Parvo is a virus and is very contagious. It is spread via a fecal-oral route. Infected feces contaminate the environment and thus spread. Parvo virus is a very hardy virus that can live in the environment--yard, house, for several years. Once exposed signs usually develop within 3-10 days. This is a preventable disease--have your dogs, especially puppies and young adults vaccinated. Puppies need several parvo vaccines during development and an unvaccinated adult dog should be given a series of two boosters.