Development of symptoms of COVID-19, infection caused by novel coronavirus depends on spread of nCoV infection in human body and also how immune system responds towards nCoV and gene expression of ACE-2 enzyme. This video presentation explains mechanism of nCoV entry into human cell, the effect of down-regulation of ACE-2 on COVID-19 and how COVID-19 affects human body. The information given in this video is obtained from journal materials and CDC.