I agree with Julie's analogy to day care. My cats live in a bubble, they are inside cats and only go out for Vet visits so they have zero exposure. That is why I take precautions when returning from a show. The shows are not inherently dangerous. The cats that are shown can get exposed to sniffles and such and build an immunity to it just as a child who attends public school builds more immunity than one who is entirely home-schooled. Shows are also self-policing because each cat is personally handled by six to twelve professional and trained judges, a cat showing any sign of illness would be DQ'ed and would have to leave the show hall.