西安市新型冠状病毒肺炎聚集性疫情特征

Characteristics of clusters epidemic of COVID-19 in Xi′an

目的分析西安市新型冠状病毒肺炎(Corona Virus Disease 2019,COVID-19)聚集性疫情发病特征,探讨其传播模式和传播指标,为改进防控措施提供参考依据。方法收集整理西安市全部COVID-19聚集性疫情资料,分析不同类型聚集性疫情的发病特点,并估算其潜伏期和代际间距。结果截至2020年9月6日,西安市共报告COVID-19聚集性疫情28起,涉及病例115例(确诊92例,无症状感染23例),占全市病例总数的79.31%(115/145),重症率12.17%(14/115),病死率2.61%(3/115);罹患率范围2.88%~80.00%,中位9.93%;聚集规模2~16例,中位3例。单纯家庭聚集性疫情占57.14%(16/28),续发率范围1.47%~75.00%,中位14.29%。湖北输入疫情占67.86%(19/28)。30~<70岁病例占74.78%(86/115)。病例潜伏期5.35 d(3.29,9.30),代际间距5.04 d(2.83,10.79),存在潜伏期内传染和无症状感染情况。结论西安市COVID-19疫情以家庭聚集为主要传播模式,病例潜伏期短、传染性强,及早发现并集中医学观察其全部密切接触者是防控关键。

Objective To analyze the epidemic characteristics of Corona Virus Disease 2019(COVID-19)clusters epidemics in Xi′an,explore its transmission mode and transmission indexes,and to provide references for improving prevention and control measures.Methods All the data of COVID-19 clustering epidemic cases from field epidemiological investigation reports across Xi’an were collected and sorted out,the characteristics of different types of clustering epidemic were analyzed,and corresponding latent period and intergenerational interval were estimated.Results As of September 6,2020,a total of 28 COVID-19 clusters epidemics were reported in Xi′an,involving 115 cases(92 confirmed cases and 23 asymptomatic cases),accounting for 79.31%of all(115/145)cases in the city with severe case rate of 12.17%(14/115)and a case fatality rate of 2.61%(3/115);the attack rate of clusters epidemics ranged from 2.88%to 80.00%,with a median of 9.93%,and the number of clusters epidemic cases ranged from 2 to 16 with the median of 3 cases.Simple household exposure clusters accounted for 57.14%(16/28),and the secondary incidence rate ranged from 1.47%to 75.00%with the median of 14.29%.The imported clusters epidemics from Hubei accounted for 67.86%(19/28).Cases aged 30 to<70 years accounted for 74.78%(86/115).The latent period was 5.35 d(3.29,9.30),the intergenerational interval was 5.04 d(2.83,10.79),respectively,and there were clusters epidemics caused by exposures to the cases within latent period and asymptomatic cases.Conclusion COVID-19 epidemics in Xi’an is mainly spread in family clusters and characterized with short latent period and strong infectivity,and early detection and concentrated medical observation on all close contacts are critical to the prevention and control of epidemics.