Nadia GulAnwar ZebSalih DjilaliMazz UllahZohreh EskandariThitiporn Linitda2025-03-102025-03-102023Thermal Science354983610.2298/TSCI23S1323G2-s2.0-85163105751https://repository.dusit.ac.th//handle/123456789/4572We propose a COVID-19 mathematical model related to functional shape with square root susceptible-infected interaction. Using the Hurwitz criterion and then a graph theoretical-method for the construction of a Lyapunov function, we discuss both local and global stability. The analytical solution of the system is obtained in a special case. A non-standard finite difference scheme is then developed with the aim to obtain a proper discrete-time version of the model. Simulations show a good agreement between the proposed discretization and the results given by standard numerical methods. © 2023 Society of Thermal Engineers of Serbia Published by the Vin_a Institute of Nuclear Sciences, Belgrade, Serbia. This is an open access article distributed under the CC BY-NC-ND 4.0 terms and conditionsAll Open Access; Bronze Open AccessCOVID modelnumerical solutionsquare-root functionstability analysis non-standard finite difference schemeArticleScopus