Former first lady Barbara Bush was hospitalized Monday for early signs of pneumonia, ABC News first reported.
Jim McGrath, a spokesman for the former president, said there was "nothing new to report" on Wednesday.
"Former First Lady Barbara Bush was admitted to Methodist Hospital in Houston's Texas Medical Center yesterday for treatment on a respiratory related issue," said a release from the office of George H.W. Bush. "She is in great spirits, has already received visits from her husband and family, and is receiving fantastic care."
The statement said updates will be issued when warranted.
In a written statement Wednesday, President Barack Obama said the thoughts and prayers of all Americans are with Mrs. Bush. Obama said she is blessed to have a loving, supportive family and, in his words, a "vibrant spirit that we hope will have her feeling better soon."
Mrs. Bush, whose husband George H.W. Bush was president from 1989 to 1993, used her prominence as first lady to champion numerous civic and charitable causes, primarily as an advocate for global literacy.
Just last week, Mrs. Bush and her husband, the 41st president, honored a Houston businessman and philanthropist with a Points of Light Award, a volunteer service award started by the former president.
The Bushes' home is in Houston.
Mrs. Bush had a reputation for bluntness when her husband was president. Her son, George W. Bush, was the 43 president.
The Bush family matriarch had heart surgery in March 2009 for a severe narrowing of the main heart valve. She also was hospitalized in November 2008, when she underwent surgery for a perforated ulcer. In 2010, she was admitted to the hospital after having a mild relapse of Graves disease, a thyroid condition for which she was treated in 1989.
Health concerns had been more common of late with her 89-year-old husband, the nation's oldest living former president. George H.W. Bush was released in January 2013 after he spent nearly two months at Houston Methodist Hospital, being treated for a bronchitis-related cough and other health issues.
The Associated Press contributed to this story.