“Wear a mask.” It’s about as simple as advice gets when it comes to curbing the spread of COVID-19. And yet, people still aren’t listening.
Something tells me those people haven’t yet seen this new visualization, produced by The New York Times. It demonstrates what happens when you sneeze on the subway, with and without a mask. And, spoiler: Sneezing with a mask on is still not ideal, but sneezing without a mask on is an explosion of aerosol. It fills half the car with droplets, which churn through the air at face level, and coat surfaces so effectively that they trace the silhouettes of the seats.
The entire visual story does an admirable job of walking you through how air moves through the cabin of a New York MTA car. And truthfully, the protections are better than I had imagined. While 75% of the air inside a car is filtered and recirculated at any given moment, by pumping in fresh air constantly, the car gets completely new air every three minutes and 20 seconds. That’s about twice the rate of fresh air circulation on an airplane and three times the rate of your office. Relative to much of our environment and transportation options, subway cars sound downright safe on paper!
But as MIT researchers concluded in April (PDF), New York subways were “a major disseminator—if not the principal transmission vehicle” of COVID-19’s spread through the city’s population. And this new particle visualization is a powerful demonstration of how that MIT claim doesn’t just seem like a reasonable conclusion on how COVID-19 tore through NY, but an inevitable one.
We see here how a single sneeze coats the car in SARS-CoV-2 virus, which is scary. But imagine if several people on the car are sick at once, as a single MTA car can have a capacity of 250 people. Masks really are the last line of defense in a space that is already having its air filtered and replaced so frequently.
I wish more people would look at these particle visualizations to get a clear look at the spread of an invisible enemy, and how much a mask can make a difference. This earlier model that shows how COVID-19 can spread through talking—a full 20 feet in a slight breeze—has changed my entire outlook on the pandemic. We both need to wear masks and to continue social distancing at the same time (and frankly, we need another lockdown if we want either of those gestures to matter much). Because what we’ve done in the U.S. so far has clearly not worked to contain COVID-19. And looking at any particle simulation will do a whole lot to instantly explain why.