"Herman Cain -- our boss, our friend, like a father to so many of us -- has passed away," it said. "He's entering the presence of the Savior he's served as an associate minister at Antioch Baptist Church in Atlanta for, and preparing for his reward."
Cain, who ran for the Republican presidential nomination in 2012, said last month he'd tested positive and was hospitalized two days later.
The Trump campaign said before the event that six staffers had tested positive.
A statement on Cain's Twitter account after his diagnosis said there's "no way of knowing for sure how or where" he picked up virus.
The former Godfather's Pizza CEO was briefly considered a front-runner in the 2012 GOP field. He ultimately suspended his campaign amid accusations he had a 13-year extramarital affair with an Atlanta businesswoman, which he denied.
Cain survived a battle with late-stage colon cancer a year earlier. He is survived by his wife, Gloria Etchison, and two children.