(CNN) - Former President George H.W. Bush remains in an intensive care unit at a Houston hospital with a "stubborn fever that is slightly elevated," his spokesman told CNN on Wednesday.
He has been in the intensive care unit at Methodist Hospital since Sunday, spokesman Jim McGrath said, and has been hospitalized there for over a month.
McGrath said earlier Wednesday that Bush had spent Christmas with members of his family and was in good spirits.
Bush was in guarded condition and on a liquid diet that took effect with his transfer to the ICU, but McGrath could not offer more details about the reasons for the liquid diet.
Doctors were initially treating him for bronchitis and a lingering cough. More recently he had been undergoing physical therapy in preparation for returning home. He developed a fever mid- to late last week and began experiencing other complications that McGrath described as "a series of setbacks."
Bush, who at 88 is the oldest living former president, was visited yesterday by his family, including his wife Barbara, son Neil, daughter-in-law Maria and grandson Pierce. His daughter Doro is visiting him today.
"His mood is relentlessly positive and includes humorous banter with his doctor," McGrath said Wednesday morning.
McGrath said Bush's condition is slightly better today than it was yesterday.
He told CNN affiliate KPRC in Houston that Bush is "surrounded by his family, that is the best medicine and that's not the ideal way to spend Christmas, but he's playing the hand that he's been dealt."
Bush was first hospitalized November 7-19, and then was readmitted to Houston Methodist Hospital on November 23.
McGrath told KPRC that doctors' optimism he would be home before Christmas came after "he had strung together a couple of good days," but that the fever and other complications had interfered with that.
Bush said "I'm determined not to be grumpy about all of this," McGrath told KPRC.