title: Molecular characterization of influenza A(H1N1)pdm09 virus circulating during the 2009 outbreak in Thua Thien Hue, Vietnam.
abstract: BACKGROUND
  The influenza A(H1N1)pdm09 virus arrived in Vietnam in May 2009 via the United States and rapidly spread throughout the country. This study provides data on the viral diagnosis and molecular epidemiology of influenza A(H1N1)pdm09 virus isolated in Thua Thien Hue Province, central Vietnam.
  
  
  METHODS
  Nasopharyngeal swabs and throat swabs from 53 clinically infected patients in the peak of the outbreak were processed for viral diagnosis by culture and RT-PCR. Sequencing of entire HA and NA genes of representative isolates and molecular epidemiological analysis were performed.
  
  
  RESULTS
  A total of 32 patients were positive for influenza A virus by virus culture and/or RT-PCR; of these 22 were positive both by viral isolation and RT-PCR, 2 only by virus culture and 8 only by RT-PCR. The novel subtype of influenza A(H1N1)pdm09 was present in 93.4% of the isolates. Phylogenetic analysis of the HA and NA gene sequences showed identities higher than 99.50% in both genes. They were also similar to reference isolates in HA sequences (>99% identity) and in NA sequences (>98.50% identity). Amino acid sequences predicted for the HA gene were highly identical to reference strains. The NA amino acid substitutions identified did not include the oseltamivir-resistant H275Y substitution.
  
  
  CONCLUSIONS
  viral isolation and RT-PCR together were useful for diagnosis of the influenza A(H1N1)pdm09 virus. Variations in HA and NA sequences are similar to those identified in worldwide reference isolates and no drug resistance was found.
authors.affiliation: Department of Microbiology, Hue University of Medicine and Pharmacy, Thua Thien Hue, Vietnam. levanan_hump@yahoo.com
authors.forename: Le Van
authors.initials: le V
authors.lastname: An
authors.forename: Le Thi
authors.initials: le T
authors.lastname: Bao Chi
authors.forename: Nguyen Hoang
authors.initials: NH
authors.lastname: Bach
authors.forename: Huynh Thi
authors.initials: HT
authors.lastname: Hai Duong
authors.forename: Massimo
authors.initials: M
authors.lastname: Deligios
authors.forename: Alberto
authors.initials: A
authors.lastname: Alberti
authors.forename: Piero
authors.initials: P
authors.lastname: Cappuccinelli
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D005260:Female; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics* / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology*; D008297:Male; D008969:Molecular Sequence Data; D009305:Nasopharynx / Q000821:virology; D009439:Neuraminidase / Q000235:genetics; D058873:Pandemics; D010802:Phylogeny; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014744:Vietnam; D014764:Viral Proteins / Q000235:genetics; D014776:Virus Cultivation; D055815:Young Adult
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D014764:Viral Proteins; C487630:NA protein, influenza A virus; D009439:Neuraminidase