Dr. Theresa Tam: masks are a way for people who might have COVID-19 without realizing it to keep from spreading the illness

Canada's top public-health doctor says masks are a way for people who might have COVID-19 without realizing it to keep from spreading the illness.

Dr. Theresa Tam says the change from previous advice is due to increasing evidence that people with the virus can spread it without knowing they're sick.

She says masks worn this way protect others more than they protect the people wearing them, and she stresses that medical masks still need to be preserved for front-line health workers.

She adds that wearing a mask doesn't exempt people from other measures they should take against COVID-19, including physical distancing and regular handwashing.