VATICAN CITY — Pope Francis’s health worsened significantly Friday afternoon as his respiratory condition was irritated and necessitated the return of mechanical ventilation.

Earlier in the day, the pontiff “experienced an isolated episode of bronchospasm,” according to the Holy See Press Office.

“This led to an episode of vomiting with aspiration and a sudden worsening of his respiratory condition,” a spokesperson explained, drastically reversing what had been a steady recovery for several days.

“The Holy Father was promptly subjected to bronchial aspiration and initiated on non-invasive mechanical ventilation, which resulted in a good response in terms of gas exchange,” according to the Holy See Press Office. “He has remained alert and oriented at all times, cooperating with therapeutic maneuvers.”

Pope Francis’s prognosis “remains reserved,” doctors say.

This news has deflated a growing optimism among faithful in Rome who have been encouraged by days of cautiously positive reports coming out of Gemelli Polyclinic, where the pope is being treated.

The pontiff reportedly had even been tending to small administrative tasks from his hospital room, sitting up in an armchair and eating solid food.

He has not been seen or photographed since the respiratory health crisis began nearly two weeks ago.

The Holy See Press Office, known as the Sala Stampa, is updating reporters twice a day on the pope’s condition.

Its statements are issued only in Italian but are translated into various languages by Vatican News, an official news outlet of the Holy See.

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Throughout the ordeal, Pope Francis has been receiving daily the Eucharist, the central sacrament of the Catholic Church believed to be the literal body and blood of Jesus Christ.

Catholic clerics and lay faithful have gathered each night in St. Peter’s Square to recite the rosary for the sake of the pope, being led in their prayer by members of the College of Cardinals.