Former President Bill Clinton has been hospitalized in Washington after he developed a fever, a top aide told NBC News on Monday.

Clinton, 78, "has been admitted to MedStar Georgetown University Hospital for testing and observation after developing a fever," said Angel Ureña, Clinton's deputy chief of staff.

"He is in good spirits and grateful for the care he is receiving," Ureña said.

A source close to Clinton, the 42nd president, said the situation is "not urgent."

"The former president will be fine," the source said. "He developed a fever and wanted to be checked out. He is awake and alert."

Clinton has faced a number of health scares since he left office in 2001.

He underwent a quadruple bypass operation at NewYork-Presbyterian Hospital in 2004 and returned to the same hospital for another heart procedure in 2010, when two stents were inserted into a coronary artery.

He was also hospitalized for six days in California in 2021 with a urological infection that spread to his bloodstream.

Clinton campaigned vigorously for Democratic presidential nominee Kamala Harris this year and recently released a memoir about his post-presidential life.

Clinton has spoken at every Democratic National Convention since 1976, including this August.

"I want to say this from the bottom of my heart," he said in that address. "I have no idea how many more of these I'll be able to come to."