基于年龄结构的中国大陆手足口病流行特性的分析

Age-structured model and analysis of hand foot and mouth disease in China

目的分析中国大陆手足口病动态模式的可能驱动因素,估计该病流行特性的重要参数。方法将宿主分成0-9岁（儿童组）和10-75岁（年长组）年龄组,建立分年龄结构的易感者-感染者-移出者（susceptible-infected-recovered,SIR）模型。根据我国2009-2011年手足口病发病数据,估算两个年龄组的人均接触率（β）和平均感染力（λ）,及基本再生数（R0）。对模型进行计算机模拟,分析手足口病传播系统的动态特性以及学校开学对手足口病动态模式的影响。结果我国儿童组和年长组的手足口病年平均感染力分别为0.42,0.11;年人均接触率分别是1.28×10^-6,3.31×10^-7;基本再生数为8.86。在有外部驱动力（学校开学）的情况下,手足口病的发病数会有一年一次的季节性。结论我国0-9岁儿童手足口病的平均感染力高于目前文献报道的其他儿童传染病的平均感染力;≤9岁儿童间手足口病的接触率高于≥10岁人群间的接触率;每学年的开学能导致手足口病一年一次的季节性。

Objective To analyze a possible promoting factor of the seasonality pattern of the hand foot and mouth disease（HFMD） in China's Mainland,and to estimate values of important parameters of HFMD.Methods We established an age-structured susceptible-infected-recoversed（SIR） model which divides the population into two age groups,0-9 years group（child group） and 10-75 years group（elder group）.Based on the HFMD prevalence data in China from 2009 to2011,we estimated contact rates（β） and average forces of infection（λ） of the two age groups,and the basic reproduction number R0.The model was simulated to analyze the transmission dynamics of HFMD and the effect of the beginning of school year on the transmission patterns.Results The annual average force of infection of child group and elder group was0.42 and 0.11 respectively; the average contact rate per year was 1.28 × 10^-6and 3.31 × 10^-7respectively; the basic reproduction number was 8.86.With the external driving force（the beginning of school year）,the system fluctuates and shows an annual pattern.Conclusions For children under 9 years old in China,the average force of infection of HFMD is higher than that of other childhood infectious diseases reported in the literature up to now.The average contact rate among children under 9 years old is higher than that among the population of 10 years and above.The beginning of school year can lead to the annual seasonality of HFMD.