It remains unclear how long Pope Francis will remain in hospital as he seeks treatment for a respiratory tract infection.

Pope Francis’s respiratory tract infection has presented a “complex clinical picture” requiring further hospitalisation, the Vatican says.

Vatican spokesman Matteo Bruni said on Monday that the pope is suffering from a “polymicrobial respiratory tract infection” that has necessitated a change in his drug therapy.

There was no timeframe given for his hospitalisation, which has already sidelined Francis for longer than a 2023 hospitalisation for pneumonia.

Bruni said the complexity of his symptoms “will require an appropriate hospital stay” and the pope was “in good spirits”.

Concerns about the 88-year-old pontiff’s health have increased since his admission to Gemelli Hospital in Rome, Italy, on Friday after a weeklong bout of bronchitis worsened.

Pope Francis’s hospitalisation has already forced the cancellation of some events connected with the Vatican’s Jubilee Holy Year and put others in question.

The Vatican said the pope’s planned weekly audience in St Peter’s Square on Wednesday had been cancelled due to his continued stay in hospital.

The pope’s doctors had earlier ordered complete rest, and Francis was unable to deliver his regular weekly prayer on Sunday to pilgrims in St Peter’s Square or lead a Mass for artists to mark the Catholic Church’s Jubilee Year.

Pilgrims visiting the Vatican on Monday offered their hopes for the pope’s recovery.

“We certainly wish for him to get better very quickly,” said Reverend Tyler Carter, a Catholic priest from the United States.

“He is our father and our shepherd, and so we want his continued health and blessing.”

Manuel Rossi, a tourist from the Italian city of Milan, said he was “quite worried” when the pope cancelled his appearance on Sunday.

“I am 18 years old, so I have seen a few popes in my life and am very close to him,” Rossi said.

“I hope he recovers as soon as possible.”

Francis had part of one lung removed after a pulmonary infection as a young man.

The Argentinian pope is a known workaholic despite his increasingly precarious health.

In addition to his frequent bouts of respiratory infections in winter, he uses a wheelchair, walker or cane because of bad knees and suffers from sciatica nerve pain.