重大突发公共卫生事件中的方舱医院建设情景重建研究

Scenario reconstruction of fangcang hospitals in major public health emergency

方舱医院建设是应对各类重大突发公共卫生事件的一项重要举措。现有研究大多从医学或政府管理视角定性地探讨方舱医院发挥的重要作用,还鲜有从情景重建视角研究方舱医院床位扩容的最优时空分布。本文首先构建针对重大突发公共卫生事件演化的SEIHRD模型,继而将方舱医院床位扩容问题构建为有限应急资源分配组合优化模型并设计免疫优化算法进行求解。测试结果显示,本文所给出的方舱医院床位扩容时空分布优化方案,能够对重大突发公共卫生事件中的方舱医院建设情景进行有效重建。方舱医院床位数量及其时间节点设置对累计感染者人数具有显著影响,这表明在疫情暴发初期尽早设立方舱医院,能够有效提升收治率、减少总感染人数。同时也要注意,应急救援资金投入存在阈值效应,需要设计合理的方舱医院床位扩容方案以避免应急预算资源的过度浪费。

The construction of fangcang hospitals is an important measure for people to respond to various major public health emergencies.Most of the existing studies discuss the important role of fangcang hospitals in epidemic prevention and control from the perspective of medicine or government management,while few of them focus on the time-space distribution of the bed capacity in fangcang hospitals from the perspective of scenario reconstruction.In fact,when the epidemic suddenly broke out,the existing number of beds in local hospitals could not meet the surging demand of patients.The construction of fangcang hospitals can realize the rapid expansion of bed capacity,and thus providing realistic conditions for controlling the source of infection and cutting off the transmission chain.However,to what extent did the time-space expansion of the bed capacity in fangcang hospitals affect the evolution trend of the epidemic?How to depict the interaction coupling mechanism between them?What enlightenments can we extract for the prevention and control of other unexpected epidemic outbreaks in the future?To answer these problems,we first construct a SEIHRD model for the evolution of major public health emergencies.Then,the allocation of fangcang hospital bed capacity is formulated as a combinatorial optimization model,and an immune optimization algorithm is designed to solve it.This enables the reconstruction of the scenario of constructing fangcang hospitals in major public health emergencies.The detail of the modelling formulation is as follows:First,SEIHRD infectious disease dynamics model is proposed to depict the evolution of major public health emergencies based on the theory of system dynamics.In this model,each compartment corresponds to the health status of different groups,including the susceptible(S),exposed(E),mildly infected(I1),severely infected(I2),mild infections that hospitalized(H),recovered(R)and dead(D).Note that patients in this study are divided into mild and severe infections compartments according to their symptoms,while fangcang hospitals are mainly used to receive and treat the mild infections.The number of beds in the fangcang hospitals that can be used to receive the mild infections is dynamic in this study,which depends on the resources that decision makers have and how they allocate them.This is different from the existing epidemic dynamics models,where most of the relevant parameters are fixed.Second,a general emergency decision-making framework for the expansion of bed capacity in fangcang hospitals when response to an unexpected epidemic outbreak is proposed based on the operational research optimization theory.The total number of infected individuals is taken as the optimization objective function,and the infectious disease dynamics constraints and the bed resource constraints in the fangcang hospitals are integrated.Herein,the total bed capacity of the fangcang hospitals is obtained from the capacity combination of different types of fangcang hospitals.Third,the proposed model in this paper is a mixed integer nonlinear programming model.It is difficult to obtain the accurate optimal solution.In the other side,taking a lot of time to search the optimal solution is not the best choice when emergency response to an unexpected epidemic outbreak in practice.Therefore,an improved immune optimization algorithm is adopted to solve the model.In order to verify the consistency between the results of the algorithm and the results of the model,the results of the immune optimization algorithm and the lower bound solution of the original problem model after linear relaxation are compared.Finally,the optimal time-space distribution scheme for the expansion of bed capacity in the fangcang hospitals is proposed.The result shows that the capacity of fangcang hospitals and its setting time node have a significant impact on the cumulative number of patients.Setting fangcang hospitals as soon as possible in the early stage of the outbreak can effectively improve the admission rate and reduce the number of infections.Meanwhile,it should also be noted that there is a diminishing effect of marginal utility in the emergency budget investment.It is necessary to design a reasonable capacity of fangcang hospitals to avoid waste of emergency budget.In summary,a general decision-making reference framework for emergency resource allocation is proposed in this study,by through the scenario reconstruction of fangcang hospitals in major public health emergencies.In the future,after integrating the diffusion dynamics model of other major outbreaks(such as Ebola,MERS,etc.),it can provide effective decision-making support for the construction of fangcang hospitals or emergency treatment centers in the epidemic affected areas.