Bass, 30, is 0-0 with a 0.63 ERA in 14 relief appearances. He has allowed only one earned run in 14 1/3 innings.
The Chicago Tribune reported that Bass has contracted hand-foot-and-mouth disease, an infectious illness that can lead to painful spots on the skin. The move is retroactive to July 5, one day after his most recent appearance.
Norwood, 24, never has pitched in the big leagues. The Cubs' seventh-round pick out of St. Louis University in 2014 started the season with Double-A Tennessee before being promoted to the highest level of the minors last month. He pitched 5 1/3 scoreless innings with Iowa and limited opposing hitters to a .158 batting average.
--Field Level Media