You’ve probably seen this diagram from a Chinese study somewhere already, but in case not, give it a look. Note the position of the A/C unit.
That’s the layout of a restaurant in Guangzhou, involving an actual case of COVID-19 in late January. A1 was a patient infected with the virus who had recently arrived from Wuhan. Researchers theorize that that one person infected nine other people in the dining room that day thanks to the air conditioning unit positioned across from her. The theory is that the A/C blew the virus she was expelling back across Table B and against the wall, where it rebounded and eventually traveled all the way across to Table C. No diners on the other side of the dining room (not shown here) were infected.
The moral of the story: Confined spaces are hazardous to your health during an epidemic. Which we all already knew, but about which we’re all in some degree of denial due to our yearning to get back to normal.