Sen. Robert Byrd, D-W.Va., was released from the hospital Thursday after being treated this week for what his aides called a mild infection.

Byrd, the longest serving member of the Senate, was admitted Monday after doctors discovered he had a fever and aides and his attendant noticed he was lethargic at his office on Capitol Hill.

Byrd "will complete the course of his antibiotic treatment as prescribed by his doctors at his home and is expected to return to his official Senate duties upon his doctors' approval," spokesman Jesse Jacobs said in a release.

Jacobs said Byrd talked on Wednesday with staff members, expressed he was pleased about Sen. Ted Kennedy's successful surgery to remove a brain tumor, and also asked whether Vice President Dick Cheney had apologized for a crack he made over the weekend linking incest to West Virginia. Cheney, through his staff, did apologize.

Byrd, 90, is serving his ninth term in the Senate following re-election in 2006, but has been hospitalized several times in recent months. He was taken to a hospital in February after suffering from a fall in his home. And in March, he was hospitalized following a reaction to medication.

Byrd has fended off recent attempts to remove him from his position as chairman of the Senate Appropriations Committee. In June 2007, Byrd declared: "I will continue to do this work until this old body gives out. Just don't expect that to be anytime soon."