Impact of population size and movement on the persistence of a two-strain infectious disease

This article studies the asymptotic profiles of coexistence endemic equilibrium solutions of a two-strain reaction-diffusion epidemic model with mass-action incidence when the diffusion rates are sufficiently small. We address the question of how the population size and environmental heterogeneity impact the persistence and extinction of the disease when the diffusion rates approach zero. In particular, we show that there is a sharp critical number which depends delicately on the infected groups' diffusion rates and each strain's spatially heterogeneous infection and recovery rates. Moreover, if the total size of the population is kept below this critical number, then the disease could be eradicated by restricting the susceptible hosts' movement . However, if the total population exceeds this critical number, the disease may persist no matter how the movement of the susceptible hosts is controlled. Additionally, our results suggest that the disease may persist if the diffusion rates of the infected groups are kept sufficiently smaller than that of the susceptible group.