Chart 2. Key clinical characteristics to differentiate between Smallpox, Monkeypox, and Varicella.

Characteristics	Monkeypox	Smallpox	Chickenpox
Causative virus	Monkeypox virus	Variola virus	Varicella zoster virus
Fever	1-3 days before the rash between 38.5°C and 40.5°C	2-4 days before the rash often >40°C	1-2 days before the rash up to 38.8°C
Initial site and lesion appearance	Face Hard and deep, well-circumscribed, umbilicated	Tongue and mouth Hard and deep, well circumscribed, umbilicated	Chest, back, and face Superficial, irregular borders, “dew drop on a rose petal”
Lesion progression	one stage of development on the body; slow progression with each stage lasting 1–2 days	one stage of development on the body; slow progression with each stage lasting 1–2 days	multiple stages of development in the body; fast progression
Lymphadenopathy	Yes	No	No
Headache	Yes	Yes	Yes
Duration of illness	2-4 weeks	Up to 5 weeks	4-7 days