Strictly speaking, a dog can not carry the disease without being infected, however the severity of symptoms varies so much that some dogs, especially adult dogs, would appear to have no symptoms. In fact, many adult dogs show only very mild symptoms if indeed any – most dogs with severe symptoms are below 6 months of age and the most affected are below 12 weeks. There are also substantial differences in the way different breeds are affected by a parvovirus infection.

Likewise, not all cases where the symptoms (such as bloody diarrhea) match those of parvovirus are in fact caused by parvovirus and it has been known for puppies to be wrongly diagnosed: the only definitive way to identify a parvovirus infection is through a diagnostic test by your veterinarian.