influenza

American  

[in-floo-en-zuh] / ˌɪn fluˈɛn zə /

noun

• influenzas
  plural

1. Pathology. an acute, commonly epidemic disease, occurring in several forms, caused by numerous rapidly mutating viral strains and characterized by respiratory symptoms and general prostration.

2. Veterinary Pathology. an acute, contagious disease occurring in horses and swine, characterized by fever, depression, and catarrhal inflammations of the eyes, nasal passages, and bronchi, and caused by a virus.

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influenza British  

/ ˌɪnflʊˈɛnzə /

noun

1. Also called: grippe, flu. informal a highly contagious and often epidemic viral disease characterized by fever, prostration, muscular aches and pains, and inflammation of the respiratory passages

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influenza Scientific  

/ ĭn′flo̅o̅-ĕn′zə /

1. A highly contagious infectious disease that is caused by any of various viruses of the family Orthomyxoviridae and is characterized by fever, respiratory symptoms, fatigue, and muscle pain. It commonly occurs in epidemics, one of which killed 20 million people between 1917 and 1919.

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influenza Cultural  

1. Commonly called the flu; an acute and infectious disease of the respiratory system caused by a virus and characterized by fever, muscle pain, headache, and inflammation of the mucous membranes in the respiratory tract.

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Word History

Since ancient times, influenza has periodically swept the world. Until recently, people could not tell how this illness, which we call the flu, could spread so widely. Before people knew that organisms cause disease, they thought the stars influenced the spread of influenza. Influenza comes ultimately from the Latin word influentia, meaning “influence of the stars.” Today, however, the stars are no longer blamed for the flu. Inhaling influenza viruses causes the spread of the illness.

Other Word Forms

Derived Forms

• influenzal
  adjective
• influenzalike
  adjective
• postinfluenzal
  adjective

Inflected Forms

Nouns

• influenzas
  plural

Etymology

Origin of influenza

1735–45; < Italian < Medieval Latin influentia influence

Compare meaning

How does influenza compare to similar and commonly confused words? Explore the most common comparisons:

• parainfluenza vs. influenza

Explanation

An influenza is a contagious viral infection. Influenzas tend to spread during the winter, and they're more commonly known as the flu. If you've ever wondered why this word looks so much like influence, that’s because both come from the Italian influentia. The original idea was a flowing in — of ethereal fluid from the heavens, thus affecting human destiny. We know now influenza is caused by viruses, not heavenly fluid. When you have an influenza, you're likely to vomit, have diarrhea, be exhausted, and feel terrible overall. One way to prevent influenza is by getting a flu shot.

Example Sentences

See Examples For:

influenza influenzas

In the 2025-26 flu season, the county recorded 126 influenza deaths, a relatively low total, she noted.

From Los Angeles Times ● Oct. 8, 2026

Flu hit early last winter, with a new mutated version of the virus circulating - a seasonal influenza called subclade K or Super-K.

From BBC ● Aug. 31, 2026

Australian wildlife workers have launched an unprecedented effort to vaccinate wild populations of little penguins against the highly contagious H5N1 avian influenza.

From Barron's ● Aug. 20, 2026

The agency finally clears a melanoma drug and an mRNA influenza vaccine.

From The Wall Street Journal ● Aug. 6, 2026

The principal recorded killers were smallpox, influenza, measles, typhoid, typhus, chicken pox, whooping cough, tuberculosis, and syphilis.

From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond

The fresh mutations have happened in a group of H3N2 influenzas.

From BBC ● Nov. 8, 2025

Human contact with nonhuman animals accounts for our influenzas as well, which usually emerge from wild aquatic birds.

From New York Times ● Jul. 25, 2023

That’s because avian and swine influenzas have caused pandemics in humans, including the 1918 flu pandemic, which was caused by a virus that originated in birds, and the 2009 swine flu pandemic.

From Scientific American ● Apr. 24, 2023

“In the last 20 years we’ve had many of these pathogens emerge or re-emerge: SARS, MERS, different avian influenzas, Zika, yellow fever and of course SARS-CoV-2,” van Kerkhove said.

From Reuters ● Aug. 20, 2021

Mrs. Temperly talked a great deal about the health of their friends; she seemed to keep the record of the influenzas and neuralgias of a numerous and susceptible circle.

From A London Life and Other Tales by Henry James

Related Words

• contagion
• curse
• epidemic
• infection
• infestation
• invasion
• outbreak
• pandemic
• scourge