Zheng Zhibei, Sun Wanwan, Duan Qiuyao, Liu Shelan, Chen Enfu, Pan Jinren
Hangzhou Center for Disease Control and Prevention, Hangzhou, China.
Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, China.
Front Public Health. 2025 Jun 13;13:1516208. doi: 10.3389/fpubh.2025.1516208. eCollection 2025.
To evaluate the efficiency of case-finding strategy for COVID-19 outbreak control during the "dynamic zero-case policy" period in Zhejiang Province, China, in 2022.
A field epidemiological observational study was conducted to describe the proportion and time distribution of all cases identified in the event. Categorical data were expressed as counts/proportions or positive rates. The proportion of control lead-time was developed to evaluate the performance of management in various at-risk populations. Positivity rates were used to evaluate the efficiency of certain case-finding approaches. The Pearson χ test was used to compare proportions between the groups.
Close-contact tracing identified 62.3% of the total cases. Low-risk area resident screening revealed 15.2% of the cases, most of which were ascertained within the first 3 days. All cases found by second-layer contact tracing had a longer control lead-time, but transmission events were believed to occur during the transportation or quarantine period. A higher proportion of positive control lead-time was more effective in curbing SARS-CoV-2 transmission on subsequent days. The proportion of control lead-time between those with and without quarantine status was statistically different (χ = 248.5, < 0.001). Four hundred and forty-two cases (0.571%) were found out of 77,462 close contacts, while 9 cases (0.104%) were found out of 8,683 second-layer contacts (χ = 32.7, < 0.001). On average, 2.2, 7.4, and 106.5 cases were detected per million tests by low-, medium-, and high-risk area residents, respectively.
Rapid and stringent comprehensive public health and social measures can contain the spread of SARS-CoV-2 in a localized area within weeks. Close-contact tracing plays a pivotal role in COVID-19 outbreak control, but contact tracing alone is insufficient to contain the transmission. Mass screening in the early stage and outbreak site exposure person tracing also play an important role for cases finding. It is suggested that in containing severe acute infections with direct transmission route in the future, if stringent social distancing requirements have already being implemented, measures such as tracing second-layer contacts, repeated mass screening for medium-or low-risk residents during the middle and late stages of the event are not recommended.
评估2022年中国浙江省在“动态清零政策”期间新冠疫情防控中病例发现策略的效率。
开展一项现场流行病学观察性研究，以描述该事件中所有确诊病例的比例和时间分布。分类数据以计数/比例或阳性率表示。采用控制提前期比例来评估对各类风险人群的管理绩效。阳性率用于评估某些病例发现方法的效率。采用Pearson χ检验比较组间比例。
密切接触者追踪发现了62.3%的病例。低风险地区居民筛查发现了15.2%的病例，其中大部分在头3天内确诊。通过次密接触者追踪发现的所有病例的控制提前期更长，但传播事件被认为发生在转运或隔离期间。较高比例的阳性控制提前期在随后几天对遏制新冠病毒传播更有效。有隔离状态和无隔离状态者的控制提前期比例在统计学上存在差异（χ = 248.5，< 0.001）。在77462名密切接触者中发现了442例（0.571%），而在8683名次密接触者中发现了9例（0.104%）（χ = 32.7，< 0.001）。低、中、高风险地区居民每百万次检测平均分别检测到2.2例、7.4例和106.5例。
迅速且严格的综合公共卫生和社会措施可在数周内遏制新冠病毒在局部地区的传播。密切接触者追踪在新冠疫情防控中起关键作用，但仅靠接触者追踪不足以遏制传播。早期大规模筛查和疫情现场暴露人员追踪对病例发现也起重要作用。建议在未来遏制具有直接传播途径的严重急性感染时，如果已经实施了严格的社交距离要求，不建议采取追踪次密接触者、在事件中期和后期对中低风险居民进行反复大规模筛查等措施。
