Thirty-four states and Washington, D.C., have issued some form of a mask mandate in recent months.
Mask-wearing is just one of several steps the nation's top health officials say will pay off.
Dr. Robert Redfield, the head of the CDC, issued this warning in an interview with WebMD this week.
"For your country right now and for the war that we're in against COVID, I'm asking you to do four simple things. Wear a mask, social distance, wash your hands, and be smart about crowds. You do those four things, it will bring this outbreak down. But if we don't do that, as I said last April, this could be the worst fall from a public health perspective, we've ever had," he said.