Qualitative Analysis of a Time-Delay Transmission Model for COVID-19 Based on Susceptible Populations With Basic Medical History

Based on the SEIR COVID-19 epidemic model of susceptible people with basic medical histories, this paper introduces time delay, establishes a class of COVID-19 time-delay transmission model, obtains the basic reproduction number of its transmission, and determines the existence of the equilibrium point of the model. The global stability of the equilibrium point is proved by constructing the Lyapunov function and using the LaSalle invariance principle. The theoretical results are verified by numerical simulation, and the impact of different time delays on the spread of COVID-19 is discussed.