How does a three-layer mask protect you from COVID-19?

Doctors answer viewer questions about COVID-19 including why three-layer masks are now being recommended to protect against the virus.

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The National is CBC's flagship nightly news program, featuring the day's top stories with in-depth and original journalism, with hosts Adrienne Arsenault and Andrew Chang in Toronto, Ian Hanomansing in Vancouver and the CBC's chief political correspondent, Rosemary Barton in Ottawa.