According to Google Maps Help, there is a COVID-19 layer that you can turn on in the Google Maps app on your phone. It displays the 7 day average for the number of new cases per 100,000 people. It also indicates whether cases are increasing or decreasing. More info on the Google blog.

I updated Google Maps on my phone, but it was not there in the layer list. I found this on a Google Maps Help page that new features are rolled out in stages and you might not get it right away. Perhaps it is working for you? Add a comment if you got it to work along with type of cell phone and carrier you have.

UPDATE 9/29/2020 – The COVID-19 layer magically appeared in Google Maps on my Android phone. Looks like the info is at the county level.