Britannica
Sources used in this answer
How did variola major differ from variola minor?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
smallpox
Edward Jenner vaccinating his child against smallpox; colored engraving.
Variola major and variola minor are closely related viruses that both cause smallpox. The primary difference between them is their level of virulence:
- Variola major is the virus responsible for the classic, more severe form of smallpox.12
- Variola minor is a less-virulent form of the disease, sometimes referred to as alastrim.12
While both viruses belong to the family Poxviridae and affect only humans, variola major historically caused significantly higher mortality rates compared to the milder variola minor.12