influenza

noun

in·​flu·​en·​za ˌin-(ˌ)flü-ˈen-zə How to pronounce influenza (audio)
1
a
: an acute, highly contagious, respiratory disease caused by any of three orthomyxoviruses:
(1)
or influenza A : moderate to severe influenza that in humans is marked especially by sudden onset, fever, sore throat, fatigue, muscle aches, inflammation of the respiratory mucous membranes, and cough, that has numerous variants caused by subtypes (such as H1N1, H2N2, or H3N2) of an orthomyxovirus (species Influenza A virus of the genus Influenzavirus A) infecting humans and various animals (such as birds or pigs), and that may occur in seasonal epidemics or sometimes pandemics following mutation in the causative virus
(2)
or influenza B : influenza with less severe symptoms that is caused by an orthomyxovirus (species Influenza B virus of the genus Influenzavirus B) infecting only humans and especially children and that may occur in seasonal epidemics but not pandemics
(3)
or influenza C : mild influenza that is often asymptomatic, is caused by an orthomyxovirus (species Influenza C virus of the genus Influenzavirus C) infecting only humans, and does not occur in epidemics or pandemics
b
: any of various human respiratory infections of undetermined cause
not used technically
2
: any of various virus diseases of domestic animals marked especially by fever, respiratory symptoms, and inflammation of mucous membranes

Note: All types of influenza are commonly called "the flu."

influenzal adjective
influenzal pneumonia
influenzal symptoms

Examples of influenza in a Sentence

Recent Examples on the Web The group tested virus obtained from infected cows in both mice and ferrets—the latter of which are a good model for how influenza viruses may act in people. Alice Park, TIME, 12 July 2024 In contrast, levels remain low in the country for influenza and respiratory syncytial virus, or RSV, a respiratory illness that causes cold-like symptoms. Michelle Marchante, Miami Herald, 11 July 2024 On Monday, Moderna announced that, in a Phase 3 clinical trial, its combination COVID and influenza vaccine generated stronger immune responses in older adults than individual vaccines targeting those viruses individually. Lisa Krieger, The Denver Post, 11 June 2024 In people, influenza transmits via the respiratory route. Helen Branswell, STAT, 30 May 2024 See all Example Sentences for influenza 

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'influenza.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

Italian, literally, influence, from Medieval Latin influentia; from the belief that epidemics were due to the influence of the stars

First Known Use

1743, in the meaning defined at sense 1a

Time Traveler
The first known use of influenza was in 1743

Dictionary Entries Near influenza

Cite this Entry

“Influenza.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/influenza. Accessed 23 Jul. 2024.

Kids Definition

influenza

noun
in·​flu·​en·​za ˌin-(ˌ)flü-ˈen-zə How to pronounce influenza (audio)
1
: a very contagious virus disease with fever, exhaustion, severe aches and pains, and inflammation of the respiratory tract
2
: any of various diseases of human beings or domestic animals that are usually caused by viruses and are typically marked by fever and respiratory symptoms
Etymology

from Italian influenza, literally "influence," from Latin influentia "influence," derived from earlier influere "to flow in," from in- "in, into" and fluere "to flow"

Word Origin
Originally the Italian word influenza meant what the similar-sounding word in English, influence, means: "the act or power of producing an effect indirectly." But it also had the Latin meaning of "an invisible fluid through which the stars and planets control and direct the earth and things and people on it." When epidemics raged through Europe, no one knew what the real cause was. People blamed them on evil stars working through the invisible fluid, or influence. For this reason the Italians called the disease influenza. In 1743 an epidemic very much like our modern flu began in Rome and spread. That was when the Italian word was borrowed into English. Flu is a shortened form of influenza.

Medical Definition

influenza

noun
in·​flu·​en·​za ˌin-(ˌ)flü-ˈen-zə How to pronounce influenza (audio)
1
a
: an acute, highly contagious, respiratory disease caused by any of three orthomyxoviruses:
(1)
or influenza A : moderate to severe influenza that in humans is marked especially by sudden onset, fever, sore throat, fatigue, muscle aches, inflammation of the respiratory mucous membranes, and cough, is caused by any of several subtypes (such as H1N1, H2N2, or H3N2) of an orthomyxovirus (species Influenza A virus of the genus Influenzavirus A) infecting humans and various animals (such as birds or pigs), and may occur in seasonal epidemics or sometimes pandemics following mutation of the causative virus see asian flu, avian influenza, bird flu, hong kong flu, spanish flu, swine flu, swine influenza
(2)
or influenza B : influenza with less severe symptoms that is caused by an orthomyxovirus (species Influenza B virus of the genus Influenzavirus B) infecting only humans and especially children and that may occur in seasonal epidemics but not pandemics
(3)
or influenza C : mild influenza that is often asymptomatic, is caused by an orthomyxovirus (species Influenza C virus of the genus Influenzavirus C) infecting only humans, and does not occur in epidemics or pandemics
b
: any human respiratory infection of undetermined cause
not used technically
2
: any of various viral diseases of domestic animals (as shipping fever of horses) marked especially by fever, respiratory symptoms, and inflammation of mucous membranes

Note: All types of influenza are commonly called "the flu."

influenzal adjective
influenzal pneumonia
influenzal symptoms

More from Merriam-Webster on influenza

Last Updated: - Updated example sentences
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