Child Health Evaluative Sciences, The Research Institute of the Hospital for Sick Children, Toronto, ON, Canada.
Ecohealth. 2009 Jun;6(2):192-9. doi: 10.1007/s10393-009-0247-8. Epub 2010 Feb 12.
Norovirus is a common cause of gastroenteritis, and is thought to be the causative agent in 68-90% of all gastroenteritis outbreaks. The seasonality of disease occurrence is sufficiently stereotyped to result in this disease being dubbed "winter vomiting disease." The genesis of this seasonality has been obscure. We sought to identify environmental factors associated with Norovirus outbreaks in Toronto, Canada. We evaluated 253 outbreaks of gastroenteritis linked to Norovirus between November 2005 and March 2008. Poisson regression models were constructed to evaluate associations between average environmental exposures and case counts. A case-crossover approach was used to evaluate associations between acute changes in environment and outbreak risk. Case-crossover analysis indicated an association between low Lake Ontario temperature (<or=4 degrees C) (hazard ratio [HR], 5.61 [95% CI, 2.81-11.12]) and high flow (>2.5 m(3)/s) in the Don River (HR, 3.17 [95% CI, 2.30-4.36]), 1-7 days prior to case occurrence. For both exposure variables, the highest hazard ratios were found 24-48 h prior to case onset. Regression models provided further support for these patterns. The association between local watershed conditions and Norovirus outbreak risk suggest a source-water reservoir for this pathogen. We hypothesize that the reservoir may be maintained through the discharge of wastewater containing virus particles; wintertime seasonality may be explained by enhanced viral persistence at low temperatures.
诺如病毒是一种常见的肠胃炎病原体，被认为是导致 68-90%的肠胃炎爆发的原因。这种疾病的季节性发生非常典型，因此被称为“冬季呕吐病”。这种季节性的起源一直不清楚。我们试图确定与加拿大多伦多诺如病毒爆发相关的环境因素。我们评估了 2005 年 11 月至 2008 年 3 月期间与诺如病毒相关的 253 次肠胃炎爆发。构建了泊松回归模型，以评估平均环境暴露与病例数之间的关联。采用病例交叉方法评估环境急性变化与爆发风险之间的关联。病例交叉分析表明，安大略湖湖水温度低（<=4°C）（危险比 [HR]，5.61 [95%CI，2.81-11.12]）与唐河高流量（>2.5 m³/s）（HR，3.17 [95%CI，2.30-4.36]）与病例发生前 1-7 天有关。对于这两个暴露变量，在病例发生前 24-48 小时发现最高的危险比。回归模型进一步支持了这些模式。当地集水区条件与诺如病毒爆发风险之间的关联表明，该病原体存在水源水库。我们假设该水库可能通过排放含有病毒颗粒的废水来维持，冬季的季节性可能是由于低温下病毒的持续时间延长所致。
