Final answer:
The smallpox rash was known to first appear on the face, later spreading to other body parts.
Step-by-step explanation:
The nurse should teach that the smallpox rash is expected to first appear on the face. Smallpox, a disease that has now been eradicated globally, was marked by a distinctive rash that initially appeared on the face before spreading to other parts of the body. Unlike chickenpox, which typically starts with a rash on the trunk, or measles, which also begins on the face and then spreads, smallpox was notorious for its facial rash onset.