COVID-19 is an illness caused by a novel coronavirus also known as severe acute respiratory syndrome coronavirus 2, which was first identified in the City of Wuhan, China. Since then, it has been declared as a global pandemic by the World Health Organization. The late diagnosis of COVID-19 patients makes the fast spreading of the virus across the globe. Purpose: Thus, the solution to slow down the spread of this virus would be an expert system that will be able to diagnose COVID - 19 patients and produce results instantly. This paper discusses how a knowledge-based expert system can help to diagnose or detect COVID __ampersandsignndash; 19 in the early stage itself and get the result immediately without any delay.