title: Epidemiological investigation of two parallel gastroenteritis outbreaks in school settings.
abstract: BACKGROUND
  Two parallel gastroenteritis outbreaks occurred in an elementary school and a neighboring kindergarten in Kilkis, Northern Greece in 2012. The aim of the study was the investigation of these two parallel outbreaks as well as their possible source.
  
  
  METHODS
  Two retrospective cohort studies were performed to identify the mode and the vehicle of transmission as well as the possible connection between them.
  
  
  RESULTS
  Elementary school and kindergarten populations of 79.9% (119/149) and 51.1% (23/45) respectively, participated in the study. Case definition was satisfied by 65 pupils from the elementary school and 14 from the kindergarten. For elementary school, 53 cases were considered primary cases of the outbreak and were included in the analysis. Based on the results of the multivariate analysis, consumption of tap water was the only statistically significant independent risk factor of gastroenteritis (RR = 2.34, 95% C.I.: 1.55-3.53).; a finding supported by the shape of the epidemic curve which referred to a common point source outbreak with secondary cases. For kindergarten, no statistically significant risk factor was identified, and the epidemic curve supported a person-to-person transmission according univariate analysis. Norovirus GI and GII and human Adenovirus were detected by Real Time PCR in stool samples from seven children of elementary school, but stool samples were not collected by children of the kindergarten.
  
  
  CONCLUSIONS
  Even though the etiological agent of the outbreak was not verified, combined epidemiological and laboratory results were in favor of a waterborne viral gastroenteritis outbreak at the elementary school, followed by a person to person spread at the kindergarten.
authors.affiliation: Hellenic Center for Disease Control and Prevention, Athens, Greece.
authors.forename: Kassiani
authors.initials: K
authors.lastname: Mellou
authors.forename: Theologia
authors.initials: T
authors.lastname: Sideroglou
authors.forename: Maria
authors.initials: M
authors.lastname: Potamiti-Komi
authors.forename: Petros
authors.initials: P
authors.lastname: Kokkinos
authors.forename: Panos
authors.initials: P
authors.lastname: Ziros
authors.forename: Theano
authors.initials: T
authors.lastname: Georgakopoulou
authors.forename: Apostolos
authors.initials: A
authors.lastname: Vantarakis
mesh_terms: D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005260:Female; D005759:Gastroenteritis / Q000453:epidemiology*; D006115:Greece / Q000453:epidemiology; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D012574:Schools; D011795:Surveys and Questionnaires