authors.initials: A
authors.lastname: Rapti
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Courcoutsakis
authors.forename: Theodoros C
authors.initials: TC
authors.lastname: Constantinidis
authors.forename: Efstartios
authors.initials: E
authors.lastname: Maltezos
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Zarogoulidis