On August 20, a man died of presumed Guillain-Barré syndrome. Within 90 minutes of his death, his eyes were removed and refrigerated. The following day, a cornea from one eye was transplanted into the right eye of a woman. The woman's postoperative course was uneventful until 30 days after the transplant, when she developed right retroorbital headache. Over the next few days her headache worsened, and she developed neurologic symptoms on the right side of her face and difficulty walking. She was hospitalized on September 27. Thereafter she developed flaccid paralysis, had loss of mental acuity, and died on October 10. Serum collected on October 2 was negative for rabies antibody, but serum collected on October 5 had a 23 titer. 

Answer the following problems with brief responses:

What is the etiology of this disease? 15% value

Identify the periods of incubation, prodromal, illness, and decline. 70% value
What is the mode of transmission? 15% value