Analysis of an SIR model: preventive measures, bounded multiplicative random perturbations and optimal control strategies.

In this paper, we study an SIR model with a nonlinear incidence rate [Formula: see text], which incorporates both a saturated incidence term and the exponential factor [Formula: see text], where μ denotes the mask-wearing rate. We derive the equilibria of the system and compute the basic reproduction number [Formula: see text]. We also investigate the local and global stability of the model equilibria. To account for environmental and behavioral variability, bounded multiplicative random perturbations are introduced into the transmission parameter [Formula: see text], and the resulting model is examined numerically under different perturbation intensities. In addition, we analyze the sensitivity of the basic reproduction number [Formula: see text]. Furthermore, Pontryagin's maximum principle is employed to determine the optimal levels of two control strategies, namely vaccination and treatment. Finally, numerical simulations are performed to illustrate the theoretical findings and support the conclusions.