West Nile fever

Definition

A mosquito-borne viral disease caused by West Nile virus (genus Flavivirus), transmitted primarily through the bite of infected Culex mosquitoes that acquire the pathogen from avian reservoir hosts. Most human infections are asymptomatic; symptomatic cases range from mild febrile illness to severe neuroinvasive disease including meningitis and encephalitis. The disease exemplifies an arboviral zoonosis with an enzootic bird-mosquito transmission cycle and incidental spillover to humans and equids.

Etymology

Named for the West Nile district of Uganda, where the virus was first isolated from a febrile human in 1937.

Example

During summer surveillance, Culex pipiens mosquitoes collected at urban wetlands tested positive for West Nile virus RNA, signaling elevated risk of West Nile fever transmission to humans in the surrounding metropolitan area.

Synonyms

• West Nile disease

Related Terms

• Arbovirus
• vector competence
• Culex
• enzootic cycle
• neuroinvasive disease
• West Nile encephalitis
• Zoonosis

Usage Notes

Distinguished from West Nile encephalitis, which refers specifically to the neuroinvasive form; 'West Nile fever' encompasses the full clinical spectrum. The term is used in both clinical and epidemiological contexts, with public health entomologists tracking vector infection rates to predict human case risk.