The Competing Two-Strain SIS Pairwise Approximation Model With Infection Age

This paper studies a two-strain SIS pairwise approximation model with a competing mechanism and non-Markovian recovery process in which the recovery rate depends on infection age. The model is a hyperbolic system, which can be transformed into a system of integro-differential equations by using the method of characteristics. We obtain the associated reproduction numbers for each of the two strains, which determine the existence of the boundary equilibria. Besides, we also show that the two competing strains may coexist.