https://techcrunch.com/2020/04/18/instagram-founders-rt-live/

Instagram founders Kevin Systrom and Mike Krieger have teamed up to launch their first product together since leaving the Facebook mothership. Rt.live is an up-to-date tracker of how fast COVID-19 is spreading in each state.

“Rt” measures the average number of people who become infected by an infectious person. The higher above the number 1, the faster COVID-19 races through a population, while a number below one shows the virus receding. For example, Rt.live displays that Georgia has the highest, most dangerous Rt score of 1.5 while New York is down to 0.54 thanks to aggressive shelter-in-place orders.