I would make sure the new dog has been vaccinated for parvo.
A couple of years ago, my neighbor, whom I petsat for, was walking her dog along the side of our development where there is a field and she and Mackenzie, her dog, spotted a basset hound puppy wandering down the road. They followed the puppy and it led them to another puppy, his sister. She was sick. Mackenzie laid down beside the puppy and started licking her and whining. My neighbor flagged down a passing car and asked them to drive her up the road to Petsmart. She left the puppies at Petsmart. She found out the next day that the little female died from parvo. She was concerned about Mackenzie getting it but her vet told her that since he had been vaccinated for parvo that he'd be ok. And he was.