Former-President George H.W. Bush has been in intensive care with a fever since Sunday, a spokesman said.
"He's had a series of setbacks now that have landed him in guarded condition in the intensive care unit," Jim McGrath said, according to BBC News. Doctors are cautiously optimistic about Bush's treatment and said that the former president "remains in guarded condition."
Bush, 88, has been in Methodist Hospital in Houston, Texas, since he was admitted for bronchitis treatment on November 23, BBC also noted.
More from GlobalPost: George H.W. Bush hospitalized
Details were not immediately given, reported the Associated Press, but earlier Wednesday, McGrath said a fever that kept the former president in the hospital over Christmas had gotten worse and that doctors had put him on a liquids-only diet.
Doctors at Methodist Hospital "continue to be cautiously optimistic about the current course of treatment," McGrath also said in a statement, according to Reuters. "The president is alert and conversing with medical staff, and is surrounded by family."
Bush, the 41st president of the United States, took office in 1989 and served one term in the White House, reported Reuters. He is the father of former President George W. Bush and also served as a congressman, ambassador to the United Nations, envoy to China, CIA director and vice-president for two terms under Ronald Reagan.
The former president suffers from a form of Parkinson's disease and in recent years has used a wheelchair to get around, ABC News reported.