Parvo is certainly a concern for puppies...you just don't see it nearly as much in adult dogs. There is a test for Parvo, if you bring the pup straight to the vet...it's relatively expensive though, like $100 for the test. I worry much more about distemper in adult dogs. I think it's a bit more 'catchy' for dogs that have been vaccinated for it, and it has cropped up in shelters recently.
Don't forget URIs too..not nearly as life threatening, and I've had kennel cough clear up on it's own. But Soldier got one from us being at a shelter event, and he was totally miserable, had to bring him in for antibiotic shots and fluids as it was kicking his butt. They can get pneumonia from it.