Parvo is a viral infection primarily affecting the digestive tract. The most frequent symptoms are loss of appetite, vomiting and diarrhea. It can be a devastating disease especially for young puppies. One of the things that makes parvovirus a worry is that once the virus is shed from an infected dog it remains capable of infecting another dog for several months, most viruses remain infective for a matter of hours. Because of this your puppy can be exposed without even seeing another dog. Keeping your puppy away from areas frequently used by other dogs and getting his vaccinations on time until around 14 weeks of age are critical.