SEIR epidemiological model with varying infectivity and infinite delay

Abstract

A new SEIR model with distributed infinite delay is derived when the infectivity depends on the age of infection. The basic reproduction number R-0, which is a threshold quantity for the stability of equilibria, is calculated. If R-0 1, then an endemic equilibrium appears which is locally asymptotically stable. Applying a permanence theorem for infinite dimensional systems, we obtain that the disease is always present when R-0 > 1