Abstract: COVID-19 is related to Coronavirus (CoV) group of positive strand single stranded RNA viruses. It replicates within host cytoplasm without entering into nucleus of host cells. Genetics of CoV reveals that many nonstructural protein and structural proteins impacts host cell protein metabolism and gene expression. After entering into various tissues including lungs it up-regulates and down-regulates some critical host genes that are related to cell cycle regulation and apoptosis. It also affects nonspecific immune system which leads to inflammation of various respiratory organs.