His way of thinking is wrong though. Yes he was young and healthy. Yes probably if he caught the disease, he probably wouldn't die because of his vitality. But the thing is, what about the family of the man. Were all of them healthy? Did they have an underlying medical condition which might make them more vulnerable. What of the people on the plane, at the airport, in taxis, in hotels, in restaurants, in stores that the man would come in contact with. The man at the airport might not get horribly sick, but he had contacted so many people on his holiday. Maybe they weren't quite as healthy. And who knows how many other people these service people might infect.