What Is Smallpox?

Smallpox is an infectious disease unique to humans, caused by either of two virus variants, Variola major and Variola minor. The disease is also known by the Latin names Variola or Variola vera, which is a derivative of the Latin varius, meaning spotted, or varus, meaning "pimple".

People infected with smallpox develop some symptoms (e.g., fever, headache, backache, and general fatigue) that are typical of many less serious diseases. However, the tell-tale sign is the development of a unique skin rash. The rash, which has a unique indentation at its centre, covers the entire body.

The rash progresses to a raised bump, then to a pus-filled blister that crusts and scabs over before finally falling off about 3 weeks later, leaving behind a pitted scar.

Smallpox spreads from person to person mainly by aerosolized droplets that come from the coughing of infected patients. Contact with smallpox scabs or contaminated clothing or linens can also spread the disease. Animals or insects are not known to act as reservoirs or transmit the disease.