Unfortunately, this type of virus can be reactive: poor puppy suffers a couple of days due to respiratory condition or doesn't show any sign of distress and dies eventually. (snowyswan.com)
I am a Veterinarian Technician, and foster a lot of the special cases, so I was contacted to go pick up this little poor puppy. (wagbrag.com)
Common causes are poor puppy socialization, being taken from the litter too soon, fear and poor obedience training. (houstonpettalk.com)