Smallpox and chickenpox

Feature

Smallpox (Variola)

Chickenpox (Varicella)

Causative

agent

Variola virus

(Orthopoxvirus)

Varicella-zoster virus; VZV

(Herpesvirus family)

Incubation

period

12 days (7-17 days)

15 days (10-21 days)

Rash

• Deep seated

• Appear in single stage

• Evolution is slow

• Superficial

• Appear in crops (Pleomorphic)

• Evolution is rapid

• Dew drop rashes

Rash
distribution

• Centrifugal

• More concentrated on
peripheral areas (Palm, Sole)

• Extensor surface

• Centripetal

• More concentrated on
central areas (Face, trunk)

• Flexor surface

Fever

Subsidies with appearance
of rash

Rise with each crop
of rash