Singular perturbation approach to stability of a SIRS epidemic system

In this paper, a new method named multiple time scales is introduced to estimate the domain of attraction of the endemic equilibrium point of J. Mena-lorca and H. W. Hethcote’s SIRS model. Simultaneously, the recurrence formulae established by S. Balint, A. Balint and V. Negru are adopted to construct Lyapunov function for the reduced system. Furthermore, the stability for the non-hyperbolic equilibrium point of the reduced system is discussed. In the end, numerical simulations are carried out.