When I visit other countries it feels weird that nobody says anything when people sneeze. But I realize that's a cultural thing and try to avoid saying "Bless you".
In east Asia it's customary for sick people to wear masks to avoid spreading disease via coughing or sneezing. A practice that ought to be adopted everywhere.
I know I'm promoting a passive-aggressive strategy which is also social corrosive, but it's a way of spreading (!) the meme. And don't say "Gesundheit" because you think "bless you" is religious -- saying Gesundheit is simply non-denominationally superstitious.
It's a tradition, not a superstition.
Toughen up people!
We don't eat food off the floor because it would probably give us a bad stomach. Eating "hygienically" is a practice that we have adopted.
Dogs eat stuff off the floor all the time. Have they evolved a more advanced immune system than ours? Or just kept it well trained?
As for their immune system, inbreeding of dogs has caused all sorts of susceptibilities, though overall humans are a better vector for disease (density, widespread distribution, gregariousness, etc). Also humans worry about disease symptoms that dogs and other animals stoically ignore and thus the disease can go unnoticed by the human. (e.g. a bit of diarrhoea dribbling uncontrollably out your backside will probably concern you but a dog will just put up with it -- though an owner will likely object!) .
correct answer to that is "not in your lifetime" (from the joke about a very old very rich grandpa who sneezes and his relatives :)