Are two face masks better than one for stopping COVID-19?

New and more contagious COVID variants are spreading across the U.S., prompting reminders about the importance of wearing face masks. Some health experts are even encouraging people to wear two masks instead of one. CBSN's Tanya Rivero spoke with Linsey Marr, a professor of civil and environmental engineering at Virginia Tech and an expert on airborne transmission of viruses, about why it could help.