2:56 Dr. Leana Wen WATCH: The importance of wearing a facemask during the coronavirus pandemic 10,456 views •May 1, 2020

The fact that guidance evolved around wearing a mask to prevent the further spread of COVID-19 is a good thing, according to public health expert, Dr. Leana Wen. In a conversation with PBS NewsHour Correspondent John Yang, she said that as more research helps us understand how this novel coronavirus behaves, the world’s knowledge and best practices about it should also evolve, forming “the cornerstone of a good public health response.” Wen answered viewer questions on May 1 about what the U.S. has learned from this coronavirus outbreak, and past pandemics.