一起食源性伤寒、副伤寒暴发的流行病学调查

Epidemiological investigation of an outbreak of foodborne typhoid and paratyphoid

目的查明2005年宁波市发生的一起伤寒、副伤寒暴发疫情的流行因素,为预防控制提供依据。方法对病例进行流行病学个案调查,并采用配对的病例对照研究,采集市场贝壳类海产品进行实验室检测。对现场调查资料应用描述性流行病学和卫生统计学方法进行分析。结果本起疫情共发生伤寒、副伤寒1029例,发病率为13.10/10万;发病曲线呈双峰状,病例分布以市区为中心波及到周边地区,发病以25～55岁年龄的青壮年为主;流行病学1:1配对调查显示:生吃毛蚶和牡蛎者患病的危险分别为对照组的4.0倍和23.0倍(95%CI分别为1.45～11.0和5.1～103.6);同时从市场摊位所采集的牡蛎和毛蚶样品中,各检出1株甲型副伤寒沙门菌。结论此次疫情是由生吃受污染牡蛎、毛蚶等贝壳类海水产品所引起的。

Objective The study was conducted to identify the epidemiological factors causing the outbreak of typhoid and paratyphoid in Ningbo in 2005, providing evidence for the prevention and control approaches. Methods Epidemiological case studies were implemented accompanied with paired casecontrol studies. Shellfish from seafood market was collected for laboratory tests. Information on the spot was analyzed with descriptive epidemiology and health statistical methods. Results A total of 1029 cases of typhoid and paratyphoid were found in the epidemic with the incidence rate of 13.10/lakh. A bimodal-shaped curve of onsets was depicted. The cases had been distributing in the peripheral areas and centered on the urban area, 25-55-year-old age adults constituting the major involved population. The 1 ：1-paired epidemiological survey revealed a 4.0 times higher risk among the raw-cockle eaters and a 23.0 times higher risk among raw oyster eaters than the control group （95% CI：1.45-11.0 and 5.1-103.6）. Meanwhile, Salmonella paratyphi A was detected from both cockle and oyster samples from the market. Conclusion The epidemic is triggered by people eating contaminated seafood such as raw oysters, cockles and other shellfishes.