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

The first recorded death from West Nile virus this year in L.A.

From Los Angeles Times • Oct. 24, 2025

The first cases of West Nile virus this year have been recorded in Los Angeles County, with four people hospitalized between July and August, officials said.

From Los Angeles Times • Sep. 18, 2025

There have been no cases of West Nile virus in humans acquired in the UK to date - though there have been seven travel-related cases since 2000.

From BBC • May 21, 2025

West Nile virus is endemic in several regions across the world, including parts of South America and Europe, and has expanded in recent years.

From BBC • May 21, 2025

Of particular concern right now are native Culex mosquitoes, which can transmit deadly West Nile virus, Diaz said.

From Los Angeles Times • May 20, 2025