Griette Quentin, Raoul Gaël, Gandon Sylvain
Département de Mathématiques, Faculté des Sciences, Université de Montpellier, Place Eugène Bataillon, Montpellier, France.
CEFE - UMR 5175, campus CNRS, 1919 route de Mende, 34293 Montpellier, France.
Evolution. 2015 Nov;69(11):2810-9. doi: 10.1111/evo.12781. Epub 2015 Oct 15.
Understanding and predicting the spatial spread of emerging pathogens is a major challenge for the public health management of infectious diseases. Theoretical epidemiology shows that the speed of an epidemic is governed by the life-history characteristics of the pathogen and its ability to disperse. Rapid evolution of these traits during the invasion may thus affect the speed of epidemics. Here we study the influence of virulence evolution on the spatial spread of an epidemic. At the edge of the invasion front, we show that more virulent and transmissible genotypes are expected to win the competition with other pathogens. Behind the front line, however, more prudent exploitation strategies outcompete virulent pathogens. Crucially, even when the presence of the virulent mutant is limited to the edge of the front, the invasion speed can be dramatically altered by pathogen evolution. We support our analysis with individual-based simulations and we discuss the additional effects of demographic stochasticity taking place at the front line on virulence evolution. We confirm that an increase of virulence can occur at the front, but only if the carrying capacity of the invading pathogen is large enough. These results are discussed in the light of recent empirical studies examining virulence evolution at the edge of spreading epidemics.
了解和预测新出现病原体的空间传播是传染病公共卫生管理面临的一项重大挑战。理论流行病学表明，疫情的传播速度受病原体的生活史特征及其传播能力的制约。因此，在入侵过程中这些特征的快速演变可能会影响疫情的传播速度。在此，我们研究毒力进化对疫情空间传播的影响。在入侵前沿的边缘，我们发现更具毒力和传播力的基因型有望在与其他病原体的竞争中胜出。然而，在前沿线之后，更为谨慎的利用策略会胜过有毒力的病原体。至关重要的是，即使有毒力突变体仅存在于前沿边缘，病原体进化也会显著改变入侵速度。我们通过基于个体的模拟来支持我们的分析，并讨论前沿线上发生的种群统计学随机性对毒力进化的额外影响。我们证实，只有当入侵病原体的承载能力足够大时，前沿才会出现毒力增加的情况。我们根据最近关于在传播疫情边缘研究毒力进化的实证研究来讨论这些结果。
