Sen. Robert Byrd (D-W.Va.) remains in the hospital three weeks after being admitted for a mild infection, his office confirmed Friday.Byrd, 91, was admitted May 15 for a mild infection, and in the weeks since his hospitalization, the ailing Senator has developed a staph infection.Byrd’s office, in a release issued Monday, noted that the Senator “developed a staph infection during his initial hospitalization for treatment for a minor infection,— thus extending his hospital stay until further notice.“Doctors have been treating him with antibiotics for the infection and he has been responding well,— the statement added. “There has been no additional indication as to when he will be released from the hospital.—A mild infection also sent Byrd to the hospital for several days last year.He was admitted on June 2, 2008, and was released three days later on June 5.