Diarrhea, stools can be bloody with mucus, vomiting and lethargy. Never had first hand experience, but others who have will be along soon. Really needs medical attention if you suspect it.
My experience with parvovirus was with my Chocolate Lab. She was clearly very ill-acting. Vomiting everything including water and foul liquid stool. If you have a young dog and suspect Parvovirus, I would definitely get your pup to a vet. It's very easy to know if a dog has parvovirus and supportive care helps a lot.
Yes the advise above is true and if your pup is doing this and you think that's what he has he needs a vet ASAP as it can kill them if not properly treated.