Effects of heterogeneous susceptibility on epidemiological models of reinfection

This paper studies an epidemic model with heterogeneous susceptibility which generalizes the SIS (susceptible–infected–susceptible), SIR (susceptible–infected–recovered) and SIRI (susceptible–infected–recovered–infected) models. The proposed model considers the case that some infected people are susceptible again after recovery, some infected people develop immunity after infection, and some infected people are reinfected after recovery. We perform a comprehensive theoretical analysis of the model, showing that under appropriate initial conditions, delayed outbreak phenomenon occurs that can give people false impressions. Moreover, compared with the SIRI model, the proposed model exists the delayed outbreak phenomenon under more probable conditions. Finally, we present a numerical example to illustrate the effectiveness of the theoretical results.