WASHINGTON - Teresa Heinz Kerry, the wife of Secretary of State John Kerry who suffered a seizure on Sunday, has been transferred to a Boston rehabilitation hospital after doctors said her conditions had further improved, the State Department said on Thursday.Heinz Kerry, 74, was rushed to a hospital on Nantucket island off mainland Massachusetts on Sunday and flown to Boston's Massachusetts General Hospital, where she was treated for seizure-like symptoms.Glen Johnson, a department official who acts as Kerry's personal spokesman, said Kerry will split his time between Boston and Washington and resume his official travel schedule soon. Since his appointment in February as Washington's top diplomat, Kerry has maintained a busy travel schedule, dealing with Syria's civil war and trying to restart Israeli-Palestinian peace talks.