As Pope Francis has battled double pneumonia in hospital for nearly three weeks, talk of the 88-year-old pontiff's death or resignation has become almost commonplace.

This was the pope's "third serious downturn" since he was admitted to Gemelli Polyclinic hospital with a complex respiratory infection on Feb. 14, the BBC said. The Vatican said laboratory tests suggested the mucus was a response to Francis' original pneumonia, not a new infection.

Pope Francis has stabilized enough after two respiratory crises to be taken off noninvasive mechanical ventilation and resume receiving just high flows of supplemental oxygen via a nasal tube to help him breathe,