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目的 对一起感染性腹泻暴发疫情的病原和危险因素进行调查分析.方法 根据病例定义进行主动搜索,利用回顾性队列研究寻找可疑餐次和可疑食物.采集病例和密切接触者粪便、肛拭子等标本进行诺如病毒核酸检测和肠道致病菌分离培养.结果 该旅行团共发现病例28例,流行曲线提示为点源暴露.共采集患者和密切接触者标本分别为12件和7件,经RT-PCR检测11名患者和2名密切接触者GⅡ组诺如病毒核酸检测阳性.对其中1份阳性标本进行测序,该病毒与2014年8月日本提交的GⅡ.17型AB983218和2014年12月中国台湾提交GⅡ.17型KJ156329毒株相似度达到98％.根据诺如病毒的潜伏期和病例的发病时间推测暴露时点为2月6日中餐和晚餐可能性大.应用回顾性队列研究结果显示2月6日晚餐中的深海鱼是危险食物(RR=6.25,95％CI:1.05～37.32).结论 该起疫情是旅行团外出引起的诺如病毒感染性腹泻的暴发,感染来源可能是在旅行期间食用了诺如病毒污染的深海鱼.“,”Objective To investigate the risk factors and pathogens of an infectious diarrhea outbreak.Methods The uniform case-definition was formulated and the cases were actively searched.A retrospective cohort study was used to search the suspicious meals and food.Stool samples and anal swab samples were collected from patients and close contacts,and nucleic acid of noroviruses was detected and intestinal pathogenic bacteria were isolated.Results Twenty-eight cases of infections were found in the tourist group.The epidemic curve suggested a point source of exposure.Twelve specimens from patients and 7 specimens from close contacts in this group were collected.Eleven samples from the patients and 2 samples from close contacts were detected positive for Group Ⅱ (G Ⅱ) noroviruses.One positive sample was sequenced,which shared 98％ similarity with a Japanese strain of GⅡ.17 (AB983218,submitted on August 2014) and a Taiwan strain of GⅡ.17 (KJ156329,submitted on December 2014).Based on the incubation period of norovirus infection and the onset time of the cases,the most possible exposure point was deduced to the lunch or dinner on February 6.The retrospective cohort study showed that deep-sea fish in dinner on February 6 was the dangerous food (RR =6.25,95％ CI 1.05 ～ 37.32).Conclusions This outbreak was caused by norovirus infection.The possible source of infection was the contaminated deep-sea fish during the trip.