A spokesman says former U.S. President George H.W. Bush is being treated in the intensive care unit of a Houston, Texas, hospital.
Jim McGrath, a spokesman for the 41st U.S. president, said Bush, 88, was admitted to the intensive care unit "following a series of setbacks, including a persistent fever."
The spokesman said Bush was alert, conversing with medical staff, and surrounded by family members.
The illness kept Bush in the hospital over the Christmas holiday.
Bush has been hospitalized since November 23 for treatment of bronchitis-like symptoms.
Bush, the father of former President George W. Bush, served as president for a single term from 1989 to 1993.
The former vice president to President Ronald Reagan was beaten by Bill Clinton in the 1992 U.S. election.
Bush’s spokesman said doctors at Methodist Hospital had put the former president on a liquids-only diet. It was not immediately clear why that decision was made.
The statement on December 26 added that doctors are “cautiously optimistic” about the former president’s treatment. It said Bush remains in “guarded condition,” or with doctors paying careful attention to his case.
The spokesman told The Associated Press that Bush’s fever has "actually gone up in the last day or two." He described it as a "stubborn fever that won't go away."
It was reported in early 2012 that Bush had been diagnosed with lower body parkinsonism, which causes a loss of balance, and that he often uses a wheelchair.
Bush, seen as a moderate member of the Republican Party, is remembered for building an international coalition and sending U.S. troops to expel Iraqi forces from Kuwait in the 1991 Gulf War.
He also guided American policy during the tense period around the 1989 fall of the Berlin Wall and the 1991 dissolution of the Soviet Union.
Despite praise for his foreign policy leadership, Bush lost his 1992 reelection bid after he came under pressure for abandoning a pledge not to raise taxes while president.
During a lengthy career in public office, Bush also served as a Congressman from Texas, director of the CIA, the Central Intelligence Agency, and U.S. ambassador to China and the United Nations.
Bush flew as a naval aviator in World War II and was shot down over the Pacific.
After leaving the White House in 1993 and retiring from politics, he attracted attention by skydiving on at least three of his birthdays.
Bush’s eldest son, George W. Bush, was elected president in 2000 and served the maximum two terms, leaving office in early 2009 after Barack Obama was elected America’s 44th president.
Based on reporting from AFP, Reuters, and AP