On a Seir Epidemic Model with Delay (original) (raw)

We improve previous results for an SEIR-type disease transmission model with fixed latency period, standard incidence and variable population size. Infected individuals are assumed to be unable to give birth, and individuals recover from the disease and acquire permanent immunity with probability f , and dies from the disease with probability 1 − f . In particular, by a novel application of the envelope method we give a complete classification of the equilibria, we show the stability of the disease free equilibrium for R 0 < 1, and the proportional persistence of the disease for R 0 > 1.