title: [Analysis of etiology of four pandemic influenza A (H1N1) virus outbreaks in Shandong province, in 2009].
abstract: OBJECTIVE
  To isolate and identify the influenza virus that caused four influenza-like-illness outbreaks in Jining city of Shandong Province in 2009 and analyze the genetic characteristics of hemagglutinin (HA) and neuraminidase (NA) gene, the variation of these genes were studied.
  
  
  METHODS
  34 nasopharyngeal swabs from fever patients of four influenza-like-illness outbreaks were collected and diagnosed by real time quantitative RT-PCR method. The positive samples were incubated and cultured for virus. HA and NA genes of isolated pandemic influenza A (H1N1) virus were sequenced, the homology analysis was done with DNAStar software and the genetic evolution and amino acid substitutions were performed with Mega 4.0 software. The sequences were compared with WHO recommended vaccine virus, native reference virus.
  
  
  RESULTS
  Seventeen of 34 nasopharyngeal swabs were positive, 11 pandemic influenza A (H1N1) viruses were isolated and HA and NA genes of 7 strains were sequenced. Phylogenetic analysis for hemagglutinin and neuraminidase gene of Shandong outbreak strains showed that there were 98.4% - 99.6% and 99.2% - 100.0% sequence identity. Compared with WHO-recommended vaccine strain, the reference virus in mainland China strain, eleven amino acids were changed for HA protein, including position 38, 40, 56, 90, 100, 145, 172, 173, 220, 303 and 338, and 38, 40, 303 of HA protein were located in the antigenic determination C cluster, 172, 173 in the D cluster, 56 in the E cluster, site 40 of HA protein were glycosylated. In NA protein, seven amino acids were changed, including position 80, 106, 241, 248, 351, 369 and 386, site 40 of NA protein were glycosylated. No mutations of 275 in NA protein were found.
  
  
  CONCLUSIONS
  The HA and NA genes of the epidemic strains showed high homology, some mutations in the HA and NA proteins were found, the antigenic site and glycosylation site of some strains were changed during the epidemic process.
authors.affiliation: Shandong Center for Disease Control and Prevention, Key Lab of Infectious Diseases in Shandong Province, Shandong University Institute for Prevention Medicine, Jinan 250014, China. sdlz01@yahoo.com.cn
authors.forename: Zhong
authors.initials: Z
authors.lastname: Li
authors.forename: Ti
authors.initials: T
authors.lastname: Liu
authors.forename: Yi
authors.initials: Y
authors.lastname: Lin
authors.forename: Sheng-Yang
authors.initials: SY
authors.lastname: Zhang
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Wen-Guo
authors.initials: WG
authors.lastname: Jiang
authors.forename: Xian-Jun
authors.initials: XJ
authors.lastname: Wang
authors.forename: Ai-Qiang
authors.initials: AQ
authors.lastname: Xu
authors.forename: Zhen-Qiang
authors.initials: ZQ
authors.lastname: Bi
mesh_terms: D002681:China / Q000453:epidemiology; D004196:Disease Outbreaks; D006031:Glycosylation; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology / Q000821:virology*; D009439:Neuraminidase / Q000235:genetics
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D009439:Neuraminidase