$SEI_aI_sQRS$ epidemic model for COVID-19 by using compartmental analysis and numerical simulation

In this paper, we developed a $SEI_aI_sQRS$ epidemic model for COVID-19 by using compartmental analysis. In this article, the dynamics of COVID-19 are divided into six compartments: susceptible, exposed, asymptomatically infected, symptomatically infected, quarantined, and recovered. The positivity and boundedness of the solutions have been proven. We calculated the basic reproduction number for our model and found both disease-free and endemic equilibria. It is shown that the disease-free equilibrium is globally asymptotically stable. We explained under what conditions, the endemic equilibrium point is locally asymptotically stable. Additionally, the center manifold theorem is applied to examine whether our model undergoes a backward bifurcation at $R_0 = 1$ or not. To finish, we have confirmed our theoretical results by numerical simulation