title: [Influenza surveillance from 1999 to 2005 in Liaoning regions].
abstract: OBJECTIVE
  To investigate the prevalence and subtypes of influenza viruses in Liaoning regions from November 1999 to March 2005.
  
  
  METHODS
  Influenza virus was isolated by embryonated eggs together with cell culture and subtypes, identified by HI test.
  
  
  RESULTS
  During the study in 1999 - 2005, a total number of 2713 swab specimens were collected in different cities in Liaoning regions in which 188 strains were identified for influenza viruses with an average rate as 7.0%. A total number of 1466 swab specimens were collected by both Centers for Disease Control and Prevention in Dalian city and Liaoning province, and 167 strains were identified positive with an average rate of 11.4%. Influenza A3, A1 and B/Yamagata all appeared before March 2002 which were predominant strains. However, since then Influenza A1 has never appeared again in Liaoning regions and B showed some changes, from Yamagata to Victoria, the characteristics on the prevalence of influenza appeared only in the period of November to February.
  
  
  CONCLUSIONS
  It was meaningful to analyze the surveillance data of influenza in different years in Liaoning regions in order to better understand the characteristics of influenza and the shifting of subtype.
authors.affiliation: Liaoning Province Center for Disease Control and Prevention, Shenyang 110005, China.
authors.forename: Shao-hui
authors.initials: SH
authors.lastname: Wu
authors.forename: Wei
authors.initials: W
authors.lastname: Yu
authors.forename: Mei-mei
authors.initials: MM
authors.lastname: Zhang
authors.forename: Jian-qiu
authors.initials: JQ
authors.lastname: Cui
authors.forename: Rong-hua
authors.initials: RH
authors.lastname: Fu
authors.forename: Xiao-guang
authors.initials: XG
authors.lastname: Zhao
authors.forename: Ya-hui
authors.initials: YH
authors.lastname: He
mesh_terms: D002681:China / Q000453:epidemiology; D006801:Humans; D009980:Influenza A virus / Q000145:classification / Q000302:isolation & purification*; D009981:Influenza B virus / Q000145:classification / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology*; D011159:Population Surveillance; D012621:Seasons