Epidemiology and Infection

  • Epidemiology and Infection / Volume 144 / Issue 07 / May 2016, pp 1371-1385
  • Copyright © Cambridge University Press 2015 This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.
  • DOI: http://dx.doi.org/10.1017/S0950268815002083 (About DOI), Published online: 13 November 2015

Original Papers

Gastrointestinal infection

Estimating the number of cases of acute gastrointestinal illness (AGI) associated with Canadian municipal drinking water systems

H. M. MURPHYa1, M. K. THOMASa1, D. T. MEDEIROSa2, S. McFADYENa2 and K. D. M. PINTARa1 c1

a1 Centre for Food-borne, Environmental and Zoonotic Infectious Diseases, Public Health Agency of Canada, Guelph, ON, Canada

a2 Water and Air Quality Bureau, Healthy Environments and Consumer Safety Branch Health Canada, Ottawa, ON, Canada


The estimated burden of endemic acute gastrointestinal illness (AGI) annually in Canada is 20·5 million cases. Approximately 4 million of these cases are domestically acquired and foodborne, yet the proportion of waterborne cases is unknown. A number of randomized controlled trials have been completed to estimate the influence of tap water from municipal drinking water plants on the burden of AGI. In Canada, 83% of the population (28 521 761 people) consumes tap water from municipal drinking water plants serving >1000 people. The drinking water-related AGI burden associated with the consumption of water from these systems in Canada is unknown. The objective of this research was to estimate the number of AGI cases attributable to consumption of drinking water from large municipal water supplies in Canada, using data from four household drinking water intervention trials. Canadian municipal water treatment systems were ranked into four categories based on source water type and quality, population size served, and treatment capability and barriers. The water treatment plants studied in the four household drinking water intervention trials were also ranked according to the aforementioned criteria, and the Canadian treatment plants were then scored against these criteria to develop four AGI risk groups. The proportion of illnesses attributed to distribution system events vs. source water quality/treatment failures was also estimated, to inform the focus of future intervention efforts. It is estimated that 334 966 cases (90% probability interval 183 006-501 026) of AGI per year are associated with the consumption of tap water from municipal systems that serve >1000 people in Canada. This study provides a framework for estimating the burden of waterborne illness at a national level and identifying existing knowledge gaps for future research and surveillance efforts, in Canada and abroad.

(Received April 07 2015)

(Revised July 17 2015)

(Accepted August 21 2015)

(Online publication November 13 2015)

Key words

  • Epidemiology;
  • estimating disease prevalence;
  • public health;
  • water (quality)


c1 Author for correspondence: Dr K. D. M. Pintar, Centre for Food-borne, Environmental and Zoonotic Infectious Diseases, Public Health Agency of Canada, 130 Colonnade Rd, Ottawa, ON K1A 0K9, Canada. (Email: Katarina.Pintar@phac-aspc.gc.ca)