Then US President George W. Bush (R) waves alongside his parents, former president George Bush and former first lady Barbara Bush upon their arrival in Fort Hood, Texas, in this April 8, 2007 file photo. Barbara Bush has been hospitalized in Houston for treatment of early signs of a "respiratory-related issue," her husband's office said on Dec 31, 2013. Barbara Bush, 88, one of only two women to be both the wife and mother of US presidents, was admitted on Monday to Methodist Hospital in Houston's Texas Medical Center, the statement said. [Photo/Agencies]

HOUSTON - Former first lady Barbara Bush was in good spirits and doing well after being admitted to a Houston hospital earlier this week with a respiratory ailment, a family spokesman said on Thursday.

"She's definitely keen to get home to her dogs and her husband, and not in that order," said Jim McGrath, a spokesman for former president George H.W. Bush.

Barbara Bush, 88, was being evaluated by doctors day-to-day, and no time has been set for her discharge, McGrath said.

Former president Bush took to social media and sent a message on behalf of his wife to President Barack Obama and former president Bill Clinton in appreciation of their concern.

"Barbara thanks @BarackObama & @billclinton for their get-well wishes and is heeding their advice. Doesn't happen w every President she knows!" he said on his Twitter feed.

The former first lady was admitted on Monday to Methodist Hospital in Houston's Texas Medical Center.

Obama sent his best wishes in a statement from Hawaii where he is vacationing with his family.

Barbara Bush is known to the American public as a no-nonsense wife and mother who said she was more interested in running a household than in helping her husband run the country.

After leaving the White House, she pursued her interest in promoting literacy and reading and also wrote her memoirs.

The former first lady is also the mother of George W. Bush, the 43rd US president.