
Any direct contact with an infected dog during regular walks, play, training classes etc spreads the disease. So too can their owners/handlers if they have any mucus or saliva from the dog on their hands/clothes if fussing your dog soon after contact with their own. It's an airborne virus so most commonly caught by contact with dogs sneezing or coughing close to yours and sharing water bowls at clubs and shows.
Incubation is generally 7-10 days prior to symptoms being noticed and it is at this point that the dog is most infectous as this is when the first coughing or sneezing starts. Although called KC, not all dogs ever cough hence why I mentioned sneezing. Also some can sound more like they are snuffling or choking/gagging rather than a cough.
If you're confident your lad has not been in any situations where he could have contracted the virus - discount the pup last night as a host (but forewarn the owner just in case it develops signs later also) - then better to reassess today and see the vet if signs persist as coughs can be the signs of other illnesses too.
Normally in a young (not pup!) fit and otherwise healthy dog, KC usually requires no special treatment other than cutting right back on exercise and playing as any form of excitement will exacerbate the condition. Baby cough medicine such as Benylin or Tixylix can be given to soothe the throat etc. if the dog is clearly uncomfortable.
Avoid your dog being in contact with all other dogs and regular dog dense areas until all symptoms have disappeared for at least a week. While not a particularly dangerous virus in itself (although there are many strains) KC can cause secondary infections which for newborns, the very young, otherwise infirm or very elderly dogs can prove fatal.
HTH info helps, Teri