1 Mathematical Institute, University of Oxford , Andrew Wiles Building, Radcliffe Observatory Quarter, Woodstock Road, Oxford OX2 6GG , UK.
2 Department of Zoology, University of Oxford , South Parks Road, Oxford OX1 3PS , UK.
Philos Trans R Soc Lond B Biol Sci. 2019 Jun 24;374(1775):20180274. doi: 10.1098/rstb.2018.0274.
The high frequency of modern travel has led to concerns about a devastating pandemic since a lethal pathogen strain could spread worldwide quickly. Many historical pandemics have arisen following pathogen evolution to a more virulent form. However, some pathogen strains invoke immune responses that provide partial cross-immunity against infection with related strains. Here, we consider a mathematical model of successive outbreaks of two strains-a low virulence (LV) strain outbreak followed by a high virulence (HV) strain outbreak. Under these circumstances, we investigate the impacts of varying travel rates and cross-immunity on the probability that a major epidemic of the HV strain occurs, and the size of that outbreak. Frequent travel between subpopulations can lead to widespread immunity to the HV strain, driven by exposure to the LV strain. As a result, major epidemics of the HV strain are less likely, and can potentially be smaller, with more connected subpopulations. Cross-immunity may be a factor contributing to the absence of a global pandemic as severe as the 1918 influenza pandemic in the century since. This article is part of the theme issue 'Modelling infectious disease outbreaks in humans, animals and plants: approaches and important themes'. This issue is linked with the subsequent theme issue 'Modelling infectious disease outbreaks in humans, animals and plants: epidemic forecasting and control'.
现代高频旅行导致人们担忧一种致命病原体可能迅速在全球传播的毁灭性大流行病。许多历史大流行病都是由于病原体进化为更具毒性的形式而出现的。然而，一些病原体株会引发免疫反应，提供对相关菌株感染的部分交叉免疫。在这里，我们考虑了两种菌株（低毒力（LV）菌株爆发后紧接着是高毒力（HV）菌株爆发）连续爆发的数学模型。在这些情况下，我们研究了旅行率和交叉免疫的变化对 HV 菌株大流行发生的概率以及该爆发规模的影响。由于接触 LV 菌株，在亚种群之间频繁旅行可能会导致对 HV 菌株的广泛免疫。因此，HV 菌株的大流行不太可能发生，并且随着更多连接的亚种群，其规模可能更小。交叉免疫可能是自 1918 年流感大流行以来，一个世纪以来没有出现像 1918 年流感那样严重的全球大流行病的一个因素。本文是主题为“人类、动物和植物传染病暴发的建模：方法和重要主题”的一部分。该主题与后续的主题为“人类、动物和植物传染病暴发的建模：流行预测和控制”的主题问题相关联。
