West Nile virus

Pictures

Picture	Title	Caption	Copyright
Title Virions Caption Electron micrograph of West Nile virions. Original magnification was approx. 50,000X. Scale bar in photo represents 300 nm. Copyright Diagnostic Virology Laboratory of the National Veterinary Services Laboratory, VS, APHIS, USDA.	Virions	Electron micrograph of West Nile virions. Original magnification was approx. 50,000X. Scale bar in photo represents 300 nm.	Diagnostic Virology Laboratory of the National Veterinary Services Laboratory, VS, APHIS, USDA.
Title Eggs Caption Culex quinquefasciatus (southern house mosquito); egg raft. USA. Copyright Public Domain/released by CDC (Centers for Disease Control and Prevention) - Original photograph by Harry Weinburgh	Eggs	Culex quinquefasciatus (southern house mosquito); egg raft. USA.	Public Domain/released by CDC (Centers for Disease Control and Prevention) - Original photograph by Harry Weinburgh
Title Female Aedes mosquito Caption Aedes albopictus (Asian tiger mosquito); adult female, inserting mouthparts to feed on a human host. Copyright Public Domain/released by Centers for Disease Control - original image by James Gathany.	Female Aedes mosquito	Aedes albopictus (Asian tiger mosquito); adult female, inserting mouthparts to feed on a human host.	Public Domain/released by Centers for Disease Control - original image by James Gathany.
Title Female Caption Aedes albopictus (Asian tiger mosquito); close-up of an adult female, inserting mouthparts to feed on a human host. Copyright Public Domain/released by Centers for Disease Control - original image by James Gathany.	Female	Aedes albopictus (Asian tiger mosquito); close-up of an adult female, inserting mouthparts to feed on a human host.	Public Domain/released by Centers for Disease Control - original image by James Gathany.
Title Female Caption Aedes albopictus (Asian tiger mosquito); adult female, feeding on a human host. Note the hugely distended abdomen, indicating that she is almost fully engorged. Copyright Public Domain/released by Centers for Disease Control - original image by James Gathany.	Female	Aedes albopictus (Asian tiger mosquito); adult female, feeding on a human host. Note the hugely distended abdomen, indicating that she is almost fully engorged.	Public Domain/released by Centers for Disease Control - original image by James Gathany.
Title Mated pair Caption Aedes albopictus (Asian tiger mosquito); a pair of mosquitoes during their mating ritual, while the partially engorged female continues to feed on her human host. Copyright Public Domain/released by Centers for Disease Control - original image by James Gathany.	Mated pair	Aedes albopictus (Asian tiger mosquito); a pair of mosquitoes during their mating ritual, while the partially engorged female continues to feed on her human host.	Public Domain/released by Centers for Disease Control - original image by James Gathany.

Identity

Preferred Scientific Name

• West Nile virus Heinz et al., 2000

Other Scientific Names

• West Nile-like virus

International Common Names

• English: WN virus

English acronym

• WNLV
• WNV

Taxonomic Tree

• Domain: Virus
•     Unknown: "Positive sense ssRNA viruses"
•         Unknown: "RNA viruses"
•             Order: Nidovirales
•                 Family: Flaviviridae
•                     Genus: Flavivirus
•                         Species: West Nile virus

Diseases Table

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Pathogen Characteristics

WNV virions are approximately 40 nm in diameter, spherical and contain a lipid envelope. The positive-sense single stranded RNA genome is 11.3 kb in size and contains three structural and seven non-structural proteins. The structural proteins comprise a capsid protein (C), the major envelope protein (E) and either a prM (immature virion) or M (mature virion). WNV is stable at an alkaline pH of 8.0 but is readily inactivated by acidic pH, temperatures above 40°C, organic solvents, detergents, UV-light and gamma-irradiation.

Two genetic lineages have been described (Berthet et al., 1997). Lineage 1 includes isolates from Europe, the Middle East, Africa, India, Australia (KUNV) and from North America (Lanciotti et al., 1999). Lineage 2 includes isolates from West, Central and East Africa and Madagascar which have not been associated with disease outbreaks. Scherret et al. (2001) suggested on the basis of genetic and antigenic analyses that WN viruses should be subdivided into at least 6 subtypes.

The close antigenic relationship of WNV to other flaviviruses is demonstrated in binding assays such as ELISA and haemagglutination-inhibition (HI) using polyclonal and monoclonal antibodies. Neutralising assays are more discriminating, with the envelope glycoprotein E the main target for neutralising antibody. The E protein is also responsible for inducing protective immunity.

Host Animals

Vectors and Intermediate Hosts

References

Berthet FX; Zeller HG; Drouet MT; Rauzier J; Digoutte JP; Deubel V, 1997. Extensive nucleotide changes and deletions within the envelope glycoprotein gene of Euro-African West Nile viruses. Journal of General Virology, 78(9):2293-2297; 22 ref.

Lanciotti RS; Roehrig JT; Deubel V; Smith J; Parker M; Steele K; Crise B; Volpe KE; Crabtree MB; Schereet JH, 1999. Origin of the West Nile virus responsible for an outbreak of encephalitis in the northeastern United States. Science, 286(5448):2333-2337.

OIE, 2003. West Nile fever in Oman. Disease Information, 16(48).

OIE, 2004. West Nile fever in Belize in october 2003. Disease Information, 17(10).

OIE, 2005. West Nile fever in Cuba. Virus detection in equids. Disease Information, 18(7).

Scherret JH; Poidinger M; Mackenzie JS; Broom AK; Deubel V; Lipkin WI; Briese T; Gould EA; Hall RA, 2001. The relationships between West Nile and Kunjin Viruses. Emerging Infectious Diseases, 7(4):697-705.

Distribution Maps