Reopening Plans: Deadline Sun 2pm for Qs to be answered at Mon forums; Another Survey request (Updated)

…There is a big dispute in the scientific community, however, about both the size and the behavior of these particles, and the resolution of that question would change many recommendations about staying safe.

…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.

…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.

…All this has many practical consequences. As Marr, from Virginia Tech, says, if aerosols are crucial, we should focus as much on ventilation as we do on distancing, masks, and hand-washing, which every expert agrees are important. As the virologist Ryan McNamara of the University of North Carolina told me, all these protections stack on top of one another: The more tools we have to deploy against COVID-19, the better off we are.

Similarly, Jimenez pointed out that, when a masked person is speaking, the least safe location might be beside them or behind them, where the aerosols can escape from the mask, though ordinarily, under a droplet regime, we would consider the risk to only be in front of them. The importance of aerosols may even help explain why the disease is now exploding in the southern United States, where people often go into air-conditioned spaces to avoid the sweltering heat.

…There are two key mitigation strategies for countering poor ventilation and virus-laden aerosols indoors: We can dilute viral particles’ presence by exchanging air in the room with air from outside (and thus lowering the dose, which matters for the possibility and the severity of infection) or we can remove viral particles from the air with filters.

…Consider schools, perhaps the most fraught topic for millions. Classrooms are places of a lot of talking; children are not going to be perfect at social distancing; and the more people in a room, the more opportunities for aerosols to accumulate if the ventilation is poor. Most of these ventilation issues are addressable, sometimes by free or inexpensive methods, and sometimes by costly investments in infrastructure that should be a national priority.

Last week, I walked around the public elementary school in my neighborhood while thinking about what we could do if we took aerosol transmission more seriously. It’s a single-story building, all the classrooms have windows, some have doors that open directly to the outside, and many have a cement patio right outside. Teaching could move outdoors, at least some of the time, the way it did during the 1918 pandemic. Moreover, even when indoors or during rainy days, opening the doors and windows would greatly improve air circulation inside, especially if classrooms had fans at the windows that pushed air out.

Read: Why can’t we just have class outside?

When windows cannot be opened, classrooms could run portable HEPA filters, which are capable of trapping viruses this small, and which sell for as little as a few hundred dollars. Marr advises schools to measure airflow rates in each classroom, upgrade filters in the HVAC system to MERV 13 or higher (these are air filter grades), and aspire to meet or exceed ASHRAE (the professional society that provides HVAC guidance and standards) standards. Jimenez told me that many building-wide air-conditioning systems have a setting for how much air they take in from outside, and that it is usually minimized to be energy-efficient. During a pandemic, saving lives is more important than saving energy, so schools could, when the setting exists, crank it up to dilute the air (Jimenez persuaded his university to do that).

Jimenez also wondered why the National Guard hadn’t been deployed to set up tent schools (not sealed, but letting air in like an outdoor wedding canopy) around the country, and why the U.S. hadn’t set up the mass production of HEPA filters for every classroom and essential indoor space. Instead, one air-quality expert reported, teachers who wanted to buy portable HEPA filters were being told that they weren’t allowed to, because the CDC wasn’t recommending them. It is still difficult to get Clorox wipes in my supermarket, but I went online to check, and there is no shortage of portable HEPA filters. There is no run on them.

…Japan was expected to fail by many, as it implemented an unconventional response, bucking WHO guidelines, eschewing widespread testing, and forcing few formal lockdowns. However, Japan masked up early, focused on super-spreader events (a strategy it calls “cluster busting”), and, crucially, trained its public to focus on avoiding the three C’s—closed spaces, crowded places, and close conversations. In other words, exactly the places where airborne transmission and aerosols could pose a risk… Six months later, despite having some of the earliest outbreaks, ultradense cities, and one of the oldest populations in the world, Japan has had about 1,000 COVID-19 deaths total—which is how many the United States often has in a single day. Hong Kong, a similarly dense and subway-dependent city, has had only 24 deaths.