Drinking water quality and health-care utilization for gastrointestinal illness in greater Vancouver.

The risk of microbial disease associated with drinking water is presently a priority concern among North American water jurisdictions. Numerous past outbreaks, together with recent studies suggesting that drinking water may be a substantial contributor to endemic (non-outbreak related) gastroenteritis, demonstrate the vulnerability of many North American cities to waterborne diseases and have fuelled ongoing debates in Canada and the United States concerning the need for stricter water quality guidelines, changes in watershed management policies, and the need for additional water treatment. The Greater Vancouver Regional District (GVRD) water supply system serves approximately two million consumers from a system consisting of three unfiltered surface water supplies (Figure 1). Although GVRD policies reduce the potential for fecal contamination of the source water supplies by humans and domestic animals, the GVRD watersheds support many wildlife species that can potentially shed organisms pathogenic to humans. Because GVRD's water treatment strategy relies principally on watershed protection and chlorination*, and these two strategies together do not eliminate all risk of waterborne disease transmission, it is possible that some disease-causing organisms reach the consumer.