Impact of Intracellular Delays and Target-Cell Dynamics on In Vivo Viral Infections

The dynamics of an in-host model with general form of target-cell dynamics, nonlinear incidence, and distributed delay are investigated. The model can describe the in vivo infection dynamics of many viruses such as HIV-I, HCV, and HBV. We derive the basic reproduction number R0 for the viral infection and establish that the global dynamics are completely determined by the values of R0: if R0 ≤ 1, the infection-free equilibrium is globally asymptotically stable, and the virus is cleared; if R0 > 1, then the infection persists, and the chronic-infection equilibrium is globally asymptotically stable. An implication of our results is that intracellular delays will lead to periodic oscillations in in-host models only with the right kind of target-cell dynamics.