Stability of a discrete HTLV-1/SARS-CoV-2 dual infection model

Dual infection with a virus that targets the immune system, such as HTLV-1 (human T-cell lymphotropic virus class 1), combined with another virus that affects the respiratory system, such as SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), can cause serious disease and even death. Given the significance of better comprehending the dual viral infections' dynamics, researchers have been drawn to mathematical analyses of such models. This work investigates the stability of a discrete HTLV-1/SARS-CoV-2 dual infection model. Our approach involves formulating the discrete model through the discretization of the continuous-time one using NSFD (nonstandard finite difference) method. We demonstrate that the NSFD method preserves essential properties of the solutions, such as positivity and boundedness. Additionally, we determine the fixed points and establish the conditions under which they exist. Furthermore, we analyze the global stability of these fixed points utilizing the Lyapunov technique. To illustrate our analytical findings, we do numerical simulations.