Abstract
Very recently an extension of the concept of rate of change was suggested, with the aim to depict more real world problems that could not be depicted due to the limitation of the existing rate of change definition. One of the particular discovery in this is the existence of a derivative associate to Riemann-Stieltjes integral, a connection that has never been presented before. The global differential operator with its associat integral have now constructed a new calculus that is an extension of former calculus based on existing rate of change. To further see the application of this new extension, we investigated in this paper, a lassa fever model using the global differentiation in local and nonlocal sense. Existence and uniqueness conditions were verified using the theorem suggesting the linear growth and Lipschitz conditions. A numerical scheme based on the Newton polynomial was used to solve numerically the obtained models and some simulations presented.