In this book, we developed a new hybrid deterministic model, we do this by considering several essential properties of the pandemic COVID-19, such as the existence of individuals tested positive for COVID-19 with severe, mild, or asymptomatic symptoms, and dividing infectious compartment into two essential compartments of hospitalized individuals and those in intensive care units. The content of this book is divided into 3 chapters: In the first chapter, we study the stability properties of the solutions of a proposed nonlinear mathematical model with nine compartments, namely,...