2020年甘肃省兰州市某高校一起诺如病毒感染暴发疫情调查

An investigation of norovirus infection outbreak in an university in Lanzhou,Gansu,2020

目的调查2020年甘肃省兰州市某大学发生的一起诺如病毒感染疫情的流行病学特征及环境因素,为诺如病毒的防控提供依据。方法设计调查表收集病例资料及其他疫情数据,采集健康、患病学生等的肛拭子和粪便样本以及环境涂片,使用诺如病毒(GⅠ/Ⅱ)核酸检测试剂盒,应用实时荧光聚合酶链式反应技术进行检测。对于GⅡ型诺如病毒阳性的样品,扩增部分RNA依赖RNA聚合酶区和衣壳区核苷酸序列并进行分析,利用诺如病毒基因在线分型工具鉴定基因型。率的比较采用χ^(2)检验。结果此次疫情共发现459例临床病例,罹患率为3.01%。其中女性罹患率(3.75%)高于男性(2.13%),差异有统计学意义(χ^(2)=34.185,P<0.001)。A、B、C、D宿舍区学生罹患率差异有统计学意义(χ^(2)=32.314,P<0.001),D区最高(3.73%),病例占总病例数的64.05%。腹泻组和无症状组诺如病毒阳性率分别为78.52%和40.82%,差异有统计学意义(χ^(2)=6.760,P=0.009)。食堂职工与后勤职工诺如病毒阳性率差异无统计学意义(χ^(2)=0.062,P=0.803)。环境检测诺如病毒均为阴性。诺如病毒基因分型为GⅡ.P17-GⅡ.17。结论本次疫情发生在学生返校时,有可能是输入性,但不排除接触传播。

Objective To describe the epidemiological characteristics and environmental factors of a norovirus infection outbreak that occurred in an university in Lanzhou,2020,and provide evidence for the prevention and control of norovirus infection.Methods A questionnaire survey was conducted to collect the incidence data of norovirus infection in the outbreak.Rectal swab and stool samples from healthy students,sick students and others,and environmental swab smears were used for norovirus detection.Norovirus(GⅠ/GⅡ)nucleic acid detection kit was used to detect all the samples by real-time fluorescence polymerase chain reaction(RT-PCR).Partial RNA-dependent RNA polymerase and capsid nucleotides of GⅡnorovirus-positive samples were amplified and analyzed.Norovirus genotypes were identified by online genotyping tool andχ²test was used to compare the rates.Results A total of 459 norovirus infection cases occurred in this outbreak,with an attack rate of 3.01%.The attack rate in women(3.75%)was higher than that in men(2.13%),and the difference was significant(χ^(2)=34.185,P<0.001).There were significant differences in the attack rate among the students from four areas of dormitory A,B,C,and D(χ^(2)=32.314,P<0.001).The norovirus attack rate was highest in area D(3.73%),with the cases accounting for 64.05%of the total.The positive rates of norovirus in diarrhea and asymptomatic groups were 78.52%and 40.82%,respectively.The difference was significant between two groups(χ^(2)=6.760,P=0.009).There was no significant difference in positive rate of norovirus between cafeteria employee group and logistic manager group(χ^(2)=0.062,P=0.803).Environmental testing for norovirus had negative result.Genotyping indicated that norovirus identified in this outbreak belonged to GⅡ.P17-GⅡ.17.Conclusion This outbreak might be an imported one by student returning after vacation,but contact transmission could not be excluded.