Smallpox was an
infectious disease 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, derived from
varius ("spotted") or
varus ("pimple"). The disease was originally known in English as the "
pox" or "
red plague"; the term "smallpox" was first used in Britain in the 15th century to distinguish variola from the "great pox" (
syphilis). The last naturally occurring case of smallpox (
Variola minor) was diagnosed on 26 October 1977.