Final answer:
The smallpox rash first appears as a macular or papular rash three to five days after the initial symptoms. It starts on the face and then spreads to the trunk and extremities.
Step-by-step explanation:
The smallpox rash first appears as a macular or papular rash three to five days after the initial cold-like symptoms and high fever. It typically starts on the face and then spreads to the trunk and extremities. The rash consists of raised bumps that turn into fluid-filled blisters, which eventually crust over and scab. The location and progression of the rash are key diagnostic features of smallpox.