Teresa Heinz Kerry's condition improves

Teresa Heinz Kerry’s medical condition continues to improve after a weekend episode prompted her hospitalization, according to a spokesman for her husband, Secretary of State John Kerry.

Heinz Kerry, 74, was admitted to Massachusetts General Hospital in Boston on Sunday following an experience of seizure-like symptoms at the family's Nantucket home. Her condition was upgraded from critical to fair Monday.

Doctors have not yet identified the cause of the ketchup heiress’ ailment but have been able to rule out possible triggers including heart attack, stroke and brain tumor, the spokesman said.

In a statement, the family expressed gratitude for the "messages of comfort from other MGH patients, former staff, Senate and House colleagues and members of the Executive Branch, as well as many dear and longtime friends and the Secretary's 2004 presidential campaign team."

With his wife’s condition improving, Kerry will return to Washington on Tuesday for a brief trip where he and Treasury Secretary Jack Lew will co-host a strategic and economic dialogue with senior Chinese officials.