Rabies is the most lethal disease known to mankind. It is essentially 100% fatal once it becomes symptomatic. I'm only aware of one ever case of someone becoming symptomatic and surviving, and that's with all the wonders of modern medicine. In D&D, I'd say that there's not likely to be any rabies vaccine or similar that exists, so medicine checks and regular doctoring won't help at all. Serious magical healing is needed, or it's the dirt nap. Shadowdweller above has a good schedule of symptoms.