You mean mange? Depends on the type. Sarcoptic mange (scabies) is contagious and can infect other dogs, cats, and humans. Demodectic (demodex/red mange) is non-contagious and does not infect other animals or humans. Demodex is most often triggered by stress.
YES- mange is caused by a mite that infects mammals- that mite can get on a human, however we have the means of washing ourselves and seeking medical treatment for the infestation so it is usually not as dangerous as if it were on a wild critter.
If he got it from outside then, yes, it is most likely contagious - because he probably got it from another animal. I'd get him treated as soon as possible. It's easier for other animals to catch it, but humans are still at risk.
We aren't sure what type it is the vet said he got it from outside.