Now that is frightening, especially in light of the fact, quoting, "People who die from this form of plague often die on the same day that symptoms first appear."
So if people don't know they have the symptoms and don't go to the doctor for treatment despite that, there's a 95% chance they'll die untreated. Did I interpret that wrong?
You didn't interpert it wrong, it says death from septicemic plague is 95% certain. By the time you reach a dr, your internal organs have begun to shut down from hemorrhaging.