title: Epidemiology and seroepidemiology of human enterovirus 71 among Thai populations.
abstract: BACKGROUND
  Human enterovirus 71 (EV71) is an important pathogen caused large outbreaks in Asian-Pacific region with severe neurological complications and may lead to death in young children. Understanding of the etiological spectrum and epidemic changes of enterovirus and population's immunity against EV71 are crucial for the implementation of future therapeutic and prophylactic intervention.
  
  
  RESULTS
  A total of 1,182 patients who presented with the symptoms of hand foot and mouth disease (67.3%) or herpangina (HA) (16.7%) and admitted to the hospitals during 2008-2013 were tested for enterovirus using pan-enterovirus PCR targeting 5'-untranslated region and specific PCR for viral capsid protein 1 gene. Overall, 59.7% were pan-enterovirus positive comprising 9.1% EV71 and 31.2% coxsackievirus species A (CV-A) including 70.5% CV-A6, 27.6% CV-A16, 1.1% CV-A10, and 0.8% CV-A5. HFMD and HA occurred endemically during 2008-2011. The number of cases increased dramatically in June 2012 with the percentage of the recently emerged CV-A6 significantly rose to 28.4%. Co-circulation between different EV71 genotypes was observed during the outbreak. Total of 161 sera obtained from healthy individuals were tested for neutralizing antibodies (NAb) against EV71 subgenotype B5 (EV71-B5) using microneutralization assay. The seropositive rate of EV71-B5 was 65.8%. The age-adjusted seroprevalence for individuals was found to be lowest in children aged >6 months to 2 years (42.5%). The seropositive rate remained relatively low in preschool children aged > 2 years to 6 years (48.3%) and thereafter increased sharply to more than 80% in individuals aged > 6 years.
  
  
  CONCLUSIONS
  This study describes longitudinal data reflecting changing patterns of enterovirus prevalence over 6 years and demonstrates high seroprevalences of EV71-B5 NAb among Thai individuals. The rate of EV71 seropositive increased with age but without gender-specific significant difference. We identified that relative lower EV71 seropositive rate in early 2012 may demonstrate widely presented of EV71-B5 in the population before account for a large outbreak scale epidemic occurred in 2012 with due to a relatively high susceptibility of the younger population.
authors.forename: Piyada
authors.initials: P
authors.lastname: Linsuwanon
authors.forename: Jiratchaya
authors.initials: J
authors.lastname: Puenpa
authors.forename: Sheng-Wen
authors.initials: SW
authors.lastname: Huang
authors.forename: Ya-Fang
authors.initials: YF
authors.lastname: Wang
authors.forename: John
authors.initials: J
authors.lastname: Mauleekoonphairoj
authors.forename: Jen-Ren
authors.initials: JR
authors.lastname: Wang
authors.affiliation: Center of Excellence in Clinical Virology, Department of Pediatric, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand. yong.p@chula.ac.th.
authors.forename: Yong
authors.initials: Y
authors.lastname: Poovorawan
mesh_terms: D000293:Adolescent; D000328:Adult; D044466:Asian People; D002648:Child; D002675:Child, Preschool; D029821:Enterovirus A, Human / Q000235:genetics / Q000472:pathogenicity*; D004769:Enterovirus Infections / Q000097:blood* / Q000453:epidemiology* / Q000821:virology; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D011153:Population; D016036:Seroepidemiologic Studies; D012703:Serotyping