All individuals transition through various life stages over the course of their development and nearly all organisms must contend with infectious disease at some point in their lives. Yet the intersection of these two universal features of life—stage structure and infectious disease—and their joint effects on population dynamics are poorly understood. Here, we develop a two-stage population model in which density dependence acts on juvenile maturation, and infectious disease affects either juveniles or adults via reduction in maturation, reproduction, or survival. In the absence of disease, this form of density dependence can generate persistent population oscillations. We examine whether infectious disease further accentuates these oscillations (by augmenting their amplitude) or stabilizes them (by reducing their amplitude). We find that, for moderate transmission rates (a proxy for disease incidence), disease can stabilize dynamics. In contrast, fast disease transmission is not generally stabilizing, which is, at least in part, due to disease overexploitation of the infectious class. Hydra effects are possible in the model due to density overcompensation and occur when disease increases juvenile mortality or decreases adult fecundity (but do not occur when disease augments adult mortality or reduces maturation). Slow maturation, large disease-free population size, and strong density-dependent population regulation can each lower the transmission rate required for the infectious disease to invade the population.

Graphical abstract

中文翻译：

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当成长的痛苦和病假发生碰撞：传染病可以稳定阶段结构引起的宿主种群振荡

所有个体在其发育过程中都会经历不同的生命阶段，几乎所有生物都必须在其生命的某个阶段与传染病作斗争。然而，生命的这两个普遍特征——阶段结构和传染病——的交集以及它们对人口动态的联合影响却知之甚少。在这里，我们开发了一个两阶段人口模型，其中密度依赖性作用于青少年的成熟，而传染病通过减少成熟、繁殖或存活来影响青少年或成年人。在没有疾病的情况下，这种形式的密度依赖性会产生持续的种群波动。我们检查传染病是否进一步加剧了这些振荡（通过增加它们的幅度）或稳定它们（通过降低它们的幅度）。我们发现，对于中等传播率（疾病发病率的代表），疾病可以稳定动态。相比之下，快速的疾病传播通常不稳定，这至少部分是由于传染性类别的疾病过度开发。由于密度过度补偿，模型中可能出现九头蛇效应，并且在疾病增加青少年死亡率或降低成人繁殖力时发生（但在疾病增加成人死亡率或降低成熟度时不会发生）。成熟缓慢、无病人群规模大、人口密度依赖性强，都可以降低传染病侵入人群所需的传播率。至少部分是由于传染性类别的疾病过度开发。由于密度过度补偿，模型中可能出现九头蛇效应，并且在疾病增加青少年死亡率或降低成人繁殖力时发生（但在疾病增加成人死亡率或降低成熟度时不会发生）。成熟缓慢、无病人群规模大、人口密度依赖性强，都可以降低传染病侵入人群所需的传播率。至少部分是由于传染性类别的疾病过度开发。由于密度过度补偿，模型中可能出现九头蛇效应，并且在疾病增加青少年死亡率或降低成人繁殖力时发生（但在疾病增加成人死亡率或降低成熟度时不会发生）。成熟缓慢、无病人群规模大、人口密度依赖性强，都可以降低传染病侵入人群所需的传播率。

图形概要