Former US President George H.W. Bush was admitted to hospital on Sunday, a day after laying to rest his wife Barbra of 73 years.
His office announced on Monday that he was being treated for a blood infection.
A spokesman Jim McGrath said he is "responding to treatments and appears to be recovering."
Barbara Bush had died on Tuesday.
The 41st president greeted and shook hands with numerous attendees of the event during the invitation-only funeral. It was attended by former presidents Bill Clinton, Barack Obama, George W. Bush and their wives, along with current first lady Melania Trump.
More than a thousand people attended the ceremony.
"I always knew Barbara was the most beloved woman in the world, and in fact I used to tease her that I had a complex about that fact," Bush said after his wife's passing.
George H.W. Bush uses a wheelchair and an electric scooter for mobility after developing a form of Parkinson's disease, and he has needed hospital treatment several times in recent years for respiratory problems.
McGrath did not elaborate Monday night on the specifics of Bush's condition, saying additional updates would be issued "as events warrant." But he said he was eager to get well so he can get to his summer home in Kennebunkport, Maine.
"He's the most goal-oriented person on this planet," McGrath said.
Former Florida Gov. Jeb Bush indicated during his eulogy Saturday that his father had been hospitalized recently at the same time Barbara Bush was in the hospital for the last time. Those hospitalizations were not publicly disclosed at the time.
"I think Dad got sick on purpose so that he could be with her," Jeb Bush said.
Melania Trump tweeted Monday evening that she was sending "healing thoughts of strength, along with prayers, for President George HW Bush tonight."
