I always worry about fleas transmitting panleukopenia (distemper) from cat to cat while I'm trapping. I would think that a flea would easily be able to jump from one cat/kitten harboring the virus, and bite the next one and transmit the virus. Viruses are a scary aspect of our world as they are capable of mutating constantly. I'm dealing with a horrible situation with my "Wood Pile Gang". They had moderate URI symptoms a week ago, then the poop hit the fan. They developed ulcers in their mouths which is indicative of calicivirus. Then it got worse. I thought one of the four kittens had a fractured hind leg last weekend, and started making phone calls to have him seen first thing Monday. Things weren't as they seemed, and the little girl Emily developed SEVERE edema in all her legs, and her face within 36 hours of the suspected fracture! I knew it was serious and got on the internet and typed "feline calicivirus" into the search engine and knew then and there they had the "new" mutated form. It's been a hellish week to put it mildly. You brought up a very good point all around as far as cat viruses go! If anyone can find an answer I think they deserve a medal!