Kennel cough is highly contagious to other dogs and those animals being fostered must be kept isolated or be fostered in a home with no other dogs.
Kennel cough is treatable and normally runs its' course in 3 weeks unless you are dealing with extremely young dogs or older ones who may have a compromised immune system. It can then go into pneumonia which can be deadly. Your dog may exhibit no other symptoms except for a cough.
Many animals in shelters are euthanized for kennel cough because it is so contagious to the other animals. When a dog begins to exhibit the hacking cough associated with this disease, they are isolated and then killed to prevent the spread.
Which is pretty sad if you think about it.
Kennel cough can be viral or bacterial and is much like a common cold to us humans.
You can have your dog immunized against kennel cough if they are around other dogs in a kennel situation or even in areas like agility class or flyball.