Pope Francis is being treated in hospital for double pneumonia — but what is this condition, and why might the pope be particularly vulnerable to it?

Pope Francis is responding “positively” to medical treatment for pneumonia, according to the Vatican, a week after the 88-year-old pontiff was hospitalized in Rome.

"Is he out of danger? No. But if the question is 'is he in danger of death,' the answer is 'no," said the doctor of Pope Francis.