West Nile Virus Portal


West Nile Virus (WNV) Classification

ICTV Group: Unassigned
Baltimore Group: Group IV [(+) ssRNA, no DNA stage]
Family: Flaviviridae
Genus: Flavivirus
Species: West Nile virus (WNV)


West Nile virus (WNV) is mosquito-borne RNA virus of the flaviviridae family that includes other human pathogens such as the dengue virus, yellow fever virus and Japanese encephalitis virus. WNV perpetuates in nature in a seasonal cycle between mosquitoes (mainly Culex sp.) and birds.  Since its introduction into North America in 1999, WNV has caused annual seasonal epidemics, leading to several thousand cases of human disease, symptoms of which range from mild febrile illness to fatal encephalitis. Prior to 1999, WNV was distributed in Africa, Asia and Australia, with sporadic epidemics of human disease occurring in Europe and Asia following the introduction of the virus via migrating birds. The virus has subsequently spread throughout much of North and South America. WNV is a classic example of an introduced, emerging infectious disease that has rapidly developed into a significant public health burden.  

Image Captions and Credits

The images on this page are, from left to right:

  1. Photo of Culex quinquefasciatis from the CDC's Public Health Image Library; photographer: Jim Gathany.
  2. Transmission electron micrograph (TEM) of the West Nile virus (WNV) from the Wellcome Photo Library, Wellcome Images.
  3. Transmission electron micrograph (TEM) of the West Nile virus (WNV) from the CDC's Public Health Image Library; photographer: Cynthia Goldsmith.
  4. A surface-shaded image of the West Nile virus particle produced by Purdue University biologists using cryoelectron microscopy, from Purdue Department of Biological Sciences.
  5. This image shows the orientation of the envelope protein molecules that compose the surface of a West Nile virus particle. The major surface protein is composed of three domains color-coded pink, yellow and blue. The proteins self-assemble in a host cell, forming a well-organized geometric shape. Knowledge of the proteins' structure could help scientists in the effort to develop antiviral agents. From Purdue Department of Biological Sciences.

Funding Information

This sequencing project was supported by the National Institute of Allergy and Infectious Disease, National Institutes of Health funded Genome Sequencing Center for Infectious Diseases at the Broad Institute.