Two outbreaks of norovirus and acute gastroenteritis took place in Canada between November 2016 and April 2017. Both outbreaks were linked to oysters from British Columbia (BC) coastal waters. This paper describes the multi-agency investigations to identify the source and control the outbreak. Public health officials conducted interviews to determine case exposures. Traceback was conducted by collecting oyster tags from restaurants and analyzing them to determine the most common farms. Oyster samples were collected from case homes, restaurants, and harvest sites and tested for the presence of norovirus. Potential environmental pollution sources were investigated to identify the source of the outbreak. Four hundred and 49 cases were identified as part of the two outbreak waves. The oysters were traced to various geographically dispersed farms in BC coastal waters. Twelve farms were closed as a result of the investigations. No environmental pollution sources could be identified as the cause of the outbreak. Similarities in the timeframe, genotype, and geographic distribution of identified oyster farms indicate that they may have been one continuous event. Genotype data indicate that human sewage contamination was the likely cause of the outbreak, although no pollution source was identified.

中文翻译：

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2016-2017年与不列颠哥伦比亚省牡蛎有关的诺如病毒和急性胃肠炎暴发。

在2016年11月至2017年4月之间，加拿大发生了两次诺如病毒和急性肠胃炎暴发。这两次暴发均与不列颠哥伦比亚省沿海水域的牡蛎有关。本文介绍了多机构调查，以识别来源并控制爆发。公共卫生官员进行了采访以确定病例暴露。追溯是通过从饭店收集牡蛎标签并对其进行分析以确定最常见的农场来进行的。从病房，餐馆和收割场采集牡蛎样品，并测试是否存在诺如病毒。调查了潜在的环境污染源，以确定爆发的来源。在这两次爆发浪潮中，共鉴定出490例病例。牡蛎被追溯到不列颠哥伦比亚省沿海水域的各种地理分布的农场。调查结果关闭了十二个农场。没有环境污染源可以被确定为爆发原因。在确定的牡蛎养殖场的时间范围，基因型和地理分布上的相似性表明，它们可能是一个连续的事件。基因型数据表明，尽管未发现污染源，但人类污水污染可能是爆发的原因。