The two-hour 16-minute briefing – the longest yet – started and ended with a discussion of the economy. In between was a back-and-forth about masks and an impassioned plea from Dr. Deborah Birx for people to take seriously the federal guidelines. Had Americans in certain "hotspot" cities heeded those warnings earlier, she intimated, the infection and mortality curves could have been flatter.

Major is joined by Dr. Ali Mokdad, a University of Washington professor working on COVID-19 infection modeling.

A recommendation about wearing masks will be issued in the coming days. Birx said she does not want people to have a false sense of security with a mask on and ignore social distancing and hand-washing protocol.