考虑到传染病传播过程中宿主体内病毒载量和医疗资源有限对疾病传播的影响，提出一类具有饱和治疗率的宿主体内和宿主之间耦合的多尺度传染病模型。首先，对于宿主之间疾病传播模型，通过计算得到基本再生数，并给出刻画其无病平衡点和地方病平衡点的存在性与稳定性的判别准则。特别地，当基本再生数小于1时，模型存在两个地方病平衡点，其中一个局部渐近稳定，另一个不稳定。当基本再生数大于1时，模型存在唯一的地方病平衡点，它在特定条件下是全局渐近稳定的。其次，探讨医疗资源有限导致的前向/后向分支的存在性，这意味着疾病的消除或流行不再取决于基本再生数，而是与感染者的初始状态以及医疗资源的供应密切相关。最后，通过数值模拟解释了本文的主要理论结果。

Considering the influence of the viral load in the host and limited medical resources on the transmission of infectious diseases, a multi-scale infectious disease model with saturated treatment rate coupling within-host and between-host dynamics is proposed. Firstly, for the between-host disease transmission model, the basic reproduction number is obtained, and a criterion describing the existence and stability of the disease-free and endemic equilibrium for the coupled model is given. Particularly, when the basic reproduction number is less than 1, the model has two endemic equilibria, one of which is locally asymptotically stable and the other is unstable. When the basic reproduction number is greater than 1, the model has a unique endemic equilibrium, which is global asymptotically stable under specific conditions. In addition, The existence of forward/backward bifurcation caused by limited medical resources is analyzed. This means that the elimination or prevalence of the disease no longer depends on the basic reproduction number but is closely related to the initial state of infected humans and the supply of medical resources. Finally, the main theoretical results of this paper are explained by numerical simulation.