In Nashville, Tenn., a sign reminds visitors to wear masks at Belmont University, which is preparing to host Thursday’s presidential debate. Federal health officials say a new study highlights the need for masks.

A sign greets visitors outside the Curb Event Center at Belmont University as preparations take place for the second Presidential debate, Tuesday, Oct. 20, 2020, in Nashville, Tenn., during the coronavirus outbreak. Governors of states including Tennessee, Oklahoma, Nebraska and North Dakota are all facing calls from doctors and public health officials to require masks. (AP Photo/Patrick Semansky)