title: A comparison of the demographic and clinical characteristics of laboratory-confirmed influenza B Yamagata and Victoria lineage infection.
abstract: BACKGROUND
  The evolution of influenza viruses is characterized by the co-circulation of two antigenically and genetically distinct lineages B/Victoria/2/87-like viruses (Victoria) and B/Yamagata/16/88-like viruses (Yamagata). To date, there is not much data associating lineages variation with demographic and clinical data.
  
  
  OBJECTIVE
  We compared the demographic and clinical characteristics of patients with laboratory-confirmed influenza B Victoria or Yamagata lineage infection.
  
  
  METHODS
  We retrospectively analyzed data from 6811 patients aged from <1 through 99 years with influenza like-illness who consulted the sentinel site or sentinel hospital in the seasons 2010/2011, 2011/2012 and 2012/2013. There were 662 patients positive for influenza B virus by multiplex real-time RT-PCR. Six hundred thirty-seven (96.8%) were successfully subtyped for Victoria or Yamagata lineage infection. The available demographic and clinical data was compared.
  
  
  RESULTS
  Patients with the Victoria lineage were significantly younger compared to patients infected with the Yamagata lineage. The Victoria lineage was the predominant strain in the 15-34 age groups in patients consulting at primary care level and in hospitalized patients. In the youngest age group (0-4 years) approximately half of the confirmed influenza B cases belonged to the Victoria (55%) and the rest to the Yamagata lineage (45%). Aside from age, there was no statistically significant difference found in gender distribution, vaccination history, clinical presentation or risk factors for severe influenza infection in hospitalized patients after adjustment for the age.
  
  
  CONCLUSIONS
  The frequency of influenza B Victoria and Yamagata infection is age dependent with no significant differences detected in clinical presentation comparing both lineages.
authors.affiliation: Centre for Communicable Diseases, National Institute of Public Health, Trubarjeva 2, 1000 Ljubljana, Slovenia. Electronic address: maja.socan@nijz.si.
authors.forename: Maja
authors.initials: M
authors.lastname: Sočan
authors.affiliation: Laboratory for Public Health Virology, National Laboratory for Health, Environment and Food, Bohoričeva 15, 1000 Ljubljana, Slovenia. Electronic address: katarina.prosenc@nlzoh.si.
authors.forename: Katarina
authors.initials: K
authors.lastname: Prosenc
authors.affiliation: Centre for Communicable Diseases, National Institute of Public Health, Trubarjeva 2, 1000 Ljubljana, Slovenia. Electronic address: veronika.ucakar@nijz.si.
authors.forename: Veronika
authors.initials: V
authors.lastname: Učakar
authors.affiliation: Laboratory for Public Health Virology, National Laboratory for Health, Environment and Food, Bohoričeva 15, 1000 Ljubljana, Slovenia. Electronic address: natasa.berginc@nlzoh.si.
authors.forename: Nataša
authors.initials: N
authors.lastname: Berginc
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D003710:Demography; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D009981:Influenza B virus / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000473:pathology* / Q000821:virology; D008297:Male; D008875:Middle Aged; D060885:Multiplex Polymerase Chain Reaction; D060888:Real-Time Polymerase Chain Reaction; D012189:Retrospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055815:Young Adult
keywords: Age distribution; Clinical presentation; Influenza B; Victoria lineage; Yamagata lineage