A. Without knowing for sure what it is it is hard to say. There are many skin conditions which are contagious, some are only contagious to dogs with compromised immune systems. It could be ring worm (very contagious), it could be mange )1 type is contagious, 1 is not) or it could even be caused by scratching from fleas or allergies, even injury.
I would try call hh animal control or a rescue group to see if they dog can be picked up (and hopefully treated).
Your account has been reactivated.