摘要
目的 了解由新冠病毒原型株和奥密克戎变异株引起的新冠肺炎疫情流行病学特征差异,总结防控经验,为云南边境地区实时调整防控措施提供参考依据。方法 对瑞丽市2021年3月29日-4月19日(以下简称新冠病毒原型株疫情)及2022年2月16日-3月26日(以下简称奥密克戎变异株疫情)两起新冠肺炎疫情的三间分布、核酸检测Ct值、潜伏期及密切接触者续发情况、聚集性疫情等方面进行对比描述性分析。结果 两起疫情均由境外输入引起,新冠病毒原型株疫情以确诊病例为主占79.49%(93/117),奥密克戎变异株疫情以无症状感染者为主,占81.77%(314/384),两起疫情感染者临床分型差异有统计学意义(χ^(2)=177.254,P <0.001);新冠病毒原型株疫情感染者确诊时核酸检测ORF1ab基因及N基因Ct值均高于奥密克戎变异株疫情,差异有统计学意义(Z=6.089,6.924,P<0.001);奥密克戎变异株疫情<15岁及≥60岁组占比较新冠病毒原型株疫情有较大幅度上升,两起疫情年龄分布差异有统计学意义(χ^(2)=33.236,P<0.001);两起疫情潜伏期M(P25,P75)分别为3(1,4.75)、3(2~5)d,差异无统计学意义(Z=–1.54,P=0.124),潜伏期<7 d分别占88.75%和95.24%;两起疫情密切接触者感染续发率为1.17%(80/6 833)、2.78%(145/5 223),其中核心密接续发率为6.3%(58/920)、6.23%(111/1 782),一般密接、次密接中均无续发病例,两起疫情均显示在共同居住生活续发率最高,其次是聚餐;新冠病毒原型株疫情共发生聚集性疫情11起,占所有感染者的76.07%,奥密克戎变异株疫情发生聚集性疫情48起,占所有感染者的33.85%。结论 奥密克戎变异株感染者无症状比例高于新冠病毒原型株感染者,但奥密克戎变异株传染性强于新冠病毒原型株。云南边境地区应加强对周边邻国新冠肺炎疫情态势研判,切实落实重点人群监测、密切接触者和次级密切接触者分类分层管理等防控措施,持续提高老年人、<15岁等适龄人群的免疫接种和序贯接种覆盖率,以实现外防输入,动态清零的防控策略。
Objective To examine the difference in epidemiological characteristics of coronavirus disease 2019(COVID-19) epidemics caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) prototype strain and Omicron variant in a border area of Yunnan province for providing references to real-time adjustment of regional measures on COVID-19 epidemic prevention and control. Methods Field surveys were conducted to collected relevant information on confirmed cases, asymptomatic infections, close contacts and secondary close contacts from two COVID-19 outbreaks in Ruili – a border city of Yunnan province: an epidemic during March 29 – April 19, 2021 caused by SARS-CoV-2 prototype strain based on whole gene sequencing(abbreviated as prototype-caused epidemic) and an another during February 16 –March 26, 2022 caused by SARS-CoV-2 Omicron variant BA.2(variant-caused epidemic). Descriptive statistics were performed to compare epidemiological characteristics between the two COVID-19 outbreaks. Results Both the two outbreaks were induced by imported cases from abroad. The majority of sufferers were confirmed cases(93/117, 79.49%) for the prototype-caused epidemic and were asymptomatic infections(314/384, 81.77%) for the variant-caused epidemic, with a significant difference in the proportion between the two epidemics(χ^(2) = 177.254, P < 0.001). In nucleic acid tests at the time of diagnosis, the cycle threshold(Ct) values of ORF1ab gene and N gene for the cases infected with SARS-CoV-2 prototype strain were significantly higher than those for the cases with SARS-CoV-2 Omicron variant infection(Z = 6.089, 6.924, P <0.001). The proportions of cases aged < 15 years and > 60 years in the variant-caused epidemic were significantly higher than those in the prototype-caused epidemic(χ^(2) = 33.236, P < 0.001). The incubation period(median [M], 25th percentile [P25],75th percentile [P75]) for the secondary infections among close contacts was not significantly different between the two epidemics(3 [1,4.75] vs. 3 [2, 5], Z = – 1.54, P = 0.124), with 88.75% and 95.24% of the secondary infections having the incubation period less than 7 days for the prototype-and variant-caused epidemic. The secondary infection rate of close contacts was 1.17%(80/6 833) and 2.78%(145/5 223) and the rate of core close contact was 6.3%(58/920) and 6.23%(111/1 782)for the prototype-and variant-caused epidemic. No secondary infection was detected among general close contacts and secondary close contacts and the secondary infection rate was the highest among the contacts living together with confirmed cases, followed by that among those having dinner with the confirmed cases. Totally 11 and 48 clustering epidemics were identified in the two COVID-19 outbreaks caused by SARS-CoV-2 prototype strain and Omicron variant, involving 76.07%and 33.85% of all diagnosed cases during the two outbreaks. Conclusion Compared to SARS-CoV-2 prototype strain,SARS-CoV-2 Omicron variant BA.2 exhibits higher infectivity and could result in more asymptomatic infections. The study results should be considered in developing measures on COVID-19 epidemic prevention and control.
作者
邱玉冰
贾曼红
陈金瓯
郑尔达
杨云斌
杨蕊
杨星
李真晖
付朝智
许琳
QIU Yu-bing;JIA Man-hong;CHENG Jin-ou(Institute of Tuberculosis Prevention and Control,Yunnan Provincial Center for Disease Control and Prevention,Kunming,Yunnan Province 650022,China)
出处
《中国公共卫生》
CAS
CSCD
北大核心
2022年第9期1175-1180,共6页
Chinese Journal of Public Health
关键词
新冠肺炎疫情
新冠病毒原型株
奥密克戎变异株
流行特征
云南省边境地区
COVID-19 epidemic
SARS-CoV-2 prototype
SARS-CoV-2 Omicron variant
prevalence characteristics
border area of Yunnan province
