Fiorina's campaign said the former Hewlett-Packard Co. chief executive has been successfully treated for the infection at a Los Angeles-area hospital.
"This morning, her doctors gave her the good news that she will be released from the hospital today and can resume her busy campaign schedule tomorrow," Fiorina's chief of staff, Deborah Bowker, said in a statement. "Carly is grateful for the outpouring of well wishes and prayers from so many Californians."
The first-time candidate, who is 56, was diagnosed with breast cancer in February 2009 before she formally announced her run against Democratic Sen. Barbara Boxer. She completed chemotherapy and radiation treatments a year ago and had reconstructive surgery in July after having a double mastectomy.
Recent polls show the race between Boxer and Fiorina tightening with just six days left before the election.
A University of Southern California-Los Angeles Times poll released Sunday showed Boxer maintaining a narrow advantage, 47 percent to 41 percent, against Fiorina. The gap was smaller than the same poll showed a month ago.
Both women have maintained busy schedules criss-crossing the most populous state in the nation.
On Tuesday, Fiorina sent supporters to take her place to meet with small business owners in two Riverside County cities to discuss jobs and the economy. Supporters will again take her place at a scheduled campaign stop in San Diego on Wednesday afternoon.
Boxer, meanwhile, appeared Tuesday night with first lady Michelle Obama and Jill Biden, wife of Vice President Joe Biden, to urge Democratic supporters to grant Boxer a fourth term.
Mrs. Obama was scheduled to appear at a private lunch at a West Los Angeles home Wednesday on Boxer's behalf. Boxer was scheduled to meet with volunteers in West Hollywood in the afternoon.