title: An outbreak of influenza A(H1N1)pdm09 virus in a primary school in Vietnam.
abstract: BACKGROUND
  Despite school pupils being at greatest risk during the 2009 influenza pandemic there are limited data on outbreaks of influenza A(H1N1)pdm09 in primary schools in South-East Asia. This prospective cohort study describes an outbreak of influenza A(H1N1)pdm09 in a primary school in rural Vietnam.
  
  
  RESULTS
  In total 103 cases of influenza-like illness were found among the 407 pupils in the primary school. Ten of these were laboratory confirmed cases of influenza A(H1N1)pdm09 virus. The overall attack rate (AR) was 25% (103/407), and was highest (41%) in grade 4 pupils, where the outbreak started. All cases in the outbreak presented with a mild and self-limiting illness, acute respiratory symptoms and fever. Public health interventions to contain the outbreak could explain the lower attack rates in other grades. Ill pupils were asked to stay at home. Oseltamivir was not given to pupils and the school did not close during the outbreak. The last detected case occurred 12 days following identification of the first case.
  
  
  CONCLUSIONS
  This is the first report of an outbreak of influenza A(H1N1)pdm09 among pupils in a primary school in Vietnam. High attack rates in Grade 4 pupils suggest shared activities contributed to transmission. The public health response using non-pharmaceutical measures may have played a role in ending the outbreak.
authors.affiliation: National Institute of Hygiene and Epidemiology, Hanoi, Vietnam. trannhuduong@gmail.com.
authors.forename: Tran Nhu
authors.initials: TN
authors.lastname: Duong
authors.affiliation: National Institute of Hygiene and Epidemiology, Hanoi, Vietnam. poemhnvn@yahoo.com.
authors.forename: Nguyen Thi Thi
authors.initials: NT
authors.lastname: Tho
authors.affiliation: National Institute of Hygiene and Epidemiology, Hanoi, Vietnam. ngtrhien@yahoo.com.
authors.forename: Nguyen Tran
authors.initials: NT
authors.lastname: Hien
authors.affiliation: World Health Organization, Hanoi, Vietnam. olowokureb@who.int.
authors.forename: Babatunde
authors.initials: B
authors.lastname: Olowokure
mesh_terms: D002648:Child; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000502:physiology*; D007251:Influenza, Human / Q000453:epidemiology* / Q000473:pathology / Q000635:transmission / Q000821:virology; D008297:Male; D011446:Prospective Studies; D012307:Risk Factors; D012424:Rural Population; D012574:Schools; D012720:Severity of Illness Index; D013334:Students; D014744:Vietnam / Q000453:epidemiology