Fly ball is crazy barely controlled chaos from the spectators view point. I find it hard to believe there aren’t fights all the time, but it sure is fun to watch.
Dog flu has been talked about within the conformation circles too. It seems that unless you have a very old or very young dog or a dog that is already ill, the canine flu isn’t much to worry about.
The ladies on my flyball team work and train PAWS with a Cause dogs, and also have a breeder program onsite, so they don't take any chances with any diseases. My new dog, even though she is fully vetted, isn't allowed to come to flyball practice for two weeks, just to make sure she isn't carrying something.
As for the dog flu, no cases reported in Michigan but vets can get vaccines if needed.