OTTAWA — Canada’s top public-health doctor says wearing a mask is a way for someone who might have COVID-19 without realizing it to keep from spreading the illness to others.

That’s a change from previous advice.

Dr. Theresa Tam says the shift 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 don’t exempt wearers from all the other measures they should take against COVID-19, including physical distancing and regular handwashing.

And Tam says medical masks still need to be preserved for front-line health workers, so cloth masks and other alternatives are the way to go.

She says a non-medical mask can reduce the chance of respiratory droplets coming into contact with others — for instance, on a bus or at the grocery store.

This report by The Canadian Press was first published April 6, 2020.