一起新型冠状病毒肺炎聚集性疫情流行病学调查分析

Epidemiological survey and analysis on a cluster epidemic of coronavirus disease 2019

目的分析一起新型冠状病毒肺炎(简称新冠肺炎)聚集性疫情特征,同时探讨血清特异性抗体检测对流行病学调查的意义,为新冠肺炎疫情防控策略的进一步完善提供参考。方法对某县发生的一起新冠肺炎聚集性疫情进行现场流行病学调查,将管控区内所有湖北旅居史人员划归为可疑传染源。对确诊病例的密切接触者及可疑传染源采集咽拭子及血清标本,采用RT-PCR法对咽拭子进行2019-nCoV核酸检测,采用ELISA法对血清进行2019-nCoV特异性IgM、IgG抗体检测。结果确诊病例5人核酸检测阳性,其中1例连续检测6次阴性,第7次检测阳性。5例确诊病例来自2个不同的家庭,其先发病例之间及与可疑传染源均无密切接触史。密切接触者中发现1人在整个调查期内7次核酸检测均为阴性,后经血清抗体检测IgM和IgG阳性才判定为无症状感染者,其与2个家庭的先发病例均有过密切接触。管控区内可疑传染源77例,核酸检测均为阴性,血清抗体检测发现2例IgG阳性,怀疑其可能是本次聚集性疫情的感染来源。结论新冠肺炎易形成家庭内传播,相对封闭的空间存在有利于病毒传播的可能,抗体检测作为核酸检测的补充,对于发现无症状感染者,追溯无明确暴露史确诊病例的传染来源,具有重要意义。

Objective To analyze the characteristics of a cluster epidemic of coronavirus disease 2019(COVID-19),to simultaneously explore the significance of serum specific antibody detection in the epidemiological survey of COVID-19,and to provide references for further improvement of COVID-19 prevention and control strategies.Methods A field epidemiological investigation was conducted on a cluster epidemic of COVID-19 in a county.All persons who came back from Hubei in this controlled area were classified as possible source of infection.Oropharyngeal swabs and serum samples were collected from close contacts of confirmed cases and suspicious sources of infection.Reverse transcription-polymerase chain reaction(RT-PCR)was used to detect nucleic acids from 2019 novel coronavirus(2019-nCoV)in oropharyngeal swab samples,and the enzyme linked immunosorbent assay(ELISA)was employed to detect serum specific immunoglobulin M(IgM)and immunoglobulin G(IgG)antibodies to 2019-nCoV.Results Five cases were tested positive for 2019-nCoV nucleic acids,one of which was continuously negative for the first 6 times,but positive in the seventh test.The 5 confirmed cases came from 2 different families,and there was no history of close contact between the first cases of the 2 families as well as between the first cases and the suspected source of infection.Among the close contacts,one,who had close contact with the first cases of the 2 families,was determined as asymptomatic infector whose serum IgM and IgG were positive but nucleic acid tests were negative for 7 times in the whole survey period.There were 77 cases with suspected infectious sources in the controlled area,and their nucleic acid tests were all negative,but serum IgG antibody was positive in 2 cases,which might be the infectious source of this cluster epidemic.Conclusions COVID-19 is prone to occurring intra-family transmission,and the existence of a relatively closed space is conducive to the possible transmission of 2019-nCoV.Specific antibody detection can be used as a supplement to nucleic acid test,which has great significance for detecting asymptomatic patients and tracing the infectious source of confirmed cases without a clear history of exposure.