avian influenza
noun
variants
or avian flu
: highly variable influenza A of birds caused by any of several subtypes of the causative orthomyxovirus (Alphainfluenzavirus influenzae) of which some strains have been or may be transmitted to other vertebrates including humans especially after undergoing mutation
Most cases of avian influenza infection in humans have resulted from contact with infected poultry (e.g., domesticated chicken, ducks, and turkeys) or surfaces contaminated with secretion/excretions from infected birds.—
The Tennessee Tribune
compare bird flu
Examples of avian influenza in a Sentence
Recent Examples on the Web
The laboratory confirmed a positive result for highly pathogenic avian influenza Monday evening.
—Christopher Harris, CBS News, 14 Jan. 2026
This virus, known as the H5N1 strain of highly pathogenic avian influenza, was detected in a Walker County facility that housed broiler chickens, which are chickens raised for meat.
—Drew Kann, AJC.com, 14 Jan. 2026
Most recently, scientists have been monitoring the highly-pathogenic avian influenza H5N1 subtype, or bird flu.
—Patrick Jackson, The Conversation, 7 Jan. 2026
Pathologists will perform a necropsy on the mountain lions to check for abnormalities and neurological diseases like rabies and avian influenza.
—Marlene Lenthang, NBC news, 2 Jan. 2026
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Cite this Entry
“Avian influenza.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/avian%20influenza. Accessed 20 Jan. 2026.
Medical Definition
avian influenza
noun
variants
or avian flu
: influenza of birds that is caused by any of several subtypes (such as H5N2 or H7N7) of an orthomyxovirus (Alphainfluenzavirus influenzae) of which some strains have been transmitted to other vertebrates including humans especially after undergoing mutation
More than 100 species of wild waterfowl have been identified as natural, usually asymptomatic hosts of a variety of avian influenza … subtypes.—Discover
Bird flu, or H5N1 avian influenza, has been circulating across North America since 2022, infecting birds, livestock, wildlife, pets, and humans. Despite 70 documented human cases, there are no known instances of human-to-human transmission—but some scientists are starting to worry that it's only a matter of time.—Catherine Caruso, Harvard Medical School
called also fowl pest, fowl plague
see bird fluLove words? Need even more definitions?
Merriam-Webster unabridged
