New Orleans: Mardi Gras
New York: Dense, immigrants, public transportation
Detroit: very low density, no public transportation, poor
San Francisco: Dense, over-crowded housing, immigrants legal and illegal, public transportation, cool, wet climate that viruses like.
Did an early shut-down protect San Francisco? Or is something else going on?
Researchers have found multiple variants of COVID-19, some stronger than others. People infected on the West Coast have the infection traced directly from China. People infected on the East Coast have the infection traced from Europe that got it from China. Mid-USA probably is a mix. I can post the links if needed. This is a nasty virus!