Houston AP

Former President George Bush was admitted to the intensive care unit of Methodist Hospital "following a series of setbacks including a persistent fever," but he is alert and talking to medical staff, his spokesman said Wednesday.

Jim McGrath, Bush's spokesman in Houston, said in a brief email message that Bush was admitted to the ICU at Methodist Hospital on Sunday. He said doctors are cautiously optimistic about his treatment and that the former president "remains in guarded condition."

The 88-year-old has been hospitalized since Nov. 23, when he was admitted for a lingering cough related to bronchitis after having been in and out of the hospital for complications related to the illness.

Earlier Wednesday, McGrath said a fever that kept Bush in the hospital over Christmas had deteriorated and that doctors had put him on a liquids-only diet. "It's an elevated fever, so it's actually gone up in the last day or two," McGrath said. "It's a stubborn fever that won't go away."

But he said the cough that initially brought Bush to the hospital has improved.

Bush was visited on Christmas Day by his wife, Barbara, his son Neil and his wife, Maria, and a grandson, according to McGrath. Bush's daughter, Dorothy, was expected to arrive Wednesday in Houston from Bethesda, Maryland. The 41st president also has been visited twice by his sons George W. Bush, the 43rd president, and Jeb Bush, the ex-governor of Florida.

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