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Coronavirus disease 2019 (COVID-19) is an infectious disease caused by a new virus called severe acute respiratory syndrome coronavirus 2 (SARS-COV-2).To describe the spread of this infectious disease, we propose a mathematical model including some important aspects, such as the carrier and memory effects as well as the nonlinearity of incidence function.The memory effect is described by the Hattaf fractal-fractional derivative.Sufficient conditions for the existence and uniqueness of solutions are established by means of Krasnoselskii's fixed point theorem and Banach contraction.Furthermore, our results show that the proposed fractal-fractional model has one stable disease-free equilibrium when the basic reproduction number satisfiesR 0 1 and a unique stable endemic equilibrium when R 0 > 1.In addition, numerical simulations for different values of fractal and fractional orders are carried out to illustrate the theoretical results.
Mamouni et al. (Thu,) studied this question.