To understand infectious disease dynamics, we need to understand the inextricably intertwined nature of the ecology and evolution of pathogens and hosts. Epidemiological dynamics of many infectious diseases have highlighted the importance of considering the demographics of the societies in which they spread, particularly with respect to age structure. In addition, the waves of the recent COVID-19 pandemic driven by variant replacements at an unprecedented speed show that it is vital to consider the evolutionary aspects. The classic trade-off theory of virulence addresses aspects of pathogen evolution, but here we explore in more detail the possibility of society-specific evolutionarily stable strategies (ESS) during an unfolding pandemic. Theory posits the existence under some conditions of an ESS representing the evolutionary endpoint of change. By using a demographically realistic model incorporating infection rates that vary with age, we outline which evolutionary scenarios are plausible. Focusing on the rate of infection and duration of infectivity, we ask whether an ESS exists, what characterizes it, and as a result which long-term public-health consequences may be expected. We demonstrate that the ESS of an evolving pathogen depends upon the background age-dependent frailty and mortality rates. Our findings shed important light on the plausible long-term trajectories of highly evolvable novel pathogens.

中文翻译：

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年龄结构宿主种群中的流行病进化稳定策略


要了解传染病的动态，我们需要了解生态学以及病原体和宿主的进化密不可分的交织性质。许多传染病的流行病学动态凸显了考虑其传播社会的人口统计数据的重要性，尤其是在年龄结构方面。此外，最近由变体替换以前所未有的速度推动的 COVID-19 大流行浪潮表明，考虑进化方面至关重要。经典的毒力权衡理论涉及病原体进化的各个方面，但在这里我们更详细地探讨了在不断蔓延的大流行期间，针对社会的进化稳定策略 （ESS） 的可能性。理论假设在某些条件下存在代表变化进化终点的 ESS。通过使用一个人口统计学上现实的模型，结合随年龄变化的感染率，我们概述了哪些进化情景是合理的。着眼于感染率和感染持续时间，我们询问 ESS 是否存在，它的特点是什么，以及因此可能会产生哪些长期公共卫生后果。我们证明，进化病原体的 ESS 取决于背景年龄依赖性虚弱和死亡率。我们的研究结果为高度可进化的新型病原体的合理长期轨迹提供了重要启示。