title: Seroepidemiology and phylogenetic characterisation of measles virus in Ireland, 2004-2013.
abstract: BACKGROUND
  Ireland is classified as an area of high measles incidence. A World Health Organisation-European Region strategic plan exists for measles elimination by 2015.
  
  
  OBJECTIVE
  To retrospectively investigate measles outbreaks using all patient samples (sera and oral fluid) received for measles laboratory diagnosis and characterise the genetic diversity of circulating measles genotypes in Ireland.
  
  
  METHODS
  704 cases of acute measles infection as determined by the presence of measles specific IgM in sera and oral fluids were confirmed at the National Virus Reference Laboratory. Measles positive samples (n=116) were examined by genotyping, sequence analysis and phylogenetic characterisation.
  
  
  RESULTS
  Three measles outbreaks occurred over the study period: 2004, 2009/2010 and 2011. Measles IgM positivity ranged from 22-29% in outbreak years to 5-10% in the intervening years. Age profile analysis revealed that whereas individuals >10 years accounted for only 8% of cases in the 2004 outbreak, this increased to 33% and 29% in the 2009/2010 and 2011 outbreaks, respectively. The <1 year cohort accounted for 18-20% of cases in all outbreaks. Phylogenetic analysis demonstrated both indigenous transmission and also importation events. Clade D viruses were exclusively found circulating in Ireland, with autochthonous transmission of diverse genotype D4 strains associated with large outbreaks across Europe. More recently, genotype D8 was identified and these were associated with importation events.
  
  
  CONCLUSIONS
  This study provides a comprehensive genetic analysis of circulating measles genotypes in Ireland and discriminated between indigenous and imported viral strains. Notably, an increase in laboratory-confirmed measles cases in the greater than 10 years of age group was seen over the study period. This information is valuable to inform vaccination strategies with a focus on those populations who remain susceptible to measles infection.
authors.affiliation: National Virus Reference Laboratory, School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland. Electronic address: bernadette.oriordan@ucd.ie.
authors.forename: Bernadette
authors.initials: B
authors.lastname: O' Riordan
authors.affiliation: National Virus Reference Laboratory, School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Carr
authors.affiliation: National Virus Reference Laboratory, School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Jeff
authors.initials: J
authors.lastname: Connell
authors.affiliation: National Virus Reference Laboratory, School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Linda
authors.initials: L
authors.lastname: Dunford
authors.affiliation: National Virus Reference Laboratory, School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: William W
authors.initials: WW
authors.lastname: Hall
authors.affiliation: National Virus Reference Laboratory, School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Jaythoon
authors.initials: J
authors.lastname: Hassan
mesh_terms: D000293:Adolescent; D000375:Aging; D000914:Antibodies, Viral / Q000097:blood*; D001483:Base Sequence; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005260:Female; D014644:Genetic Variation; D006801:Humans; D007075:Immunoglobulin M / Q000097:blood; D007223:Infant; D007494:Ireland / Q000453:epidemiology; D008297:Male; D008457:Measles / Q000453:epidemiology* / Q000635:transmission / Q000821:virology; D008459:Measles virus / Q000145:classification / Q000235:genetics*; D022542:Measles-Mumps-Rubella Vaccine / Q000627:therapeutic use; D010802:Phylogeny; D012367:RNA, Viral / Q000235:genetics*; D012189:Retrospective Studies; D017423:Sequence Analysis, RNA; D016036:Seroepidemiologic Studies; D014611:Vaccination; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D007075:Immunoglobulin M; D022542:Measles-Mumps-Rubella Vaccine; D012367:RNA, Viral
keywords: Ireland; Measles; Phylogenetics; Seroepidemiology