He may not be infected at all. For the next few days, be sure and walk him on a leash so that he is not exposed to any fecal matter from the other dogs. You also need to clean all common areas with a bleach solution.
Give him pedialyte instead of water and see the vet if you see diarrhea or vomiting.
Your vet can give him a parvo test and let you know if he has parvo. It's a simple test and doesn't cost very much if that's the route you want to go.
Let me know if you still have questions.