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

Last week, local and federal public health officials reported West Nile virus activity as being well above average for this time of the year.

From Los Angeles Times ● Jul. 13, 2026

Authorities find West Nile virus by capturing and testing mosquitoes in groups of 10 to 50 each, which they call a “mosquito pool.”

From Los Angeles Times ● Jul. 8, 2026

About 1 out of 10 people who develop severe West Nile virus disease affecting the brain and nervous system die, according to the CDC.

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

About 1 out of 10 people who develop severe West Nile virus disease affecting the brain and nervous system die.

From Los Angeles Times ● Jun. 30, 2026