基于计算流行病学的埃博拉出血热的传播与爆发仿真研究

摘要

目的 本研究旨在模拟外来输人性埃博拉出血热(Ebola virus disease,EVD)病例出现后,不同的防控策略对该病在我国传播及爆发流行模式的影响,并为相关决策部门提供一种循证决策依据.方法 选用传染病SIR动力学模型建模.模拟病毒输入区域为我国南方某特大型城市群,该城市群人口5000万,所有人均为易感者.出现输入性病例,模拟情况分别包含单个感染者入境I(0)=1,某小型旅行者团体(全为感染者)入境I(0)=5及I (0)=10.I(0)我们称为“零号感染者”,其发病过程呈现典型的埃博拉出血热发病过程.其传播能力用β表示.对于输入性埃博拉感染者进入我国后,从其发病到得到控制(启动紧急预案)的时间t*设定了如下特征参数:t*=6,12,18,24,30 h.传播模式设定如下:S0=5×108,I0∈[1,20];λ∈(0.1);q∈(0.1];t*∈{6,12,18,24}h.结果 零号感染者输入后,随着应急预案启动的时刻t*变化,病毒暴发曲线为指数型,指数方程为y=1.053e1.801,模型拟合度R2 =1,RSME =0.118 5.如在给定启动应急预案的时间点后(即在同一时间点启动应急预案),零号感染者的数量与被感染者人数上限之间的关系表现为线性增加,线性方程为y=7.605x,模型拟合度R2 =1.以最好模型估计,若零号感染者人数为1,输入后在6h内即被识别并启动应急预案进行处置,则感染人数为7人;若其被隔离时间延长为12,18,24及30 h,则对应的感染人数分别为32、400、1400和8600.以最坏模型估计,若零号感染者人数为10,在6,12,18,24及30 h后才被识别并启动应急预案进行处置,则在对应的新发感染人数分别为67、380、2400、1.4万和8.7万.结论 埃博拉出血热在我国爆发流行的可能性较低,即使出现输入性病例,只要能严格执行国家卫计委的相关规定,该病的传播范围将极为有限.应该加大投入,加强对一线传染科、急诊科和发热门诊医护人员的培训,使之能及时识别该病并加以处置.%Objective This study presents a computational simulation model to determine the effect of different control strategies on the transmission and outbreak patterns of Ebola virus disease (EVD) in China,in order to provide evidence for policy makers and government authorities.Methods and Materials We selected the SIR dynamics model.We assumed that the EVD patient (s) would enter China at certain urban agglomerations of Southern China.The population in these urban agglomerations is over 50 million and all of them are susceptible to EVD.EVD patient (s) who enter certain ports of these urban agglomerations would be defined as "patient zero" and marked as 1 (0).we set up number of I (0) as:n =1,5,10.β is the transmission capacity of Ebola virus.Given t* the time from occurrence of isolation of EVD patients is t* =6,12,18,24,30 hours.Thus,we have a set of simulation parameters:S0 =5 × 108,I0∈ [1,20]; λ∈ (0,1); q∈ (0,1]; t* ∈ {6,12,18,24} h; Results When patient zero arrives,at the same time t* evolves,the EVD outbreak curve presents as an exponential pattern,the equation is y =1.053e1.801x.Let t* is fixed,then the relation between the numbers of patient zero and the peak of new infections is obeying a linear model,and the equation is y =7.605x.In the best case scenario,the number of patient zero is 1,and is isolated no more than 6 hours after the onset.Under such a circumstance,the new cases who will be infected by the patient zero would only be 7.However,if the isolation time of patient zero is postponed to 12,18,24 and 30 hours,the new cases who will be infected by the patient zero will increase to 32,400,1400 and 8600,respectively.If the number of patient zero is 10,and is isolated after 6,12,18,24 and 30 hours of the onset,then the new cases infected by patient zero would be 67,380,2400,14 000 and 87 000,respectively.Conclusion The possibility of an outbreak of EVD in China is quite low when relevant regulations made by national health authorities are well conducted.It means patient zero and the intimate contact persons should be isolated within 6 hours when patient zero symptoms and signs occur.In addition,we suggest an increased investment in capacity building and precaution equipment for health providers who work in emergency departments,departments of transmission of diseases and fever clinics in hospitals.