The evidence that type of transmission is happening with SARS-CoV-2 arguably already exists. Several big studies point to airborne transmission of the virus as an important route for the spread of covid-19. Other studies have suggested the virus can remain in aerosolized droplets all night. One new study light emitting diode by Roy and his team at Tulane implies that infectious aerosolized particles of SARS-CoV-2 could actually linger in the air for up to 16 hours, and continue maintaining infectivity considerably longer than MERS and SARS-CoV-1 (the other big coronaviruses to emerge this century).
We still don’t know what gives SARS-CoV-2 this airborne edge. “But it may be one reason this is a pandemic, and not simply a small outbreak like any other coronavirus,” says Roy.
How to keep safe
Whether the virus is airborne isn’t merely a scientific question. If it is, it could imply that in places where the virus will not be properly contained (e.g., the US), the economy needs to be reopened more slowly, under tighter regulations that reinforce current health practices along with introducing improved ones. Our current tactics for stopping the spread won’t be enough.
Roy wish to see aggressive mandates on strict mask use for anybody leaving home. “This virus sheds like crazy,” that he says. “Masking can do an incredible amount in breaking transmission. I think anything that can promote the use of masking, to stop the production of aerosols in the environment, would be helpful.”
Brosseau, however, says that though masks can limit the spread of larger particles, they truly are less ideal for smaller ones, especially if they can fit only loosely. “I wish we would stop relying on the idea that face coverings are going to solve everything and help flatten the curve,” she says. “It’s magical thinking—it’s not going to happen.” For masks to really make a difference, they might need to be worn all the time, even around family.
Brosseau does believe the evidence is trending toward the conclusion that airborne transmission is “the primary and possibly most important mode of transmission for SARS-CoV-2.” She says, “I think the amount of time and effort devoted to sanitizing every single surface over and over and over again has been a huge waste of time. We don’t need to worry so much about cleaning every single surface we touch.” Instead, the focus should be on other facets, like where we spend our time.
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 concern yourself with. Smaller particles won’t carry as large a viral load as bigger ones, but since 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 individuals you have coming in and out of an indoor space, the much more likely it is that a person who is infected will arrive. The longer those infected individuals spend in that space, the higher the concentration of virus in the air with time. This is particularly bad news for spaces where people congregate for hours at a stretch, like restaurants, bars, offices, classrooms, and churches.
Airborne transmission doesn’t indicate these places must stay closed (although that would be ideal). But wiping down surfaces with disinfectant, and having everybody wear masks, won’t be enough. To safely reopen, these spots will not simply need to reduce the number of people allowed inside at any given moment; they are going to also need to reduce the timeframe those people spend there. Increasing social distancing beyond six feet would also help to keep people safer.
Ventilation needs to be a higher priority too. This is planning to be a large problem for older buildings that usually have worse ventilation systems, and areas with a lot of those might need certainly to remain closed for considerably longer. The impact of asymptomatic spread (transmission by individuals who don’t feel ill) and superspreaders only compounds the problem 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 under a minute. A number of businesses have begun deploying UV-armed robots to disinfect hospital rooms, shopping malls, stores, public transit stations, and much more.
For many places, considerable delays in economic reopening might ultimately be the price of getting the virus in order. Otherwise the kind of thing that happened when a single open bar in Michigan led to an outbreak greater than 170 new cases could become commonplace.
For Brosseau, the most useful strategy is simply to become we did in the early days of lockdown—stay home, and avoid entering contact with anybody you don’t live with. And when 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.”