辽宁省新型冠状病毒肺炎无症状感染者流行特征分析

Epidemiological charateristics of asymptomatic COVID-19 in Liaoning province

目的分析辽宁省2020年3月11日—2021年7月31日新型冠状病毒肺炎无症状感染者流行病学特征,为制定防控策略提供参考依据。方法收集无症状感染者的流行病学调查报告、密切接触者数据库等资料,对境外输入和本土无症状感染者时间、地区、人群及时间间隔等进行描述性分析。结果共搜索到符合病例定义的无症状感染者217例,境外输入感染者多于本土感染者。境外输入无症状感染者以船员和学生为主,有13例(11.50%)转为确诊病例;从首次核酸检测阳性至解除隔离时间间隔为7~65 d,中位数为16 d;从诊断为无症状感染者到转为确诊病例的时间间隔为2~21 d,中位数为7 d。本土无症状感染者以工人和家务及待业为主;通过密接筛查发现最多,有72例(69.23%)。从末次暴露至首次核酸检测阳性时间间隔为0~21 d,中位数为4 d;无症状感染者转确诊病例从首次核酸检测阳性时间至出院时间间隔为11~44 d,中位数为21 d;始终为无症状感染者从首次核酸检测阳性时间至解除隔离时间间隔为11~37 d,中位数为17 d。潜伏期无症状感染者与隐性感染者年龄和职业构成不同。结论辽宁省境外输入无症状感染者所占比例大,本土无症状感染者主要来自于辽宁省内报告的4起聚集性疫情,发现途径在管控范围内,不会进一步在社会层面造成疫情的传播和扩散,目前防疫措施暂时无需改变。

Objective To analyze the epidemiological characteristics of asymptomatic COVID-19 in Liaoning province from March 11,2020 to July 31,2021,and to provide reference for disease prevention and control.Methods Epidemiological investigation reports and data of close contacts of asymptomatic infected persons were collected,and a descriptive analysis was performed on the infection time,region,population and time interval of asymptomatic COVID-19 cases both imported from abroad and in local areas.Results A total of 217 asymptomatic cases meeting the case definition were found,with more imported cases than domestic ones.The majority of asymptomatic imported cases were seafarers and students,and 13 cases(11.50%)became confirmed cases.The interval from the first positive nucleic acid test to the release of isolation was 7-65 days,with a median of 16 days.The time interval between diagnosis of asymptomatic infection and diagnosis of confirmed case was 2-21 days,with a median of 7 days.Majority of domestic asymptomatic infected cases were workers,housekeepers and unemployed.Most asymptomatic cases(72 cases,69.23%)were found through close contact screening.The interval from the last exposure to the first positive nucleic acid test was 0-21 days,with a median of 4 days.The interval from the first positive nucleic acid test to hospital discharge was 11-44 days among those confirmed cases from asymptomatic infection,with a median of 21 days.For asymptomatic infected persons,the interval from the first positive nucleic acid test to the lifting of isolation was 11-37 days,with a median of 17 days.The age and occupational composition of latent asymptomatic infected person and subclinically infected person were different.Conclusions Majority of asymptomatic infected cases are imported from abroad,and local asymptomatic cases are mainly from the four clusters reported in Liaoning province.It is critical to screen for asymptomatic COVID-19 infection in order to stop the spreading of the virus.For now,there is no need to change quarantine strategies.