Background This study examined the relationship between the bacteriological contamination of drinking water from private wells and acute gastrointestinal illness (AGII), using current government standards for safe drinking water.

      Methods
      A prospective cohort study was conducted using 235 households (647 individuals) randomly selected from four rural hamlets. Data were collected by means of a self-administered questionnaire, a self-report diary of symptoms and two drinking water samples.


      Results
      Twenty percent of households sampled, had indicator bacteria (total coliform or Escherichia coli (E. coli)) above the current Canadian and United States standards for safe drinking water. No statistically significant associations between indicator bacteria and AGII were observed. The odds ratio (OR) for individuals exposed to E. coli above the current standards was 1.52 (95% confidence interval (CI), 0.33–6.92), compared to individuals with levels below current standards. The odds ratio estimate for individuals exposed to total coliforms above the current standards was 0.39 (95% CI, 0.10–1.50).


      Conclusions
      This study observed a high prevalence of bacteriological contamination of private wells in the rural hamlets studied. Individual exposure to contaminated water defined by current standards may be associated with an increased risk of AGII.