郴州市10例新冠肺炎无症状感染者的传染性分析

目的对郴州市新型冠状病毒(简称新冠病毒)无症状感染者的传染性进行分析,为制定疫情防控策略提供依据。方法追踪观察郴州市新冠病毒无症状感染者的特征和密切接触者感染情况,采用实时定量荧光方法检测新冠病毒核酸,采用胶体金法检测血清新冠病毒抗体,并进行传染性分析。结果追踪观察10例无症状感染者,其中5例转为确诊病例,为潜伏期感染者;5例持续无症状,为隐性感染者。隐性感染者的平均年龄和潜伏期感染者差异有统计学意义(P=0.037)。从时间分布来看,疫情早期以潜伏期感染者为主,中后期则以隐性感染者为主。从暴露来源看,主要为家庭生活暴露。5例潜伏期感染者胸部CT均呈现典型的新冠肺炎影像学表现,但仅有3例表现为轻微的临床症状。共追踪到无症状感染者的密切接触者264例,其中5例潜伏期感染者的“单密”108例,经检测,新冠病毒核酸阳性4例,抗体阳性5例;5例隐性感染者的“单密”38例,经检测,新冠病毒核酸和抗体均阴性;两者“混密”118例,核酸和抗体检测阳性12例。结论新冠病毒感染者中存在无症状感染者,其中潜伏期感染者具有传染性,本研究提示隐性感染者无传染性,但有待进一步验证;建议早期同时开展核酸及CT检测,可尽早发现潜伏期无症状感染者。

Infectivity of 10 asymptomatic patients with COVID-19 infection in Chenzhou City

Objective To analyze the infectivity of asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infected patients in Chenzhou City, and to provide a basis for formulating epidemic prevention and control strategies. Methods The characteristics of asymptomatic patients infected with SARS-CoV-2 and the infection situation of their close contacts in Chenzhou City were tracked. Real-time quantitative fluorescence (RT-PCR) method was used to detectSARS-CoV-2 nucleic acid. Colloidal gold method was employed to detect SARS-COV-2 antibody in serum, and infectivity analysis was performed. Results Ten cases of asymptomatic infection were followed up, of which 5 cases were diagnosed as confirmed cases, namely, patients with pre-symptomatic infection, and 5 cases were persistently asymptomatic, namely, patients with latent infection. There was a statistically significant difference in the average age between the patients with latent infection and the patients with pre-symptomatic infection (P=0.037). Time distribution revealed that pre-symptomatic infection was the main infection in the early stage of the epidemic, while latent infection was the main infection in the middle and late stages. The sources of exposure displayed that family life exposure wasthe most common. Chest CT of the 5 patients with pre-symptomatic infection showed typical imaging findings of COVID-19, but only 3 patients presented with mild clinical symptoms. A total of 264 close contacts of the asymptomatic infected patients were tracked, including 108 contacts who had been in close contact with only one asymptomatic infected patient based on the 5 pre-symptomatic infection patients. The detection showed that 4 cases were positive for COVID-19 nucleic acid and 5 cases positive for antibody. There were 38 contacts who had been in close contact with only one asymptomatic infected patient based on the 5 latent infection patients. The detection showed that COVID-19 nucleic acid and antibody were both negative. There were 118 contacts who had been in close contact with ≥ 2 infected patients based on the pre-symptomatic and latent infection patients, and 12 contacts were positive for nucleic acid and antibody. Conclusion There are asymptomatic infections in the patients infected with SARS-CoV-2, and the pre-symptomatic infection is infectious. This study indicates that the latent infection is not infectious, but it needs to be further verified. The results suggest that nucleic acid and CT examinations should be carried out simultaneously in the early stage so as to detect asymptomatic infection as soon as possible.