Positivity-preserving and elementary stable nonstandard method for a COVID-19 SIR model

The main purpose of this work is to build a numerical method for solving an epidemiological model that describes the spread of COVID-19 in some countries. The method is constructed using a NonStandard Finite Difference (NSFD) discretization for the analyzed model, in order to preserve its positivity and equilibrium points properties. Numerical simulations testify the best performance of the proposed scheme with respect to the related Standard Finite Difference (SFD) method, the famous explicit four-stage order-four Runge-Kutta known as RK4, and another positivity-preserving nonstandard method.