title: Epidemiological dynamics and phylogeography of influenza virus in southern China.
abstract: BACKGROUND
  Understanding the epidemiological dynamics of influenza virus is central to surveillance and vaccine strain selection. It has been suggested that tropical and subtropical regions represent the global source of influenza epidemics. However, our understanding of the epidemiological dynamics of influenza virus in these regions is limited by a relative lack of long-term data.
  
  
  METHODS
  We analyzed epidemiological and virological data on influenza recorded over a period of 15 years from the metropolitan city of Shenzhen in subtropical southern China. We used wavelet analysis to determine the periodicity of influenza epidemics and molecular phylogeographic analysis to investigate the role of Shenzhen and southern China in the global evolution of influenza virus.
  
  
  RESULTS
  We show that southern China is unlikely to represent an epicenter of global influenza activity, because activity in Shenzhen is characterized by significant annual cycles, multiple viral introductions every year, limited persistence across epidemic seasons, and viruses that generally are not positioned on the trunk of the global influenza virus phylogeny.
  
  
  CONCLUSIONS
  We propose that novel influenza viruses emerge and evolve in multiple geographic localities and that the global evolution of influenza virus is complex and does not simply originate from a southern Chinese epicenter.
authors.affiliation: Shenzhen Center for Disease Control and Prevention, Shenzhen, Guangdong, China.
authors.forename: Xiaowen
authors.initials: X
authors.lastname: Cheng
authors.forename: Yi
authors.initials: Y
authors.lastname: Tan
authors.forename: Mingliang
authors.initials: M
authors.lastname: He
authors.forename: Tommy Tsan-Yuk
authors.initials: TT
authors.lastname: Lam
authors.forename: Xing
authors.initials: X
authors.lastname: Lu
authors.forename: Cécile
authors.initials: C
authors.lastname: Viboud
authors.forename: Jianfan
authors.initials: J
authors.lastname: He
authors.forename: Shunxiang
authors.initials: S
authors.lastname: Zhang
authors.forename: Jianhua
authors.initials: J
authors.lastname: Lu
authors.forename: Chunli
authors.initials: C
authors.lastname: Wu
authors.forename: Shishong
authors.initials: S
authors.lastname: Fang
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.forename: Xu
authors.initials: X
authors.lastname: Xie
authors.forename: Hanwu
authors.initials: H
authors.lastname: Ma
authors.forename: Martha I
authors.initials: MI
authors.lastname: Nelson
authors.forename: Hsiang-fu
authors.initials: HF
authors.lastname: Kung
authors.forename: Edward C
authors.initials: EC
authors.lastname: Holmes
authors.forename: Jinquan
authors.initials: J
authors.lastname: Cheng
mesh_terms: D000818:Animals; D002642:Chick Embryo; D002681:China / Q000453:epidemiology; D004285:Dogs; D058872:Epidemics; D019143:Evolution, Molecular; D006801:Humans; D009980:Influenza A virus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D009981:Influenza B virus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control / Q000821:virology; D061985:Madin Darby Canine Kidney Cells; D008969:Molecular Sequence Data; D010507:Periodicity; D010802:Phylogeny; D058974:Phylogeography; D012621:Seasons