Stability of an Age-structured SEIR Epidemic Model with Infectivity in Latent Period

We study an age-structured SEIR epidemic model with infectivity in the latent period. By using the theory and methods of Differential and Integral Equations, the explicit expression for the basic reproductive number R-0 is first derived. It is shown that the disease-free equilibrium is locally and globally asymptotically stable if R-0 < 1. It is then proved that only one endemic equilibrium exists if R-0 > 1 and its stability conditions are also given.