TORONTO -- Winter is coming and it is expected to have an impact on how people transmit COVID-19.

York University microbiology associate professor Dasantila Golemi-Kotra said a big reason for the change in transmission is colder and drier air.

“This low humidity makes the virus, virus particles or respiratory droplets travel further,” Golemi-Kotra, who studies how to fight infectious diseases, said.

For example, Golemi-Kotra said, when we see our breath we are observing the large respiratory particles, but there are other tiny ones we cannot see. With more humid air, these droplets become bigger and fall to ground faster, which gets them out of harms way.

It’s why she encourages mask-use for some outdoor winter activities.

“I do skate with my daughters and sometimes it can get crowded when you skate,” Golemi-Kota said. “Check the environment, if you’re skating in a place that’s becoming crowded quickly, keep a face mask so you don’t need to worry.”

When it comes to being indoors during the winter, Golemi-Kotra said the air can be just as dry outside as in, and advises rooms be kept at a level of 40 per cent humidity.


If you don’t have a centralized humidifier in your home, she recommends using one in rooms you spend the most time in with other people and your bedroom. If you’re not sure what the humidity is, get a humidity metre to show you.

She said to further reduce the risk of COVID-19 also consider a HEPA air filter, which removes virus particles from the air.

Golemi-Kotra explained it’s important to look at your personal circumstances, such as whether your work brings you in contact with a large number of people even if you keep distance and use a mask.

“[If] at home you have elderly or people with compromised immune systems or an underlying illness, buy a HEPA air filter and keep it in their room.”

Golemi-Kotra said another element to think about in winter is our respiratory track, because with higher humidity we’re better at trapping COVID-19 and expelling particles through breathing and coughing, reducing the possibility of becoming infected.