The 74-year-old Henry County resident, who ran for president in 2012, has been hosting a radio show on his website and recently began hosting a TV show on conservative TV outlet NewsMaxTV.
He previously worked at news/talk WSB radio for several years and was a syndicated host from 2013 to 2017.
Trump last year briefly considered placing Cain on the board of the Federal Reserve.
Dan Calabrese, editor of hermancain.com, wrote in a post today that "people will speculate about the Tulsa rally, but Herman did a lot of traveling the past week, including to Arizona where cases are spiking. I don't think there's any way to trace this to the one specific contact that caused him to be infected. We'll never know."