A dog with a mild case of infectious hepatitis has a good chance of surviving if they receive prompt treatment from a vet. A dog with a more severe infection is much less likely to survive; sadly, dogs with severe infectious hepatitis often die quickly or need to be put to sleep to stop them from suffering.
Dogs that survive infectious hepatitis are often a risk to other dogs because they shed the virus in their urine for 6-9 months after recovery. The virus can then survive in the environment for months. This is why vaccination is so important; it protects your dog from the invisible risks that other dogs can pose.