title: Different features of influenza A H1N1pdm09 virus infection among adults in 2009/10 and 2010/11.
abstract: BACKGROUND
  Influenza A H1N1pdm09 virus infection causes an epidemiologically and clinically severe disease mostly characterized by pneumonia, resulting in a high mortality rate. The purpose of this study was to investigate and compare epidemiological and clinical characteristics of influenza A H1N1pdm09 virus infection in patients hospitalized during the pandemic (2009/10) and post-pandemic seasons (2010/11).
  
  
  METHODS
  The data of patients with laboratory-confirmed influenza A H1N1pdm09 virus infection hospitalized and treated at the University Hospital for Infectious Diseases Dr. Fran Mihaljevic in Zagreb, Croatia in the first two seasons of appearance were analyzed.
  
  
  RESULTS
  Compared to the pandemic season, in the post-pandemic season, patients were hospitalized longer, had higher values of inflammatory parameters, and were more often treated with antibiotics. The total number of risk factors in patients did not vary significantly between the two seasons. In the pandemic season, a significantly higher number of obese patients and patients with chronic lung disease was observed, whereas in the post-pandemic season, a statistically significant number of patients presented with symptoms of chronic cardiac and neuromuscular diseases. Primary viral pneumonia was frequently registered in younger adults during the pandemic season, whereas in the post-pandemic season, there were more cases of bacterial pneumonia.
  
  
  CONCLUSIONS
  During the pandemic season, the influenza A H1N1pdm09 virus infection caused a severe disease with rare bacterial complications, especially in adult patients. The common characteristics of the influenza A H1N1pdm09 virus were lost in the post-pandemic season, assuming the shape and characteristics of the seasonal influenza A virus.
authors.affiliation: University Hospital Mostar, Mostar, Bosnia and Herzegovina. svjetlanag@gmail.com.
authors.forename: Svjetlana
authors.initials: S
authors.lastname: Grgic
authors.forename: Sinisa
authors.initials: S
authors.lastname: Skocibusic
authors.forename: Elvira
authors.initials: E
authors.lastname: Celjuska-Tosev
authors.forename: Jadranka
authors.initials: J
authors.lastname: Nikolic
authors.forename: Jurica
authors.initials: J
authors.lastname: Arapovic
authors.forename: Ilija
authors.initials: I
authors.lastname: Kuzman
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017523:Croatia; D005260:Female; D006760:Hospitalization; D006785:Hospitals, University; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000473:pathology* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D055815:Young Adult