|Parvovirus - Wikimedia Commons file|
The feline panleukopenia virus is highly contagious and "is present wherever there are susceptible animals" (1). Wild cats, mink, ferrets and monk serve as a reservoir.
Cats that are immune to reinfection can shed the virus for weeks. There are asymptomatic carriers (infected animals with no symptoms). This causes repeated exposure in a group of cats. This can actually boost immunity in cats that are already immune through antibodies.
Kittens can be infected before birth. For these kittens mortality rate is 90%. It can cause brain damage in kittens.
Read more: Feline Distemper Symptom and Panleuk or Feline Distemper.
Note: (1) Cat Owner's Home Veterinary Handbook ISBN 978-0-470-09530-0