"Parvo" is short for Parvoviral enteritis.  It is a highly contagious, very serious and very common viral disease in dogs that affects the digestive system.  The most common signs are vomiting, diarrhea, loss of appetite and depression.  The onset of illness is sudden, and death can occur in as little as 48-72 hours.  The virus can survive for months or years in the environment.  Vaccination provides the best chance for prevention.