title: Investigation of Two Outbreaks of Gastroenteritis in Tržič in September 2011.
abstract: BACKGROUND
  An outbreak of gastroenteritis of etiologically unspecified origin and an outbreak of Salmonellosis occurred simultaneously in September 2011 in Tržič. The purpose of the investigation of both outbreaks was to identify the most probable source and the mode of transmission and to implement preventive measures.
  
  
  METHODS
  In two retrospective case-control studies, the association between gastroenteritis of etiologically unspecified origin or Salmonellosis and food from a restaurant or drinking tap water were tested by univariate and multivariate analysis. The subject in the first study was a sick person with salmonellosis, and the subject in the second study was a resident that developed diarrhoea and/ or vomiting. Cases were reported by doctors, and controls were selected from healthy persons who responded to the questionnaire.
  
  
  RESULTS
  A person exposed to food from the restaurant had a 24.8 times higher odds ratio (univariate analysis OR 24.8, 95% CI 7.5 to 82.3, p <0.05; multivariate analysis OR 14.7, 95% CI 3.5 - 61.3, p <0.05) for salmonellosis than non-exposed. A resident exposed to tap water from specific water source had a 3.4 times higher odds ratio (univariate analysis of OR 3.4, 95% CI 2.2 to 5.1 is p <0.05, multivariate analysis of RO 2.9, 95% CI 1, 7 to 5.3, p <0.05), for gastroenteritis of unspecific etiology than non-exposed. The dose response relationship was also statistically significant.
  
  
  CONCLUSIONS
  Analytical cases - controls studies confirmed a causal relationship between salmonellosis and food from the specific restaurant and the causal relationship between gastroenteritis of etiologically unspecified origin and drinking tap water from specific water source. Salmonella enteritidis may have entered into the restaurant through tap water.
authors.affiliation: Health Care Centre Gorenja vas, Trata 7, 4224 Gorenja vas, Slovenia.
authors.forename: Andreja
authors.initials: A
authors.lastname: Krt Lah
authors.affiliation: National Institute of Public Health, Trubarjeva 2, 1000 Ljubljana, Slovenia.
authors.forename: Tatjana
authors.initials: T
authors.lastname: Frelih
authors.affiliation: National Laboratory for Health, Environment and Food, Prvomajska 1, 2000 Maribor, Slovenia.
authors.forename: Irena
authors.initials: I
authors.lastname: Grmek Košnik
keywords: Salmonella Enteritidis; epidemiology; gastroenteritis; outbreak