Somura Yoshiko, Kimoto Kana, Oda Mayuko, Okutsu Yuta, Kato Rei, Suzuki Yasunori, Siki Dai, Hirai Akihiko, Akiba Tetsuya, Shinkai Takayuki, Sadamasu Kenji
Tokyo Metropolitan Institute of Public Health.
Tokyo Metropolitan Wholesale Market Sanitation Inspection Station.
Shokuhin Eiseigaku Zasshi. 2017;58(6):260-267. doi: 10.3358/shokueishi.58.260.
In February 2017, four food poisoning outbreaks occurred in Tokyo, involving ten schools. Shredded dried laver seaweed processed by a single food manufacturer in December 2016 was provided in common for the school meals that caused all four outbreaks. Of 4,209 persons exposed, 1,193 (28.3%) had symptoms of gastroenteritis. Norovirus (NoV) GII was detected in 207 (78.1%) of 265 cases by real-time RT-PCR. Thirty-one shredded dried laver seaweed samples were examined and seven (22.6%) of them were positive for NoV GII. PCR fragments of NoV ORF1/2 junction region (302 bp) from seven shredded dried laver seaweed samples and 20 clinical samples derived from the four outbreaks were sequenced. All of them displayed complete homology, and the genotype was classified as GII.17. A nearly full-length sequence (7,420 bp) of NoV RNA derived from a case was obtained by next-generation sequencer analysis and phylogenetic analysis indicated that this strain belongs to the same cluster as Hu/GII/JP/2015/GII.P17_GII.17/Kawasaki308. Thus, our investigation elucidated that the causative agent of these four serial food poisoning outbreaks was NoV GII.17 and the infectious source was a single batch of shredded dried laver seaweed. The water activity of the shredded dried laver seaweed was found to be 0.119 to 0.129. It was epidemiologically clarified that NoV does not lose infectivity for about two months even in the dry state. We conclude that a large diffuse outbreak of food poisoning caused by NoV GII.17 contamination of shredded dried laver seaweed had occurred in Tokyo. Our elucidation of the causative agent indicated that the food poisoning outbreaks in multiple areas of Japan, including Tokyo, during January to February 2017 were caused by the same contaminated food.
2017年2月，东京发生了4起食物中毒事件，涉及10所学校。2016年12月由同一家食品制造商加工的干紫菜丝被用于所有这4起事件的学校餐食中。在4209名暴露者中，1193人（28.3%）出现了肠胃炎症状。通过实时逆转录聚合酶链反应（RT-PCR）在265例病例中的207例（78.1%）检测到诺如病毒（NoV）GII型。对31份干紫菜丝样本进行了检测，其中7份（22.6%）NoV GII型呈阳性。对来自7份干紫菜丝样本和4起事件中的20份临床样本的NoV ORF1/2连接区（302 bp）的PCR片段进行了测序。所有这些片段显示出完全同源性，基因型被分类为GII.17。通过下一代测序仪分析获得了1例病例的NoV RNA的近乎全长序列（7420 bp），系统发育分析表明该毒株与Hu/GII/JP/2015/GII.P17_GII.17/Kawasaki308属于同一簇。因此，我们的调查表明这4起连续食物中毒事件的病原体是NoV GII.17，传染源是一批干紫菜丝。发现干紫菜丝的水分活度为0.119至0.129。从流行病学角度明确，即使在干燥状态下，NoV在约两个月内也不会失去传染性。我们得出结论，东京发生了由NoV GII.17污染干紫菜丝引起的大规模弥漫性食物中毒事件。我们对病原体的阐明表明，2017年1月至2月期间包括东京在内的日本多个地区的食物中毒事件是由同一受污染食品引起的。
