Bush. 88, who was admitted to the intensive care unit at Methodist Hospital Sunday, has been fighting a fever. He has been in the hospital for more than a month.
The Houston Chronicle reported Jim McGrath, Bush's Houston spokesman, said Bush's fever rose Wednesday but doctors report he was doing better Thursday. The newspaper said the fever is being treated with Tylenol, but it is not responding to the treatment.
"He is considered in guarded condition," McGrath said. "He has suffered a series of setbacks."
McGrath was unsure what caused the fever but the former president is alert and engaging in a "running banter'' with his nurses and is surrounded by family, the Chronicle reported.
Bush has had health problems in recent years -- in February he was diagnosed with lower body Parkinsonism, a condition that causes instability from the waist down, causing him to use a wheelchair; and Nov. 7 he was admitted to the hospital for a bronchitis-like cough, though he was discharged Nov. 19.
The former president spent Christmas in the hospital with his wife, Barbara, and several family members who live in Houston, the Chronicle reported.
Two of his sons, former President George W. Bush and former Florida Gov. Jeb Bush, have visited him, the report said.