[suzzer99]

Back to actual non-nonsense discussion of how to deal with this virus:

We Need to Talk About Ventilation

While waiting for my results, I checked the latest batch of announcements from companies trying to assure their customers that they were doing everything right. A major U.S. airline informed me how it was diligently sanitizing surfaces inside its planes and in terminals many times a day, without mentioning anything about the effectiveness of air circulation and filtering inside airplane cabins (pretty good, actually). A local business that operates in a somewhat cramped indoor space sent me an email about how it was “keeping clean and staying healthy,” illustrated by 10 bottles of hand sanitizer without a word on ventilation—whether it was opening windows, employing upgraded filters in its HVAC systems, or using portable HEPA filters. It seems baffling that despite mounting evidence of its importance, we are stuck practicing hygiene theater—constantly deep cleaning everything—while not noticing the air we breathe.

How is it that six months into a respiratory pandemic, we still have so little guidance about this all-important variable, the very air we breathe?

Saskia Popescu, an infectious-disease epidemiologist, emphasized to me that we should not call these “super-spreaders,” referring only to the people, but “super-spreader events,” because they seem to occur in very particular settings—an important clue. People don’t emit an equal amount of aerosols during every activity: Singing emits more than talking, which emits more than breathing. And some people could be super-emitters of aerosols. But that’s not all. The super-spreader–event triad seems to rely on three V’s: venue, ventilation, and vocalization. Most super-spreader events occur at an indoor venue, especially a poorly ventilated one (meaning air is not being exchanged, diluted, or filtered), where lots of people are talking, chanting, or singing. Some examples of where super-spreader events have taken place are restaurants, bars, clubs, choir practices, weddings, funerals, cruise ships, nursing homes, prisons, and meatpacking plants.

Strikingly, in one database of more than 1,200 super-spreader events, just one incident is classified as outdoor transmission, where a single person was infected outdoors by their jogging partner, and only 39 are classified as outdoor/indoor events, which doesn’t mean that being outdoors played a role, but it couldn’t be ruled out. The rest were all indoor events, and many involved dozens or hundreds of people at once. Other research points to the same result: Super-spreader events occur overwhelmingly in indoor environments where there are a lot of people.

As another example, you may have seen the many televised indoor events where the audience members are sitting politely distanced and masked, listening to the speaker, who is the only unmasked person in the room. Jimenez, the aerosol expert, pointed out to me that this is completely backwards, because the person who needs to be masked the most is the speaker, not the listeners. If a single mask were available in the room, we’d put it on the speaker.