COVID-19 spreads through the air. Here's what you can do about it this winter
CBC
This is an excerpt from Second Opinion, a weekly roundup of health and medical science news emailed to subscribers every Saturday morning. If you haven't subscribed yet, you can do that by clicking here.
Canadians looking for guidance on how to reduce their risk of COVID-19 indoors this winter may be feeling left out in the cold.
The Public Health Agency of Canada (PHAC) now recommends opening windows to increase ventilation and using HEPA filters to clean indoor air, but it stops short of advocating for better-quality masks or saying outright that the virus is primarily airborne.
"From what I've seen, Canada is now an outlier in terms of not acknowledging transmission through the air," said Linsey Marr, an expert on virus transmission at Virginia Tech in Blacksburg, Va. "I think the messaging could be more clear."
Canada's guidelines on masking also haven't been updated in more than a year, with non-medical masks containing a filter still recommended — despite research showing cloth masks are less effective than surgical masks against the airborne spread of COVID-19.
"It sounds like they're still talking like there's a shortage of medical masks," said Marr, a civil and environmental engineering professor. "We know any mask is better than no mask, but also some masks are better than other masks — and so if you haven't already, you could consider upgrading your mask."
Marr said Canada is "missing out" on the opportunity to promote better protection from medical masks with higher filtration levels, such as surgical masks or N95s, but also when it comes to explaining exactly why filtration, ventilation and masking are so important.
"That's because the virus is in the air," she said. "I think if people understand that, they will be much more likely and willing to take measures that are effective at reducing transmission."
Almost two years into the pandemic, our understanding of the airborne spread of the virus has changed dramatically, with more infectious variants increasing risk and physical distancing alone not proven to be sufficient — especially indoors.
The virus can be transmitted through the air in two key ways: microscopic airborne particles called aerosols that linger in the air like smoke, or larger respiratory droplets that fall to the ground quickly (prompting the original two-metre physical-distancing guidelines).
But experts say Canada's public health guidance has struggled to keep up with the evolving science, leading to contradictory advice, such as PHAC's recommendation that physical distancing is the "best way to help prevent the spread of COVID-19."
"If that's the case, then you should be OK with being in a room with a COVID-infected person with your mask off if you are six feet apart," said Raywat Deonandan, a global health epidemiologist and associate professor at the University of Ottawa.
"If that is not the case, then you accept aerosol transmission. But the problem is, we don't have 100 per cent consensus amongst experts. So it might be confusing for people who get conflicting information."
Toronto respirologist Dr. Samir Gupta says once we realized aerosol transmission was a primary driver of the spread of the virus through the air, public health guidelines for Canadians should have followed suit.
Intelligence regarding foreign interference sometimes didn't make it to the prime minister's desk in 2021 because Canada's spy agency and the prime minister's national security adviser didn't always see eye to eye on the nature of the threat, according to a recent report from one of Canada's intelligence watchdogs.