Former US president George HW Bush is in the intensive care unit at a Texas hospital after suffering "a series of setbacks," including a stubborn fever, his spokesman said.
In a brief email Wednesday, Bush spokesman Jim McGrath said the 88-year-old had been admitted Sunday to the unit at Methodist Hospital. McGrath said Bush, the oldest living former US president, was alert and talking to medical staff.
He said doctors were cautiously optimistic about Bush's treatment and that the former president "remains in guarded condition." He said Bush was surrounded by family.
Early Thursday, McGrath told Associated Press he had no new information on Bush's condition and that he would release another statement "when events warrant it".
Bush has been hospitalized since November 23, when he was admitted for a lingering cough related to bronchitis after being in and out of the hospital for complications related to the illness.
A fever that kept Bush in the hospital over Christmas had gotten worse, and doctors had put him on a liquids-only diet Wednesday following "a series of setbacks".
"It's an elevated fever, so it's actually gone up in the last day or two," McGrath told the AP. "It's a stubborn fever that won't go away."
But he said the cough that initially brought Bush to the hospital had improved.
The former president achieved notoriety in retirement for skydiving on at least three of his birthdays since leaving the White House in 1992.
He suffers from a form of Parkinson's disease and in recent years has used a wheelchair to get around.