Distinction of Smallpox from Chickenpox

Feature

Smallpox (Variola)

Chickenpox (Varicella)

prodrome before onset of rash

febrile prodrome 1-4 days before rash, often severe

none or mild

lesions

deep, firm, well-circumscribed vesicles or pustules; may be confluent or umbilicated

usually superficial vesicles

rash location

concentrated on face and distal extremities (centrifugal)

concentrated on trunk and proximal extremities (and/or face and scalp)

stage of lesions

same stage on any one part of the body

crops of lesions, with lesions in different stages of evolution (papules, vesicles, crusts)

first lesions

oral mucosa or palate (enanthem), followed by rash of face or forearm (exanthem)

first lesions on trunk, occasionally face

lesions on palms and soles

common

very uncommon

itchiness

sometimes during scabbing stage

usually intense

evolution of lesions from macules to crusts

over several days

< 24 hours

duration of illness

14 – 21 days

4 – 7 days