一起诺如病毒致胃肠炎暴发疫情调查

An outbreak of Norovirus gastroenteritis in a primary school

目的调查一起胃肠炎暴发疫情,以查找病原和传播危险因素,为采取针对性防控措施扑灭疫情提供依据。方法制定病例定义,并进行流行病学调查。采集病例、桶装水及环境有关标本,进行可疑病原体PCR核酸检测。选择部分确诊病例开展诺如病毒GⅡ型排毒期调查。结果在学校共发现269例病例,学生264例(罹患率17.38%),教师5例(罹患率4.39%);学生家长中共发现7例病例;病例班级的空间分布存在显著差异,1号教学楼西面楼梯两侧班级罹患率明显高于其他班级(χ2=195.00,P<0.01)。24名学生、3名家长、1名生活老师和1名清洁工诺如病毒GⅡ型阳性,学校食堂工作人员、物体表面涂抹标本、桶装水均阴性。诺如病毒GⅡ型排毒期最短为发病后3d,最长14d,中位时间为7d。结论本次疫情为一起诺如病毒GⅡ型引起的胃肠炎暴发疫情;可能的感染来源为首例病例呕吐物污染环境后造成一次局部范围的共同暴露,通过接触传播使疫情进一步扩散。

Objective To investigate an outbreak of gastroenteritis and to identify pathogen, the source and the risk factors of infection in order to provide basis of adopting control measures. Methods A case definition and an epidemiological survey were carried out. Case specimens, bottled water and environmental relevant samples were collected for PCR test on suspected pathogens. A part of confirmed cases were selected for the investigation of Norovirus type G II during the communicable peri od. Results A total of 269 cases were found. Of which, 264 were students （attack rate： 17.38%）, 5 cases were teachers （at tack rate： 4.39%） ,7 cases were students＇ parents. An obvious difference was shown in space distribution among being at tacked classes. The attack rate of classes located in west wing of first teaching building was higher than that of other classes （X2=195.00,P〈0.01）. The test results oF 24 students, 3 parents, 1 life managing teacher and 1 cleaner were Norovirus type G II , and that of school cafeteria staffs, the surface smear samples, bottled water were negative. The communicable period of Norovirus type G II was 314 days after onset, and the median time was 7 days. Conclusion The pathogen of the outbreak of gastroenteritis was Norovirus type G II. The vomitus of the index case contaminated environment, aerosol and direct contact could be the main transmission mode.