Pope Francis has bronchitis but is showing a "marked improvement" after being treated with antibiotics and could be discharged from hospital "in the coming days", medical staff said.
The update came as the 86-year-old prepared to spend a second night in Rome's Gemelli hospital, where he was admitted yesterday after complaining of breathing difficulties.
"The Holy Father was found to have an infectious bronchitis which required the administration of antibiotics", medical staff caring for him said in a statement published by the Vatican.
The treatment resulted in "a marked improvement in his state of health" and the pope "could be discharged in the coming days", it said.
Vatican spokesman Matteo Bruni said that Pope Francis, who earlier this month marked ten years as head of the Catholic Church, had spent the afternoon resting, praying and doing some work.
The Vatican initially said he had been admitted for pre-planned checks, before revealing late yesterday he had been diagnosed with a respiratory infection.
The Argentine pontiff had suffered a number of health issues throughout his life, including having part of one of his lungs removed when he was 21 years old.
While keeping a busy schedule and travelling widely, he had for the past year used a wheelchair due to knee pain, and admitted last summer he had to slow down.
His admission to hospital sparked widespread concern, particularly after unconfirmed reports that he arrived in an ambulance.
"I am touched by the many messages received in these hours and I express my gratitude for the closeness and prayer," the pope said in a message posted on Twitter.
Pope Francis was forced to cancel engagements, and there are now questions over his presence at services for the upcoming Holy Week and Easter, the most important period in the Christian calendar.
Preparations are already underway at the Vatican for this weekend's Palm Sunday celebrations.
'Always the fear'
At his weekly audience yesterday morning, just hours before his admission to hospital, the pope appeared in good spirits, smiling as he greeted the faithful from his "popemobile".
But he was pictured grimacing as he was helped getting onto the vehicle -- a photo that made all the major front pages of Italy's newspapers.
News of the pope's hospitalisation made global headlines and sparked prayers among many of the estimated 1.3 billion Catholics worldwide -- including US President Joe Biden.
Mr Biden, only the second Catholic president in US history, urged attendees at a White House reception to "say an extra prayer" for the pontiff.
His health was also on the minds of visitors to the Vatican this morning.
"There is always the fear, and yet it seems that everything is calm for now," said Tina Montalbano, a 60-year-old tourist guide.
"I hope he recovers very soon and can celebrate the Easter period here in St Peter's."
Francis was admitted in July 2021 to the same Rome hospital for ten days for an operation on his colon after suffering from a type of diverticulitis, an inflammation of pockets that develop in the lining of the intestine.
In an interview in January, the pope said the diverticulitis had returned.
Resignation rumours
Pope Francis had repeatedly said he would consider stepping down if his health required it, following the example of his predecessor Benedict XVI.
The German theologian, who died on 31 December, shocked the world in 2013 by becoming the first pope since the Middle Ages to resign.
Pope Francis had cautioned, however, that papal resignations should not be the norm, and said in an interview in February that the idea was currently not "on my agenda".
