You are probably thinking about parasites. If an animal has parvo, they will exhibit symptoms and have it. It's not like parasites where they can pass eggs, but not be showing signs.
Now if you are thinking parvo can be carried by other vectors and such, then yes. Parvo can be carried airborne, and fecal/oral. Meaning if a fly lands on a parvo dog's fecal material, then flies down the block into a home and lands on the food dish. Then that dog licks the dish.. bam, parvo.
I just don't think it's possible for a dog to have a dormant parvovirus and not exhibit signs or have the virus. Never seen it or heard of it?