在流行病学水平上,许多菌株之间的竞争动态的一般理论需要了解毒力的多态性,可传播性,抗生素抗性和感染原的其他生物学特性。数学共感染模型已经解决了特定的系统,专注于导致稳定共存或竞争排斥的标准,然而,由于它们的复杂性和非线性,合并感染模型中的分析解决方案仍然很少见。在这里,我们研究了2株易感感染-易感感染(SIS)室模型与共感染/共定殖,在同一框架下纳入五个应变适应度维度:传递性的变化,运输持续时间,成对共感染的敏感性,共感染持续时间,以及混合共感染的传播优先效应。利用奇异摄动方法,在应变相似性的假设下,我们揭示了慢时间尺度上的应变动力学是如何由复制方程明确控制的,该方程包含所有特征及其相互作用。这不仅可以明确预测给定的2人比赛的最终流行病学结果,但此外,它们的整个频率动力学是它们的相对变化和超越应变的全局参数的直接函数。基于相互入侵的能力,我们分析并报告了2应变系统中过渡现象的严格结果,通过地方性合并感染患病率强烈介导。我们表明,共感染并不总是共存的促进者;相反,其有利于或防止多态性的作用是非单调的,取决于菌株之间表型分化的类型和水平。这个框架提供了一个更深入的分析理解2株竞争游戏在共感染,在流行病学的理论和实际应用中,生态与进化。
A general theory for competitive dynamics among many strains at the epidemiological level is required to understand polymorphisms in virulence, transmissibility, antibiotic resistance and other biological traits of infectious agents. Mathematical coinfection models have addressed specific systems, focusing on the criteria leading to stable coexistence or competitive exclusion, however, due to their complexity and nonlinearity, analytical solutions in coinfection models remain rare. Here we study a 2-strain Susceptible-Infected-Susceptible (SIS) compartmental model with co-infection/co-colonization, incorporating five strain fitness dimensions under the same framework: variation in transmissibility, duration of carriage, pairwise susceptibilities to coinfection, coinfection duration, and transmission priority effects from mixed coinfection. Taking advantage of a singular perturbation approach, under the assumption of strain similarity, we expose how strain dynamics on a slow timescale are explicitly governed by a replicator equation which encapsulates all traits and their interplay. This allows to predict explicitly not only the final epidemiological outcome of a given 2-player competition, but moreover, their entire frequency dynamics as a direct function of their relative variation and of strain-transcending global parameters. Based on mutual invasion fitnesses, we analyze and report rigorous results on transition phenomena in the 2-strain system, strongly mediated via endemic coinfection prevalence. We show that coinfection is not always a promoter of coexistence; instead, its effect to favour or prevent polymorphism is non-monotonic and depends on the type and level of phenotypic differentiation between strains. This framework offers a deeper analytical understanding of 2-strain competitive games in coinfection, with theoretical and practical applications in epidemiology, ecology and evolution.