BACKGROUND Climate change is increasing the number and intensity of extreme weather events in many parts of the world. Precipitation extremes have been linked to both outbreaks and sporadic cases of waterborne illness. We have previously shown a link between heavy rain and turbidity to population-level risk of sporadic cryptosporidiosis and giardiasis in a major Canadian urban population. The risk increased with 30 or more dry days in the 60 days preceding the week of extreme rain. The goal of this study was to investigate the change in cryptosporidiosis and giardiasis risk due to climate change, primarily change in extreme precipitation. METHODS Cases of cryptosporidiosis and giardiasis were extracted from a reportable disease system (1997-2009). We used distributed lag non-linear Poisson regression models and projections of the exposure-outcome relationship to estimate future illness (2020-2099). The climate projections are derived from twelve statistically downscaled regional climate models. Relative Concentration Pathway 8.5 was used to project precipitation derived from daily gridded weather observation data (~ 6 × 10 km resolution) covering the central of three adjacent watersheds serving metropolitan Vancouver for the 2020s, 2040s, 2060s and 2080s. RESULTS Precipitation is predicted to steadily increase in these watersheds during the wet season (Oct. -Mar.) and decrease in other parts of the year up through the 2080s. More weeks with extreme rain (>90th percentile) are expected. These weeks are predicted to increase the annual rates of cryptosporidiosis and giardiasis by approximately 16% by the 2080s corresponding to an increase of 55-136 additional cases per year depending upon the climate model used. The predicted increase in the number of waterborne illness cases are during the wet months. The range in future projections compared to historical monthly case counts typically differed by 10-20% across climate models but the direction of change was consistent for all models. DISCUSSION If new water filtration measures had not been implemented in our study area in 2010-2015, the risk of cryptosporidiosis and giardiasis would have been expected to increase with climate change, particularly precipitation changes. In addition to the predicted increase in the frequency and intensity of extreme precipitation events, the frequency and length of wet and dry spells could also affect the risk of waterborne diseases as we observed in the historical period. These findings add to the growing evidence regarding the need to prepare water systems to manage and become resilient to climate change-related health risks.

中文翻译：

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在加拿大不列颠哥伦比亚省温哥华，由于气候变化及其对水传播疾病的影响，预计会有局部降雨事件。

背景技术气候变化正在增加世界许多地区的极端天气事件的数量和强度。极端降雨与水传播疾病的暴发和零星病例有关。先前我们已经表明，加拿大主要城市人口的大雨和浑浊与人群水平的散发性隐孢子虫病和贾第鞭毛虫病风险之间存在联系。在极端降雨一周之前的60天内，如果干燥天数达到30天或更长时间，则风险增加。这项研究的目的是调查气候变化引起的隐孢子虫病和贾第鞭毛虫病风险的变化，主要是极端降水的变化。方法隐孢子虫病和贾第鞭毛虫病病例摘自可报告的疾病系统（1997-2009年）。我们使用了分布滞后非线性Poisson回归模型和暴露-结果关系的预测来估计未来的疾病（2020-2099）。气候预测是从十二个按统计数字缩减规模的区域气候模型得出的。相对浓度路径8.5用于根据每日网格天气观测数据（约6×10 km分辨率）投影降水，这些数据覆盖了2020年代，2040年代，2060年代和2080年代服务于大温哥华地区的三个相邻流域的中心。结果据预测，在雨季（10月至3月），这些流域的降水量将稳定增加，直到2080年代，其他年份的降水量将减少。预计会有更多星期出现强降雨（> 90％）。预计到2080年代，这几周将使隐孢子虫病和贾第鞭毛虫病的年增长率增加约16％，这取决于使用的气候模型，每年相应增加55-136例。预计水传播疾病病例的增加是在潮湿月份。在每个气候模型中，与历史每月病例数相比，未来预测的范围通常相差10-20％，但所有模型的变化方向都是一致的。讨论如果我们的研究区域在2010-2015年未采取新的滤水措施，则预计隐孢子虫病和贾第鞭毛虫病的风险会随着气候变化（尤其是降水变化）而增加。除了预计的极端降水事件的频率和强度增加之外，正如我们在历史时期所观察到的那样，干湿法的频率和长度也可能影响水传播疾病的风险。这些发现增加了越来越多的证据，表明需要准备供水系统以应对和应对与气候变化有关的健康风险。