From NBC's Kelly O'Donnell
Senior aides to the Sen. Robert Byrd say the senator "has been admitted to the hospital and is expected to remain there for a few days."
Byrd was taken to the hospital this morning as a precautionary measure following a fall at his home which aides say "was likely caused by standing up too quickly."
While having no broken bones or bruises, upon examination, doctors found an elevated white-blood cell count which can be an early sign of an infection. Therefore, his doctors have determined that Byrd should remain in the hospital for antibiotic treatment and observation.
Aides say, "Senator Byrd is in good spirits and expressed his disappointment that he was unable to join all his Senate colleagues this afternoon for the biennial Senate photo."