It's Flu season for hoomans and for puppers too.
The bay area has had an outbreak recently and Chicago has been a hot spot for dog flu for a while.
The goods news is the flu is not that bad for dogs (low-mortality rate and often they get a mild version), but knowing is half the battle... yea yea yea, "sure mom".
There are two strains of the dog flu in the US, a vaccine for each, and it doesn't change from year to year like it does for people.
Mild symptoms include a dry or wet cough, nasal discharge and will last 10-30 days. More severe symptoms include a fever and the development of pneumonia. Other symptoms also include sneezing, lethargy, lack of appetite, and a runny nose.
Dog flu isn't quite as deadly as the human flu can be, but is still cause for concern. Warn your vet if you think your pup has the flu before going into the clinic with your pup and risking contaminating other puppers. Cross contamination is pretty easy (barking, couching, sneezing) and the virus van be carried on shoes, transmitted through water bowls, etc.
If your dog has an active lifestyle around other puppers, goes to the dog park a lot, in boarding or kennels, then the vaccine is probably best (avoid these areas during break out periods). In the bay area at least, each vaccine costs about ~$60 at the vet, and $30-40 at the store.
In tangent, there's also a rattlesnake venom vaccine for dogs. At best, it will slow down the effect of the venom and it doesn't cover all species of rattle snake venom, but it's an extra safety layer if your pup is an outdoor enthusiast and a curious one at that. It will generally buy you time to take your pup to a vet but it may not even work.