July 11, 2020

HOME, SWEET HOME:

If the coronavirus is really airborne, we might be fighting it the wrong way: Airborne transmission would mean there are certain solutions we really need to focus on. (Neel V. Patel, July 11, 2020, MIT Technology Review)

One of the biggest questions we still have about covid-19 is how much of a viral load is needed to cause infection. The answer changes if we think it is aerosols that we need to worry about. Smaller particles won't carry as large a viral load as bigger ones, but because they can linger in the air for much longer, it may not matter--they'll build up in larger concentrations and get distributed more widely the longer an infected person is around to expel aerosolized virus. 

The more people you have coming in and out of an indoor space, the more likely it is that someone who is infected will show up. The longer those infected individuals spend in that space, the higher the concentration of virus in the air over time. This is particularly bad news for spaces where people congregate for hours on end, like restaurants, bars, offices, classrooms, and churches. 

Airborne transmission doesn't necessarily mean these places must stay closed (although that would be ideal). But wiping down surfaces with disinfectant, and having everyone wear masks, won't be enough. To safely reopen, these spots will not just need to reduce the number of people allowed inside at any given moment; they will also need to reduce the amount of time those people spend there. Increasing social distancing beyond six feet would also help keep people safer. 

Ventilation needs to be a higher priority too. This is going to be a big problem for older buildings that usually have worse ventilation systems, and areas with a lot of those might need to remain closed for much longer. The impact of asymptomatic spread (transmission by people who don't feel ill) and superspreaders only compounds the problem even further. But research conducted by the US Department of Homeland Security has shown that in the presence of UV light, aerosolized particles of the size the Tulane researchers studied would disappear in less than a minute. A number of businesses have begun deploying UV-armed robots to disinfect hospital rooms, shopping malls, stores, public transit stations, and more.

For many places, considerable delays in economic reopening might ultimately be the price of getting the virus under control. Otherwise the kind of thing that happened when a single open bar in Michigan led to an outbreak of more than 170 new cases could become commonplace. 

For Brosseau, the best strategy is simply to behave as we did in the early days of lockdown--stay home, and avoid coming into contact with anyone you don't live with. And if you have to leave home, she says, "all I can say is spend as little time as possible in an enclosed space, in an area that's well ventilated, with as few people as possible."

Posted by at July 11, 2020 9:02 AM

  

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