CDC published an article on April 2 which got more press in the last 24 hour news cycle. April 2 CDC here, new at ABC here.
In a nutshell, a restuarant in China had 5 tables with 4-10 seats. One patient (A1) at table A was COVID-positive but pre-symptomatic. 9 people in the room became positive, all in the draft line of Table A. 73 other diners on the floor, during the day, did not get sick. Those who got sick were seated for 30-60 minutes. There was no report of staff walking in and out of the room getting sick.
So this draws two lessons. COVID is really, really contagious, even to people sitting 10-15 feet away for an hour (if they were in the air-flow lines).
On the other hand, it's not infinitely contagious - not everyone in the room during that hour got sick, especially those seated further away.
|click to enlarge (CDC figure)|