Subways, crowded high-rise public housing, big international airports, and a lot of poor immigrants.
If your county doesn’t have these, please feel free to re-open everything.
Recently I have been thinking about what it is like to live in New York. People live in tall buildings so they have to use elevators where they will share small spaces with other people. Even if they get into an empty elevator they do not know if someone was in it a minute ago. They all have to use the same door to exit and enter. Hundreds of hands touch those doors every day. It’s a petri dish.