Variational iteration method for solving the epidemic model and the prey and predator problem

In this article two problems are considered; the first one is 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, and the other one is the problem of prey and predator. The variational iteration method is employed to compute an approximation to the solutions of the systems of nonlinear ordinary differential equations governing on these problems. The results are compared with the results obtained by Adomian decomposition and power series methods. Some plots are presented to show the reliability and simplicity of the method.