The new Pope has daunting challenges ahead, ranging from the church sex abuse scandal to reinvigorating the flock.
And the 76-year-old Francis will have to do it all with just one whole lung.
The Argentine pontiff underwent surgery as a young man to remove "a good part" of an infected lung, according to his authorised biographer, Sergio Rubin. "He feels it today", says Rubin. "He's a little bit slowed by it, but he's OK."
Doctors said that losing part of a lung doesn't necessarily compromise the Pope's health or reduce his lifespan, though it means no strenuous exercise since he no longer has as much air capacity as people with two lungs. "He probably wouldn't be able to run marathons, but I don't think that would be on his schedule," said Dr Peter Openshaw, director of the Centre for Respiratory Infection at Imperial College London. "Having one lung should be enough as long as there is no other disease in that lung."
It was initially reported that Francis lost an entire lung, but the Vatican said yesterday that he had only lost part of one. It provided no further details.