HOUSTON (AP/CBSDFW) – A “stubborn” fever that kept former President George H.W. Bush in a hospital over Christmas has gotten worse, and doctors have put him on a liquids-only diet, his spokesman said Wednesday.

Jim McGrath, Bush’s spokesman in Houston, had said Wednesday that the fever had gone away, but he later corrected himself.

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“It’s an elevated fever, so it’s actually gone up in the last day or two,” McGrath told The Associated Press. “It’s a stubborn fever that won’t go away.”

The diet was a way to attack what doctors called “a series of setbacks.”

The 88-year-old former leader of the United States had been admitted Sunday to the ICU at Methodist Hospital.

McGrath said Bush, the oldest living former U.S. president, was alert and talking to medical staff, adding that doctors are cautiously optimistic about his treatment.

He said Bush was surrounded by family, and was only admitted to the ICU out of ‘an abundance of caution.’

Bush’s chief of staff says the former president is getting excellent medical treatment and that he would ask that people “put the harps back in the closet.”

Bush’s longtime Houston chief of staff Jean Becker says in a statement Bush will likely be in the hospital for a while.  She also urges people keep him and his family in prayers.

Doctors at Methodist Hospital in Houston have run tests and are treating the fever with Tylenol, but they still haven’t nailed down a cause, McGrath said. Doctors also have put Bush on a liquid diet, though McGrath could not say why.

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CBS News reported Bush has not responded to medication designed to lower his fever and described his condition as guarded Wednesday.

The bronchitis-like cough that initially brought Bush to the hospital on Nov. 23 has improved, McGrath said. The 88-year-old is now coughing about once a day, he said.

Robert Genzel, an emergency room doctor at Texas Health Harris Methodist in Fort Worth, says it can take a while for anyone, even a young person, to shake bronchitis.  “He’s 88, and when you’re older you don’t put up with infections as well. Most of us, bronchitis is annoying, you feel lousy, and you get over it, you’re done. The current recommendations is not even to give antibiotics.”

Bush has been in and out of the hospital for complications related to the illness, first for a week right after the election, then again the day after Thanksgiving.

Bush was visited on Christmas by his wife, Barbara, his daughter Dorothy, son Neil, and Neil’s wife, Maria, and a grandson.  The 41st president has also been visited twice by sons George W. Bush, the 43rd president, and Jeb Bush, former governor of Florida.

Bush and his wife live in Houston during the winter and spend their summers at a home in Kennebunkport, Maine.

On Thursday the Bush family asked McGrath to limit updates giving about the former president’s condition.  The family did say they had total confidence in the Doctors at Methodist Hospital and that Former First Lady Barbara Bush shares their doctor’s cautious optimism.

The former president was a naval aviator in World War II — at one point the youngest in the Navy — and was shot down over the Pacific. He achieved notoriety in retirement for skydiving on at least three of his birthdays since leaving the White House in 1992.

(©2012 CBS Local Media, a division of CBS Radio Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)

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