THIS MAY BE WHAT KING NEWSOM IS WATCHING "A simple score shows how fast the coronavirus is spreading. Here's what it is for the Bay Area - That's the reproduction value, pronounced R-naught. It's an epidemiological number that, in simplest terms, represents how many people an infected individual will transmit the virus to. An R0 of 2 means that every infected person will infect two others, and those two people will each infect two more, and so on."
https://www.sfchronicle.com/bayarea/article/A-simple-score-the-R0-tells-whether-the-15271235.php