The CDC says travelers on airplanes and public transportation like buses and subways will be required to wear face masks starting this week to curb the spread of COVID-19.

The agency issued the mask-wearing rule late Friday that builds on an order announced Jan. 21 by President Joe Biden. The 11-page CDC order takes effect just before midnight on Monday night. It makes refusal to wear a mask a violation of federal law, enforced by the Transportation Security Administration and other federal, state, and local authorities. Airlines already require masks and have banned more than 2,000 passengers for refusing to wear one.