PDF(Pubmed)
Abstract：
The E/S (exposed/susceptible) ratio is analyzed in the SEIR model. The ratio plays a key role in understanding epidemic dynamics during the 2014-2016 Ebola outbreak in Sierra Leone and Guinea. The maximum value of the ratio occurs immediately before or after the time-dependent reproduction number (Rt) equals 1, depending on the initial susceptible population (S(0)). It is demonstrated that transmission rate curves corresponding to various incubation periods intersect at a single point referred to as the Cross Point (CP). At this point, the E/S ratio reaches an extremum, signifying a critical shift in transmission dynamics and aligning with the time when Rt approaches 1. By plotting transmission rate curves, β(t), for any two arbitrary incubation periods and tracking their intersections, we can trace CP over time. CP serves as an indicator of epidemic status, especially when Rt is close to 1. It provides a practical means of monitoring epidemics without prior knowledge of the incubation period. Through a case study, we estimate the transmission rate and reproduction number, identifying CP and Rt = 1 while examining the E/S ratio across various values of S(0).
摘要：
在SEIR模型中分析E/S(暴露/易感)比率。该比率在了解2014-2016年塞拉利昂和几内亚埃博拉疫情期间的疫情动态方面发挥着关键作用。根据初始易感群体(S(0)),该比率的最大值出现在时间相关再现数(Rt)等于1之前或之后。证明了对应于各种孵育期的传输速率曲线在称为交叉点(CP)的单个点处相交。在这一点上,E/S比达到极值，标志着变速器动力学的关键转变，并与Rt接近1的时间对齐。通过绘制传输速率曲线，β（t），对于任何两个任意的潜伏期，并跟踪它们的交叉点，随着时间的推移，我们可以追踪CP。CP是流行病状态的指标，特别是当Rt接近1时。它提供了一种在不事先了解潜伏期的情况下监测流行病的实用方法。通过一个案例研究,我们估计传播速率和复制次数，识别CP和Rt=1,同时检查S(0)的各种值的E/S比。
