Aerosols, Too Close

I woke up this morning to a tweet from Zeynep Tufekci, who earlier pointed me to the efficacy of mask-wearing in the pandemic, talking about a study from China on droplet transmission in a restaurant. As she put it, the study supports the finding of "droplet (rather than aerosol) as key means of transmission. One asymptomatic person infected 10 (out of 91) at restaurant—but *only* if they were in direct line of air pushed by the air conditioning. (Aerosol would have infected others, too)."

The study is summarized on the CDC's website, with this as the main illustration.



The infected person is A1, highlighted in yellow. They are known to have infected the other people at their table, plus the noted people at tables B and C. The air conditioning was blowing from the vent to the right of table C, across table A toward B, with an exhaust fan then blowing the air back from B toward C.

None of the restaurant staff, notably, caught the virus from the hour or so person A1 spent in the restaurant. 

The paper discusses whether the virus would be considered as aerosolized vs. droplets (which matters a lot in the world of infectious disease), and comes to the conclusion that these were droplets. Which is good news. Distancing between tables, improvements in ventilation, and masks worn by people who think they're well (not to mention people who think they're sick, of course) would all make a difference.