A pestilence is any virulent and highly infectious disease that can cause an epidemic or even a pandemic. The word can also be used about parasites causing large scale sickness and death, such as Guinea worm.

Originally the word referred to the disease plague, which is called pestis in Latin.

The 14th-century English poet Geoffrey Chaucer spoke of “pestilence” in “The Pardoner’s Tale”, referring to the Black Death:

Ther cam a privee theef men clepeth Deeth,

That in this contree al the peple sleeth,

And with his spere he smoot his herte atwo,

And wente his wey withouten wordes mo.

He hath a thousand slayn this pestilence.