“…In other words, the description of epidemic models by using fractional differential equations takes into account all historical and current states, which makes them more realistic and more general in nature. 37 , 38 This prompted us to develop the Caputo fractional mathematical model for COVID-19 and introduce details about the existence of a unique positive solution and its behaviour. In spite of the fact that there are many definitions of a fractional derivative, many scholars prefer to use the Caputo derivative to describe mathematical models by means of FDEs.…”