Xavier actually has divine healing abilities! He can heal any and all damage to the body, but can do little about living things (viruses included) that cause the damage. Did polio ruin your legs? He can fix your legs but you'll have to fight off the polio yourself. He can't do anything about cancer either, but if you go wild and chop out all your afflicted organs, he can fix you up right as rain.
He's not a happy person.