https://www.vox.com/recode/2020/4/21/21227855/coronavirus-spreading-by-state-instagram-effective-reproduction-rate

Calculating the rate at which the virus spreads can help show how well stay-at-home measures are working.

Over the weekend, Instagram co-founders Kevin Systrom and Mike Krieger launched rt.live, a website that calculates how fast the coronavirus is spreading in each state. This might seem like a surprising move for two people who became rich and famous for building a photo-sharing app. Then again, they also know a thing or two about metrics and algorithms.