ROME (AP) — Pope Francis’ respiratory tract infection is presenting a “complex clinical picture” that will require further hospitalization, the Vatican said Monday as concerns grew about the increasingly frail health of the 88-year-old pontiff.

Vatican spokesman Matteo Bruni said the results of tests conducted in recent days and Monday indicate the pope is suffering from a “polymicrobial respiratory tract infection” that has necessitated a further change in his drug therapy. Scientists say polymicrobial diseases are caused by a mix of viruses, bacteria, fungi and parasites.

There was no timeframe given for his hospitalization, which has already sidelined him for longer than a 2023 hospitalization for pneumonia. Bruni said the complexity of his symptoms “will require an appropriate hospital stay.”

Francis was admitted to Rome’s Gemelli hospital in a “fair” condition on Friday after a weeklong bout of bronchitis worsened. Doctors confirmed a respiratory tract infection and prescribed “absolute rest” alongside unspecified drug therapies. Subsequent updates said his slight fever had gone away and that he was in “stable” condition.

Bruni said Francis, ate breakfast and read the newspapers Monday morning after a third peaceful night.

The Argentine pope, who had part of one lung removed after a pulmonary infection as a young man, is a known workaholic who keeps up a grueling pace despite his increasingly precarious health. He uses a wheelchair, walker or cane because of bad knees and suffers from sciatica nerve pain. In 2021 he had 13 inches of his colon removed because of a narrowing, and then had a further surgery in 2023 to remove intestinal scar tissue and repair an abdominal hernia.

When he had a bad case of pneumonia in 2023, he left the hospital after three days and only acknowledged after the fact that he had been admitted urgently after feeling faint and having a sharp pain in his chest. This time around, Francis insisted on finishing his morning audiences Friday before leaving the Vatican, even though he was having trouble speaking at length because he was short of breath.

Francis’ continued hospitalization has already forced the cancellation of some events connected to the Vatican’s Holy Year and put others in question. The Holy See has only confirmed canceled appointments through Monday. Francis was supposed to have gone to Rome’s Cinecitta film studios to meet with artists as part of the Catholic Church’s Holy Year celebrations.

The pope’s next scheduled appointment is his weekly general audience Wednesday. Beyond that, he is scheduled to preside on Sunday at the ordination of deacons as part of a Holy Year weekend dedicated to deacons. Francis’ participation in both appears in doubt, but they remain on the official Vatican schedule.

When he missed the Jubilee Mass dedicated to artists this past Sunday, a cardinal stood in for him.

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Medical writer Maria Cheng contributed from London.