This disease can be transmitted among dogs in much the same way that human "colds" are transmitted among humans.
These airborne organisms will be passed from an infected dog, through the air. If an uninfected dog inhales any of these particles they will become infected themselves.
Once there, these organisms will replicate in the new dogs system, causing the dog to get ill which will then be passed on later to other uninfected dogs if left untreated. Infected dogs can spread kennel cough potentially for weeks even after seeming to have fully recovered! This is highly contagious.
Persistent coughing by itself is not lethal however it is a good idea to have your dog examined if it is coughing over a long period of time.
Persistent coughing of this type can also be connected to some very serious diseases such as cardiac disease, Blastomycosis, Valley Fever, or Heartworms.
Cough suppressants can be used to control that aggravating cough, but additional antibiotics may be needed to stop the spread of the bacteria in multiple dog households.
It is a good idea to vaccinate your dog against kennel cough. There are intranasal vaccines as well as injectable versions.
If your dog will not be coming in contact with large groups of other dogs then the decision to vaccinate or not to vaccinate your dog is up to you.