Delta毒株疫情防控措施的效果评估——以南京市与扬州市为例
Evaluation of Control Measures for the Delta Variant Epidemic—A Case Study of Nanjing and Yangzhou

2019年末，新型冠状病毒首次被发现，随后疫情迅速蔓延至全球多国，对公共卫生体系及经济社会发展带来严峻挑战。随着疫情的持续发展，新冠病毒出现了多种变异株，Delta毒株因其传播速度快、感染力强以及对防控措施提出更大挑战而备受关注。面对这些挑战，我国政府不断调整防控策略，通过密切接触者追踪、隔离、控制社交距离等措施积极应对疾病扩散。本文旨在评估2021年江苏省南京市和扬州市Delta变异株新冠疫情的防控效果，为此构建了一种包含时变参数的离散随机模型，深入分析不同防控措施对疫情传播动态的影响。本文通过粒子迭代滤波算法对模型参数进行极大似然估计，较好地拟合了实际疫情数据。研究发现，Delta毒株在传播初期具有极强的传染性，南京市和扬州市的初始再生数分别为5.19和9.98，但在政府迅速采取的防控措施下，有效再生数在数日内降至1以下。通过对不同干预措施的模拟分析，结果表明隔离率、口罩佩戴率和社交距离控制对疫情传播具有显著影响，尤其是南京市精准快速的隔离策略显著减少了疫情规模。本研究为疫情防控措施的科学评估提供了重要的数学建模方法与实证依据，为未来新型传染病的防控政策制定提供了有力支持。
At the end of 2019, a novel coronavirus was first identified. The outbreak subsequently spread rapidly to countries worldwide, posing severe challenges to public health systems and socio-economic development. As the pandemic progressed, multiple variants of the virus emerged, among which the Delta variant attracted significant attention due to their high transmissibility, strong infectivity, and the greater challenges they posed to control measures. In response to these challenges, the Chinese government continuously adjusted its containment strategies, including contact tracing, isolation, and social distancing, to actively curb the spread of the disease. This study aims to evaluate the effectiveness of COVID-19 control measures during the 2021 Delta variant outbreaks in Nanjing and Yangzhou, Jiangsu Province. A discrete stochastic model with time-varying parameters was constructed to analyze the impact of various control measures on the dynamics of the epidemic. Using particle iterated filtering algorithms, the model parameters were estimated through maximum likelihood estimation, achieving a good fit to the actual epidemic data. The study found that the Delta variant exhibited extremely high transmissibility in its early stages, with initial reproduction numbers of 5.19 in Nanjing and 9.98 in Yangzhou. However, due to the rapid implementation of control measures by the government, the effective reproduction number dropped below 1 within days. Simulations of different intervention scenarios demonstrated that isolation rates, mask-wearing rates, and social distancing control significantly influenced the epidemic’s spread. Notably, Nanjing’s precise and rapid isolation strategies greatly reduced the scale of the outbreak. This research provides a robust mathematical modeling framework and empirical evidence for the scientific evaluation of control measures, offering valuable insights for future infectious disease policy-making.