EXTREME WEATHER AND WATERBORNE DISEASE OUTBREAKS IN CANADA, 1974–2000

Recent large outbreaks of E.coli O157:H7, Campylobacter and Cryptosporidium from contaminated public water supplies in Canada have provoked considerable concern about the safety of the water supply. Many complex eco-social interactions lead to waterborne disease outbreaks; however in several Canadian cases there is evidence that weather has been influential. We investigated the potential link between extreme weather events and recorded outbreaks of disease linked to water supply systems in Canada between 1974 and 2000. A case-crossover design was used to quantify the association between he occurrence of an extreme weather event (including heavy rain, sudden thaw, drought) prior to the beginning of an outbreak of waterborne illness. Water source, type of water supply, geographical and geological factors, season and demographics were factors in the analysis. The results of the analysis shed light on vulnerabilities in Canada to impacts of extreme weather on the water supply, and have implications for adaptation to changes in past climate regimes.