Based on data from an array of scientific journals, the CDC, and the Center for Evidence-Based Medicine at Oxford University, Just Facts developed a methodology to estimate the number of people in the U.S. who have active infectious cases of Covid-19. These calculations, which are updated on a daily basis with a 1-to-2 day lag, find that as of December 13, 2020, roughly one of every 50 people in the U.S. has a contagious case of Covid-19. This is a national average and is not applicable everywhere because of large differences in the timing and severity of the pandemic in different areas of the country.