(The New York Times News Service) -- Former President George H.W. Bush is in a Houston hospital with a lingering cough, but his doctor said Thursday he is improving and should be discharged this weekend.

Bush, 88, has bronchitis, which alternately got better and worse for a week before more sustained improvement the last few days, said Dr. Amy Myunderse, an internal medicine physician in charge of his care at The Methodist Hospital. The condition was never considered life-threatening.

"Anytime someone the president's age has bronchitis, there's concern about possible pneumonia," said Myunderse. "But Mr. Bush's condition never progressed to that level."

Bush has been in and out of Methodist for a few weeks, said his chief of staff, Jean Becker. He was admitted Nov. 7, discharged Nov. 19 and readmitted the day after Thanksgiving.

He was visited Sunday by his son, former President George W. Bush, and his wife, Laura.

Myunderse said the original cause of Bush's bronchitis was a virus, but he developed a secondary, bacterial infection.

Doctors treated Bush with intravenous antibiotics and steroids, said Myunderse. She said his cough was quite deep and caused some discomfort, but said he's had no other typical bronchitis symptoms, such as a low-grade fever or shortness of breath. She said for a time the cough sapped much of his energy, but his strength has improved in the last few days.

Myunderse said that Bush, working with a physical therapist, is sitting up, moving and walking as much as possible to help his recovery. She said he is "on target" to be discharged this weekend.

Bronchitis, an acute inflammation of the airways that carry airflow from the windpipe into the lungs, is very common among the elderly and is easily resolvable 80 percent to 90 percent of the time, said Dr. Arusha Bavare, medical director of senior services at Memorial Hermann Southwest Hospital.

Bavare said if the condition progresses to pneumonia, in which the lungs are affected, it is more serious, but she said that condition, too, is treatable.

Bush, president from 1989-1993,

has had various health problems in recent years.

In February, it was reported that he had been diagnosed with lower body parkinsonism, a condition that causes instability from the waist down. As a result, he is mostly confined to a wheelchair now.

In 2007, he was hospitalized overnight in California after he became dizzy during a round of golf on a hot day.

On Thursday, Myunderse said she was surprised at how quickly Bush is recovering.

"He is definitely in great spirits," Myunderse said in a statement. "He is happy, joking and definitely getting better."

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