Summary: The problem of the spread of a non-fatal disease in a population which is assumed to have constant size over the period of the epidemic is considered. J.-H. He
’s [see Appl. Math. Comput. 156, No. 3, 591–596 (2004; Zbl 1061.65040
); ibid. 135, No. 1, 73–79 (2003; Zbl 1030.34013
)] homotopy perturbation method is employed to compute an approximation to the solution of the system of nonlinear ordinary differential equations governing the problem. The results are compared with the results obtained by the Adomian decomposition method. Some plots are presented to show the reliability and simplicity of the method.