In epidemiology, an epidemic (from Greek epi- upon + demos people) is a classification of a disease that appears as new cases in a given human population, during a given period, at a rate that substantially exceeds what is "expected," based on recent...

A disease is an abnormal condition of an organism that impairs bodily functions. In human beings, "disease" is often used more broadly to refer to any condition that causes discomfort, dysfunction, distress, social problems, and/or death to the person...

A pandemic (from Greek παν pan all + δήμος demos people) is an epidemic that spreads through human populations across a large region (for example a continent), or even...

List of historical plagues

Four Horsemen of the Apocalypse

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: