A role of high impact weather events in waterborne disease outbreaks in Canada, 1975 – 2001
Recent outbreaks of Escherichia coli O157:H7, Campylobacter , and Cryptosporidium have heightened awareness of risks associated with contaminated water supply. The objectives of this research were to describe the incidence and distribution of waterborne disease outbreaks in Canada in relation to preceding weather conditions and to test the association between high impact weather events and waterborne disease outbreaks. We examined extreme rainfall and spring snowmelt in association with 92 Canadian waterborne disease outbreaks between 1975 and 2001, using case-crossover methodology. Explanatory variables including accumulated rainfall, air temperature, and peak stream flow were used to determine the relationship between high impact weather events and the occurrence of waterborne disease outbreaks. Total maximum degree-days above 0°C and accumulated rainfall percentile were associated with outbreak risk. For each degree-day above 0°C the relative odds of an outbreak increased by a factor of 1.007 (95% confidence interval [CI] = 1.002 – 1.012). Accumulated rainfall percentile was dichotomized at the 93rd percentile. For rainfall events greater than the 93rd percentile the relative odds of an outbreak increased by a factor of 2.283 (95% [CI] = 1.216 – 4.285). These results suggest that warmer temperatures and extreme rainfall are contributing factors to waterborne disease outbreaks in Canada. This could have implications for water management and public health initiatives.
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Document Type: Research Article
Department of Mathematics and Statistics, University of Guelph, Guelph, Ontario, Canada
Foodborne, Waterborne and Zoonotic Infections Division, Centre for Infectious Disease Prevention and Control, Population and Public Health Branch, Public Health Agency of Canada, Ontario, Canada
Department of Population Medicine, University of Guelph, Guelph, Ontario, Canada
HPRP Project, University of Guelph, Ontario, Canada
Meteorological Service of Canada, Environment Canada, Toronto, Ontario, Canada
June 1, 2006
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