Saskia Popescu, an infectious disease epidemiologist at the University of Arizona, is one of three authors of the color-coded COVID-19 Risk Index. Popescu simultaneously released it on Twitter, where it has been liked more than 2,300 times. "We wanted people to understand, as life opens up, that there is a range of possible risks, and there are things you can do to stay safe, and things you might want to avoid," Popescu said.