Abstract
We study the global dynamics of delayed pathogen infection models with immune impairment. Both pathogen-to-susceptible and infected-to-susceptible transmissions have been considered. Bilinear and saturated incidence rates are considered in the first and second model, respectively. We drive the basic reproduction parameter R-0 which determines the global dynamics of models. Using Lyapunov method, we established the global stability of the models' steady states. The theoretical results are confirmed by numerical simulations. (c) 2018 Author(s).