基于离散随机动力学模型对长春市新型冠状病毒肺炎流行趋势的研究

Epidemic trend of COVID-19 transmission in Changchun based on a discrete stochastic dynamical model analysis

目的通过拟合长春市2021年1月5日—3月3日新型冠状病毒肺炎疫情流行状况,探究不同防控措施对疫情发展的影响,为后续疫情防控提供数量依据和理论支撑。方法考虑输入性病例,利用仓室建模方法建立一类具有输入性病例和阶段性防控策略的离散随机动力学模型。基于吉林省卫生健康委员会公布的2021年1月5日—3月3日的隔离潜伏者病例数、确诊者病例数、治愈者病例数,利用非线性最小二乘法拟合模型参数。利用参数敏感性分析探讨不同防控措施对由输入性病例诱导的新型冠状病毒肺炎潜在二次暴发的可能性、规模和抑制作用的影响。结果有症状感染者、无症状感染者及潜伏者传染系数估计值比值为4∶2∶1;基本再生数和最小有效再生数估计值分别为4.18与0.08;防止新型冠状病毒肺炎二次暴发的隔离率阈值估计值为0.05;当隔离率>0.3时,长春市无二次暴发风险;完全解除隔离会诱导二次暴发,若及时提高隔离率可抑制疫情发展。结论本研究建立的离散随机动力学模型拟合结果合理,每日有效再生数变化趋势显示长春市2021年1—3月疫情控制措施得当,将隔离率保持在一个较高水平,能有效控制由输入性病例诱导的局部地区疫情的二次暴发。

Objective To discuss the impact of several measures on the control of COVID-19,and to provide quantitative basis and theoretical support for subsequent epidemic prevention by fitting the epidemic trend of COVID-19in Changchun from January to March,2021through a discrete stochastic dynamical model.Methods A discrete stochastic dynamical model was established by using the compartment modeling method.Based on the number of isolated latent cases,confirmed cases and cured cases released by the Health Commission of Jilin province from January to March,2021,the nonlinear least square method was used to fit parameters of the model.Parameter sensitivity analysis was applied to assess the impact of different control measures on the possibility,final size and inhibition of a potential secondary outbreak triggered by imported cases.Results The estimated value ratio of infectious coefficient of symptomatic cases,asymptomatic cases and latent cases was 4∶2∶1.The estimated values of basic reproduction number and minimum effective reproduction number were 4.18and 0.08,respectively.The estimated threshold of isolation rate for the prevention of a secondary outbreak of COVID-19was 0.05.When an isolation rate was higher than 0.3,there was no risk of secondary outbreak in Changchun.The complete lifting of isolation could cause secondary outbreaks,and the spreading of COVID-19can be restrained if a timely increase of the isolation rate occurred.Conclusions The fitting results of the proposed discrete stochastic dynamical model are reasonable.The changing trend of daily effective reproduction number shows that the control measures are appropriate and effective in Changchun from January to March,2021,which is able to keep the isolation rate at a higher level in order to effectively control the secondary outbreaks in local areas caused by imported cases.