title: Genetic drift of norovirus genotype GII-4 in seven consecutive epidemic seasons in Hungary.
abstract: BACKGROUND
  Noroviruses are common pathogens in human gastroenteritis outbreaks worldwide. They belong to a genetically diverse group of RNA viruses with multiple genogroups (G) and genotypes. Genotype GII-4 norovirus (Lordsdale) is the predominant agent in epidemics.
  
  
  OBJECTIVE
  To investigate the genetic variation in GII-4 strains isolated during seven epidemic seasons in Hungary from November 2000 to June 2007.
  
  
  METHODS
  Using the prospective epidemiological surveillance of norovirus outbreaks in Hungary, GII-4 strains were selected for further genetic analysis. After phylogenetic analysis, RNA-polymerase (open reading frame 1; ORF1), capsid (ORF2) and the ORF1/ORF2 junction were analysed by RT-PCR and sequencing.
  
  
  RESULTS
  Three hundred and seventy-seven (76.8%) of 491 confirmed norovirus outbreaks were caused by genotype GII-4. GII-4 was the predominant genotype in six of the seven epidemic seasons. Four main GII-4 variants--epidemic point mutants--(GII-4-2000, GII-4-2002, GII-4-2004 and GII-4-2006b) were detected, with each variant predominating in two consecutive epidemic seasons.
  
  
  CONCLUSIONS
  Genotype GII-4 was confirmed as the predominant genetic type in epidemic norovirus seasons in Hungary. Genetic drift successfully promotes the re-emergence of GII-4 variants in the population. The elevated number of norovirus outbreaks in the population predicts the emergence of new GII-4 genetic variants as part of an international epidemic.
authors.affiliation: Regional Laboratory of Virology, ANTSZ Regional Institute of State Public Health Service, Szabadság út 7, H-7623 Pécs, Hungary. reuter.gabor@baranya.antsz.hu
authors.forename: Gábor
authors.initials: G
authors.lastname: Reuter
authors.forename: Péter
authors.initials: P
authors.lastname: Pankovics
authors.forename: György
authors.initials: G
authors.lastname: Szucs
mesh_terms: D017250:Caliciviridae Infections / Q000453:epidemiology* / Q000821:virology; D004196:Disease Outbreaks; D005759:Gastroenteritis / Q000453:epidemiology* / Q000821:virology; D040961:Genetic Drift; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D006814:Hungary / Q000453:epidemiology; D029322:Norovirus / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D010802:Phylogeny