title: Chronological changes of mumps virus genotypes in Japan between 1999-2013.
abstract: BACKGROUND
  The molecular epidemiology of mumps virus (MuV) has been carried out worldwide based on genotyping proposed by the World Health Organisation. However, longitudinal molecular epidemiological studies of MuV are still limited.
  
  
  METHODS
  This study carried out genotyping of MuVs isolated in Yamagata prefecture, which is located in northern Japan, between 1999-2013, using standard nomenclature based on the sequence analysis of the entire 316 nucleotides of the small hydrophobic (SH) gene.
  
  
  RESULTS
  During this 15-year period, 249 MuVs were isolated, with the majority of them belonging to genotype G. Phylogenetic analysis revealed that genotype G strains were divided into two distinct clusters 1 and 2, consisting of 178 and 47 strains, respectively. The cluster 1 strains were isolated every year since 2001, except for 2012. The cluster 2 strains first appeared in 2011 and were dominant in 2011 and 2012. The epidemic pattern of genotype G strains observed in Yamagata was similar to those in Kanagawa and Hyogo prefectures located in eastern and western Japan, respectively. Only one L, three H and one F genotype strains were isolated in 2001, 2004 and 2010, respectively. Almost every year several genotype B strains related to Japanese vaccine strains were isolated.
  
  
  CONCLUSIONS
  These data demonstrated that the genotype G strains have been endemically perpetuating as the major type over a wide area of Japan since 2001, although the genotype G strains that emerged after 2011 differed from the earlier strains.
authors.affiliation: a Department of Microbiology , Yamagata Prefectural Institute of Public Health , Yamagata , Yamagata , Japan ;
authors.forename: Yoko
authors.initials: Y
authors.lastname: Aoki
authors.affiliation: a Department of Microbiology , Yamagata Prefectural Institute of Public Health , Yamagata , Yamagata , Japan ;
authors.forename: Yohei
authors.initials: Y
authors.lastname: Matoba
authors.affiliation: a Department of Microbiology , Yamagata Prefectural Institute of Public Health , Yamagata , Yamagata , Japan ;
authors.forename: Shizuka
authors.initials: S
authors.lastname: Tanaka
authors.affiliation: a Department of Microbiology , Yamagata Prefectural Institute of Public Health , Yamagata , Yamagata , Japan ;
authors.forename: Kazue
authors.initials: K
authors.lastname: Yahagi
authors.affiliation: b Yamanobe Pediatric Clinic , Yamanobe , Yamagata , Japan ;
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Itagaki
authors.affiliation: c Katsushima Pediatric Clinic , Yamagata , Yamagata , Japan ;
authors.forename: Fumio
authors.initials: F
authors.lastname: Katsushima
authors.affiliation: c Katsushima Pediatric Clinic , Yamagata , Yamagata , Japan ;
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Katsushima
authors.affiliation: d Department of Virology 3 , National Institute of Infectious Diseases , Tokyo , Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Takeda
authors.affiliation: a Department of Microbiology , Yamagata Prefectural Institute of Public Health , Yamagata , Yamagata , Japan ;
authors.forename: Katsumi
authors.initials: K
authors.lastname: Mizuta
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007564:Japan / Q000453:epidemiology; D008297:Male; D017720:Molecular Epidemiology; D009107:Mumps / Q000453:epidemiology* / Q000821:virology*; D009109:Mumps virus / Q000235:genetics*
keywords: Mumps virus; epidemiology; genotype; sequence