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.

Pope Francis’ condition poses no immediate threat to his life though he remains at risk after a week in the hospital for treatment of pneumonia, doctors said.