An exact global solution for the classical SIRSSIRS epidemic model

In this paper we propose an analytical approach to obtain an exact global solution for the classical SIRSSIRS epidemic mathematical model. The approach is based on modal expansion infinite series. These mode series are shown to provide a reliable and accurate analytical solution for the classical SIRSSIRS epidemic model. It is shown that for real initial conditions the modal expansion series present a convergent behaviour. These proposed modal expansion series do not rely on the well-known orthogonality relation. The validity and reliability of the proposed analytical approach is tested by its application in the SIRSSIRS epidemic model with various parameter values.