Abstract
In this work, we introduce an illness-death model to study COVID-19 disease. First, a multistate model was constructed to describe the possible transitions in COVID-19 states. The parameters of the suggested model were then estimated. The model was applied later to a sample of COVID-19 patients who were treated in Al-Ahmadi Hospital in Medina, Kingdom of Saudi Arabia. We used some transitions between disease states to obtain estimates of model parameters from the patient sample data. Both survival curves and hazard curves for the patients sample were obtained, in addition to distinguishing between patients based on some of their demographic characteristics.