What does epizootic mean?
An epizootic is an outbreak of disease that strikes many animals at once over a broad area — essentially an epidemic, but for animals rather than humans. The word functions both as a noun (the outbreak itself) and as an adjective (describing the disease or its spread). Veterinarians, wildlife biologists, and epidemiologists use it routinely when discussing events like avian influenza sweeping through poultry flocks or hemorrhagic disease moving through deer populations. Its opposite is enzootic, which describes a disease persistently present at low levels within an animal population rather than flaring up suddenly. Derived from Greek roots meaning 'upon' (epi) and 'animal' (zoon), the term entered English through the vocabulary of comparative medicine. Though uncommon in casual conversation, epizootic is valuable precisely because it fills a gap: when disease devastates wildlife or livestock on a large scale, no other single word captures that phenomenon so precisely.
A widespread outbreak of infectious disease affecting many animals at once within a given area; the animal analogue of a human epidemic.
"The state's largest recorded epizootic killed nearly half the wild turkey population in a matter of weeks."
Plural: epizootics.
Relating to, characterized by, or denoting a disease that breaks out suddenly and widely among animals.
"Rabies is considered epizootic in parts of the eastern United States where raccoon strains circulate actively."
Used when referring to multiple distinct outbreaks, either of different diseases or in different regions or time periods.
"Historical records document several devastating epizootics among cattle during the eighteenth century."
When foot-and-mouth disease ravages livestock across continents or chronic wasting disease spreads through herds of elk, scientists don't call it an epidemic — they call it an epizootic, because 'zoos' is right there in the word.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of epizootic
The word epizootic derives from the Greek epi- meaning 'upon' or 'among' combined with zōion meaning 'animal,' literally suggesting something occurring upon or among animals. It was formed on the model of epidemic, which comes from the same epi- prefix plus dēmos ('people'). The term entered English usage during the development of veterinary medicine, when scientists sought precise terminology parallel to human-disease vocabulary. It shares its zoon root with words such as zoology, zoo, and protozoan.
How epizootic is actually used
Epizootic is a technical term used primarily by veterinarians, epidemiologists, wildlife managers, and public-health officials. In everyday speech it is rare, with lay speakers more likely to say 'outbreak among animals.' The adjective use ('an epizootic event') is common in scientific literature. It should not be confused with enzootic, its opposite counterpart describing endemic-level disease in animals.
Easily confused with epizootic
An epidemic refers to a sudden, widespread occurrence of disease among humans, while an epizootic refers specifically to such an occurrence among non-human animals.
Enzootic describes a disease that is constantly present in an animal population at a stable baseline level, whereas epizootic describes an unusually widespread and often sudden animal outbreak.