A novel strain of coronavirus, namely SARS-CoV-2 virus causes COVID-19 disease. They generally infect people around the world with mild upper respiratory infections. But it can evolve like all other viruses through mutation and become a different strain—the power and result of such mutation we have been observing since 2019. Many people who get Covid-19 have only mild symptoms. But for others, it is a severe illness. COVID-19 affects mainly people with underlying medical conditions and older adults.