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

Emily Burton, conservation manager, said: "Gannet populations have suffered significant declines, and many colonies are still recovering from the impacts of avian influenza."

From BBC ● Aug. 3, 2026

Seasonal influenza causes 3-5 million cases of severe illness worldwide each year and is linked to as many as 650,000 deaths.

From Science Daily ● Jul. 21, 2026

"Larger studies will be needed to determine whether spermidine can consistently improve vaccine responses and whether similar effects are seen with other vaccines, such as those used against seasonal influenza."

From Science Daily ● Jul. 21, 2026

The twins had received vaccines for hepatitis A, influenza, and DTaP, which includes diphtheria, tetanus and pertussis vaccines, during their 18-month wellness visit at their pediatrician’s office in April 2025, according to the civil suit.

From The Wall Street Journal ● Jul. 8, 2026

I rang up her doctor, who came round at once and diagnosed the usual influenza.

From "Rebecca" by Daphne du Maurier

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

Food standards bodies advise that avian influenzas pose a very low food safety risk for UK consumers.

From BBC ● Nov. 25, 2022

“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

She has offered me her little residence at Brompton for my dwelling for a week or so, to restore me from all my influenzas : she may truly be called a faithful family friend.

From The Diary and Letters of Madame D'Arblay — Volume 3 by Fanny Burney

Related Words

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