The potential role of high impact weather events in waterborne disease outbreaks in Canada, 1975-2001

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. The exact role weather plays in waterborne disease outbreaks though is not well understood.

The main objectives of this research were to describe the incidence and distribution of waterborne disease outbreaks in Canada and high impact weather events occurring prior to an outbreak and to test the association between high impact weather events and waterborne disease outbreaks

We examined periods of extreme rainfall events and spring snowmelt conditions in association with 169 waterborne disease outbreaks using a case-crossover methodology. Results from regression models of rainfall, temperature, peak stream flow and other explanatory variables on the likelihood of outbreak occurrence will be presented.

Knowledge gained from this research could contribute to better-informed policy decisions to deal with current concerns of waterborne disease and to develop adaptive strategies for enhanced public health and safety under future climate change conditions. With global warming, Canada is projected to experience milder winters, longer summers, drier summers in many populated areas and more events of intense precipitation. These changes in Canada’s climate could potentially impact the incidence of waterborne disease in the future.