West Nile virus

American  

noun

Pathology.

1. an illness caused by a chiefly mosquito-borne virus of the genus Flavivirus, characterized in a small percentage of infected persons by fever, headache, muscle weakness, and sometimes encephalitis or meningitis.

2. the virus that causes this illness.

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West Nile virus Scientific  

/ wĕstnīl /

1. An infectious disease caused by a virus of the genus Flavivirus, occurring in Africa, Asia, the Mediterranean, and parts of North America. The infection is transmitted by a mosquito and can cause mild illness as well as severe, sometimes fatal encephalitis and meningitis.

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Etymology

Origin of West Nile virus

First recorded in 1935–40; named after the West Nile region of Uganda

Example Sentences

See Examples For:

West Nile virus

He wrote in 2024 about a bout with West Nile virus that left him in the hospital and struggling to remember facts.

From The Wall Street Journal ● Jul. 31, 2026

There is no specific treatment for West Nile virus.

From Los Angeles Times ● Jul. 8, 2026

West Nile virus is the most common and serious mosquito-borne disease in California that can be fatal to humans and some wildlife, according to the California Department of Public Health.

From Los Angeles Times ● Jul. 8, 2026

But this year, it’s found West Nile virus in 38 mosquito pools.

From Los Angeles Times ● Jul. 8, 2026

He had developed a neuroinvasive disease as a complication from contracting West Nile virus.

From MarketWatch ● Jul. 7, 2026