title: Phylogenetic analysis of hepatitis B virus full-length genomes reveals evidence for a large nosocomial outbreak in Belgium.
abstract: BACKGROUND
  Hepatitis B virus (HBV) is primarily transmitted from mother to child, by sexual contact, intravenous drug abuse, or unsafe health care-related injection practices. Despite increased safety efforts, nosocomial acquired hepatitis B infection remains problematic.
  
  
  OBJECTIVE
  A large HBV outbreak was investigated comprising 36 patients with acute HBV infection in a primary care physician's practice.
  
  
  METHODS
  In a retrospective study (2003-2008), 36 serum samples from patients with acute HBV infection were collected. They had received several injections by the same physician at least 3 months before the onset of clinical symptoms. As a control group, sera were collected from HBV patients from other physicians from the same province. Full-length HBV genomes were amplified and were phylogenetically analysed.
  
  
  RESULTS
  HBV complete genomes of 32 patients were successfully amplified and sequenced, and clustered together with the reference genotype A, subgenotype A2 strains. We also analysed 26 control HBV genotype A samples. All 32 HBV strains from the patient group clustered in a monophyletic branch with a bootstrap value of 100, whereas the control samples branched separately in another clade. The genetic distance value showed small differences within the patients group, whereas the rate within the control group was seven times higher. These observations confirm that the source of transmission was clearly different in both groups.
  
  
  CONCLUSIONS
  Maximum likelihood analysis and genetic distance calculations based on the full-length genomes of HBV strains isolated from patients and controls provided strong evidence for a common nosocomial source of infection for all 32 patient cases.
authors.affiliation: Laboratory of Clinical Virology, Rega Institute for Medical Research, Leuven, Belgium.
authors.forename: Mahmoud Reza
authors.initials: MR
authors.lastname: Pourkarim
authors.forename: Jannick
authors.initials: J
authors.lastname: Verbeeck
authors.forename: Mustafizur
authors.initials: M
authors.lastname: Rahman
authors.forename: Samad
authors.initials: S
authors.lastname: Amini-Bavil-Olyaee
authors.forename: An-Marie
authors.initials: AM
authors.lastname: Forier
authors.forename: Philippe
authors.initials: P
authors.lastname: Lemey
authors.forename: Piet
authors.initials: P
authors.lastname: Maes
authors.forename: Marc
authors.initials: M
authors.lastname: Van Ranst
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001530:Belgium / Q000453:epidemiology; D016000:Cluster Analysis; D003428:Cross Infection / Q000453:epidemiology* / Q000821:virology; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics; D004196:Disease Outbreaks; D005260:Female; D016679:Genome, Viral; D005838:Genotype; D006509:Hepatitis B / Q000453:epidemiology* / Q000821:virology; D006515:Hepatitis B virus / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D012189:Retrospective Studies; D017422:Sequence Analysis, DNA; D017385:Sequence Homology
chemical_list: D004279:DNA, Viral