Which feature distinguishes smallpox from varicella during an outbreak?

• A. Fever is absent and lesions appear in crops in various stages
• B. Classic, deep-seated vesicles in the same stage across the body with a centrifugal spread and fever preceding rash
• C. Varicella lesions have centrifugal spread and uniform stages
• D. Smallpox lesions are limited to the face and hands only

Answer: (B)

The feature being tested is how to tell smallpox apart from varicella during an outbreak by how the rash evolves and where it appears on the body. Smallpox classically presents with deep-seated vesicles that are at the same stage of development across the body, meaning you see vesicles, then pustules, then crusts all happening roughly together in different areas. Fever typically starts before the rash, and the distribution is centrifugal—more pronounced on the face and limbs than on the trunk. This combination—synchronous, deep lesions with fever preceding rash and a face/extremities–predominant spread—distinguishes smallpox from varicella.

Varicella, by contrast, shows lesions that develop in crops and are at multiple different stages simultaneously, with shallow vesicles that can crust over in a variety of places at once. The distribution is centripetal (more on the trunk), not the face and extremities, which helps differentiate it from smallpox. The other options describe features that align more with varicella or are inaccurate for smallpox, so they don’t fit the distinguishing pattern as well.