Well, I can't tell you that it is impossible... but I could say that in well over 30 years of raw feeding, I have never had that happen. I have never even heard of it happening either. I don't see it as any different to kibble fed, or dogs given dried body parts to chew on frankly. I *have* heard of cases where dogs themselves have had salmonella poisoning from those things - but not one where they've passed it to humans.
LOL - let's put things into a little perspective: this is an animal that licks its own butt, and those of other dogs. And put all sorts of nasty things in their mouths, including toys, bones, raw hides, bully sticks, etc (and those are *not* very hygenic). Raw chicken would seem to me to be the minor thing
to be concerned about
If you're really worried, you could take simple precautions such as not letting the dog lick your face for 15 minutes or so after it eats (wise anyway - dog food breath doesn't smell very nice), or even wiping the dog's mouth after meals.