Smallpox is a serious, highly infectious disease that was once very deadly. It starts with symptoms similar to flu which disappear after the appearance of the characteristic rash.
With intensifying rash, high temperature returns, too. Survivors remain with diverse scars (from the rash).
This disease is now eradicated thanks to a successful vaccination campaign throughout the world. Vaccination against smallpox is no longer necessary in most countries, and in 1980 the World Health Organization declared the disease officially eradicated.
The smallpox virus still exist only in medical laboratories where it is used for research.