And the body rarely, as far as I know, forces them out the nose, no matter how immunocompetent it is. Flea infestations, incidentally, tend to peak in the fall, because the fleas have had several months to multiply. And with our long warm fall this year, the peak is even later. Winter is a good opportunity to get rid of fleas completely, because the cold weather will help. The puppies die from malnutrition.
Canine distemper is a viral infection.
The typical symptoms are a fever, loss of appetite, snotty nose, eventually pneumonia, and death. Thanks to wide spread vaccination we rarely see typical distemper. I have never seen one. But the virus is still around. I have seen dogs with nervous system disorders caused by infection with the distemper virus, apparently many years before the illness.