The effect of mild to severe illness on COVID-19 based on improved SIR modeling

Abstract

COVID-19, as a worldwide epidemic, has led to a wide range of infected individuals with negative implications for the economy, travel, and governance. Previous studies have modeled the transmission mechanism of COVID-19 based on the SIR model and its variants, where populations are categorized as susceptible, infected, and recovered. However, in clinical settings, infected individuals are further subdivided into mildly infected and severely infected individuals, and these severely infected individuals often carry viruses that are more infectious and pathogenic. To tackle the above issues, we propose a novel SI-2. We theoretically derive the disease-free equilibrium of the proposed dynamical system, as well as the basic reproduction number. The impact of the infection rate, recovery rate and mortality rate of mildly and severely infected patients on controlling the spread of the epidemic is further discussed based on the derived basic reproduction number. These results have clinical and guiding implications for the early protection and control of severely infected patients.