More threads by David Baxter PhD

David Baxter PhD

Late Founder
Winter will help COVID-19 spread more easily, experts say — here's what they suggest you do about it
CBC News
Nov 7, 2020


When a virus is exhaled, it begins to break down right away. But the colder it gets, the slower that process is, says a Toronto epidemiologist — and that may help the coronavirus that causes COVID-19 spread. (Sean Kilpatrick/The Canadian Press)

Canada is heading into its first winter of the COVID-19 pandemic, and some experts say the change in seasons will serve the coronavirus that causes the illness well.

Cold weather affects viruses themselves in two major ways: through temperature and humidity, says Dr. Colin Furness, an infection control epidemiologist and assistant professor at the University of Toronto's faculty of information.

When a virus is exhaled, it begins to break down right away, Furness says. But the colder it gets, the slower that process is.

"Instead of dying, perhaps, in minutes on a hot summer day, in freezing temperatures, it will last essentially — as far as we know — indefinitely," Furness said. "It goes from being quick-dying to being immortal, based on temperature."

Winter weather can also help the virus stay aloft longer and travel farther, he says — because of the drier air that typically comes with lower temperatures, and how that affects the respiratory droplets we exhale.

"When the droplet you exhale comes out in humid weather … it gets bigger. It attracts water and falls to the ground," Furness said. "But in really dry, cold air, the opposite happens. The droplet evaporates, it gets lighter, and that happens very fast."

What settings are a higher risk for COVID-19 transmission? 6:11

Two infectious disease doctors answer viewer questions about high-risk settings for COVID-19 transmission and how data about transmission could help people make decisions about how to live their lives. 6:11

Then there's the effect the weather has on people.

Cold weather pushes people indoors, Furness says. It also means we don't have our windows open, meaning our living spaces won't be as well ventilated as they are at other times of year.

"If you have enough people in a poorly enough ventilated space, [like] holiday time in the winter ... that's sort of the perfect storm for virus transmission," he said.

"It pushes people exactly to where the virus moves very, very well — between people in close quarters."

The dry air also makes our bodies more vulnerable to pathogens, such as the new coronavirus, by drying out the protective mucous membrane that lines our respiratory tracts, said Dr. Dasantila Golemi-Kotra, an expert on microbial infections.

"This mucous membrane actually traps these pathogens, and as the air moves out, these pathogens are expelled," said Golemi-Kotra, who is also an associate professor in York University's biology department.

"At low humidity, this membrane becomes dry … so it's much easier, now, for the pathogens to get access to the respiratory tract and infect us."

That's the bad news. Here's what these experts suggest you can do about it.

Mind your mittens
"First of all, avoid touching your face with mittens," Golemi-Kotra said.

Your gloves or mittens could come into contact with a lot of high-touch surfaces as you go about your day, so be careful with them. Gauge your daily activities and treat your mitts or gloves accordingly, she advised.


Cold weather pushes people into spaces that are often crowded and poorly ventilated — environments where 'the virus moves very, very well,' says Dr. Colin Furness. (Trevor Brine/CBC)

If you don't wear them long or contact many high-touch surfaces, it's enough to let them sit for several hours in a safe area before re-wearing, she said. Studies show the virus's stability in porous materials like cotton is low, she said — around three hours. If your mittens are wet, the effect of drying out has also been shown to reduce the virus's stability.

But if you're wearing gloves or mitts for long stretches of time or coming in contact with many high-touch surfaces — if you work outside, for example, or have a long commute on public transit — you should wash them daily, she said.

You could also throw winter gear in the dryer, Furness suggests. He argues it's unnecessary to go the full washing route, since a dryer's heat can kill most or all of the virus.

If you're certain your gloves are all natural fibres, you could even stick them in the microwave, he adds.

"You need to make sure there's no synthetics in there," Furness said. "Mittens don't come with a label that says 'microwave safe.' But if you know, for example, that they're all wool … then the microwave would be great."

Get your flu shot
If you've never gotten a flu shot before, Furness says this is the year to start. It's a critical tool to help contain flu season and keep pressure off health systems — plus, getting sick from the flu could make your body more vulnerable to COVID-19.

To keep yourself healthy, Golemi-Kotra also recommends using a humidifier in your home or office to help counteract the effect of dry winter air on your mucous membrane and boost your immune defence.


Getting a flu shot is important, since getting the seasonal disease can make your body more vulnerable to COVID-19, according to some experts. (Tara Walton/The Canadian Press)

Not all experts are confident consumer humidifiers will make much of a difference. Dr. Christopher Labos, an epidemiologist and cardiologist, told CBC News earlier this month the positive effect may not be significant, although he said it's not likely to have a significant negative effect, either.

"This virus is very contagious, and we are looking at any measures that can sort of reduce the transmission or reduce the exposure," Golemi-Kotra said.

Scarves likely OK over masks, but wet masks not effective
If you're wearing a mask and a scarf at the same time, Furness says it should be fine to let your scarf cover the mask. But he stopped short of saying a scarf could stand in for a mask, even if worn correctly.

"There are scarves you can see through and there are scarves that are heavy knit," he said. "The answer … will depend entirely on how the scarf is made."

There's still a lot scientists don't know about how homemade masks will perform in winter, Furness says.

Some research suggests a wet mask may be less effective, Golemi-Kotra says, so condensation from your breath outdoors could be an issue. Outside, physical distancing should lower your risk even without a mask's protection, she says, but being mindful of a wet mask is something to keep in mind if you're at a crowded bus stop, for example. Make sure you stay two metres apart from others.

Until the data on masks in winter comes in, Furness seconds the advice for extra caution.

"I think, ultimately, what the second wave is going to look like is going to be very much dependent on how effective masks are as temperatures drop," he said.

"I think until we have more data, I would like to urge everyone to be just really cautious, you know, to take that extra couple of feet, step back when you're hanging around outdoors — to not assume that what was safe in the summer is safe in the winter."
Replying is not possible. This forum is only available as an archive.