Which symptom is closely associated with smallpox rather than chickenpox?

Lesions appearing centripetally is a characteristic symptom closely associated with smallpox. In smallpox, the rash begins on the face and extremities and moves toward the center of the body, hence the term "centripetal." This pattern of lesion development is distinct from chickenpox, where lesions typically appear first on the trunk and then spread peripherally to the limbs.

The presence of centripetal lesions is significant because it helps differentiate smallpox from other conditions, such as chickenpox, which has a more scattered and centrifugal pattern in its rash development. Understanding this key symptom can assist in the identification and differentiation of these two diseases, which is crucial for effective diagnosis and management.