The number of Covid-19 cases in the world and the United States. Virus risk group. SARS-CoV-2 is the virus that causes the new coronavirus Covid-19. The confirmed cases range from mild to severe, and Covid-19 of each severity is subdivided every day. Covid-19 affects our mental health. The method used to trace or track covid-19. Test for coronavirus. Finally, the Covid-19 vaccine showed promise in early research.