Experts say more measures needed to address COVID-19 aerosol transmission

More than a year into the novel coronavirus pandemic, Canadian experts say changes are needed to address the indoor transmission of COVID-19 aerosols, tiny particles or droplets that can stay in the air.

They say the current infection control protocols in place don’t adequately help to curb the airborne transmission of COVID-19 and that officials need to pivot to target the appropriate areas, like ventilation and proper mask-wearing.

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“We just need a sort of shift in our minds of how we view the way transmission works,” said Brooks Fallis, a critical care physician and former critical care director at the William Osler Health System.

“I think people are quite fixated on hand-washing, two metres distancing and wearing some sort of face-covering … If you look at the transmission of COVID and say, ‘You acquire COVID by breathing in infected air and infected air accumulates indoors,’ I think it’s easier for people to understand how they’re getting infected.”

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Nearly two weeks ago — and after months of heated debate — the World Health Organization (WHO) acknowledged that COVID-19 can be spread through aerosols in poorly ventilated or crowded indoor spaces since the tiny particles “remain suspended in the air” and can travel more than one metre.

The Centers for Disease Control and Prevention (CDC) also recently updated its guidance on COVID-19 transmission, saying, “Transmission of SARS-CoV-2 from inhalation of virus in the air farther than six feet from an infectious source can occur.”

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While these public health organizations have only recently updated their stances on the transmission of the novel coronavirus, some experts have long believed that people could contract COVID-19 through particles that stay in the air.

“By acknowledging how COVID is mostly being transmitted, we can use the tools in the toolbox that we have to control an aerosol-transmitted disease,” said David Fisman, an epidemiology professor at the University of Toronto’s Dalla Lana School of Public Health.

“We can be more effective at disease control, and we can open up and relax some things that aren’t going to create danger for anybody.”

Outdoors remain safe, experts say

For months, experts have said the risk of outdoor COVID-19 transmission is low.

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Several studies also back up this claim, with one report saying less than 10 per cent of reported global COVID-19 cases were acquired outdoors. The same research also showed the likelihood of indoor transmission is nearly 19 times higher than outdoor spread.

“People need to understand that outdoors is safe,” Fisman said. “You’re in a well-ventilated space with a breeze blowing. It’s much harder for you to suck in the aerosol that someone else has breathed out.”


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Fisman said opening parks, playgrounds and other outdoor amenities, including patio dining if it’s properly spaced out, can be done safely.

“Because the outdoors provides an incredible naturally ventilated space, we should be leveraging that a lot more and allowing people a little bit more freedom in the outdoors while still respecting the most important thing outdoors, which would be distancing,” Fallis added.

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“Where distancing isn’t possible, wear masks.”

Proper indoor ventilation also needed

In order to mitigate indoor airborne transmission of the novel coronavirus, experts say better ventilation is needed in buildings, homes, schools and workplaces.

“This is a very old problem — we have always had this debate about many diseases, about what’s airborne and what does airborne actually mean,” said Jeffrey Siegel, a professor in the civil and mineral engineering department at the University of Toronto.

“Even without COVID, and in fact, maybe even much more than COVID, indoor air quality is a substantial problem already.”

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Siegel said ventilation needs to be addressed in many — if not most — buildings and that measures need to be put in place to protect people who need to be in close proximity with one another or without masks.

“Obviously, upgrading every ventilation system in a short period of time is not going to be possible,” Fallis said.

“There are other options, like air filtration, things like HEPA filters or filters on furnaces, that will help to remove particulate as the air is being circulated.”

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In some spaces, ventilation can’t be increased, Siegel said, and in those cases, there still needs to be strategies for reducing risk.

“It’s very specific to the building,” he added. “We have many tools in our arsenal, and it’s not a one-size-fits-all kind of approach.”

Experts say more protective masks necessary for high-risk spaces

In addition to improving ventilation, experts say people need to wear more protective masks — like N95 respirators — in high-risk indoor settings where airborne COVID-19 transmission is possible.

In particular, Fallis said people in hospitals and indoor workplaces, like warehouses or factories, need to transition to wearing a respirator-type mask.

“People need to be re-educated around mask-wearing because the current guidelines suggest that you can remove your mask in an indoor environment as long as you’re distanced from someone else by two metres,” Fallis said.


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“In a poorly-ventilated indoor space, it’s very clear that’s not appropriate guidance.”

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While some people should make the transition to wearing a respirator mask, Fisman said not everyone needs to.

“I think the people that we’re talking about are folks in the health-care environment who are overrepresented among (COVID) cases and folks who are in high-risk workplaces that are way overrepresented among cases,” he said.

“For those folks who are going to be sharing air for hours and hours and hours, yeah, absolutely they should be wearing an N95 mask. For a lot of the rest of us, when we’re doing a jaunt to a grocery store and what have you, masks still help.”

— With files from Global News’ Jamie Mauracher, Saba Aziz, David Lao and Brittany Greenslade

© 2021 Global News, a division of Corus Entertainment Inc.

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