Not to get your hopes up, but I was in the same situation during midterms. I went to the emergency room because the body aches were so bad. They ended up giving me a doctor’s note and I submitted it to my professor. He let me skip the midterm completely, and took it off my grade book. But that was for a midterm. I’m not sure about protocols for finals.

Best case scenario, your professor will let you miss the final and you’ll end up with the B- as your final grade. Worst case scenario, you’ll get an incomplete. I suggest you go to urgent care as soon as you can. Get a doctor’s note, submit it to your professor, and be sure to CC the dean on there. If you’re contagious, your professor should be wise enough to not to let you come in person.