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West Nile Virus

Scientific Name

Orthoflavivirus nilense (ICTV 2023)

Common Name

West Nile Virus (WNV)

Native To

First discovered in Africa (Roehrig 2013)

Date of U.S. Introduction

1999 (Roehrig 2013)

Means of Introduction

Unknown (Roehrig 2013)


Infects birds and mammals (including humans). West Nile virus is primarily an avian pathogen, and is transmitted among birds by ornithophilic (bird-biting) mosquitoes; including the Asian tiger mosquito and other mosquito species (Hayes et al. 2005)

Current U.S. Distribution

Most of U.S.

West nile virus - DOI, USGS
Image use policy

USGS Wildlife Veterinarian testing for the West Nile Virus USGS, National Wildlife Health Center DOI. USGS. Newsroom.

Find more images

Distribution / Maps / Survey Status

  • ArboNET Disease Maps

    • DHHS. Centers for Disease Control and Prevention.

    • Maps updated to present. Select data by disease (WN), vector (mosquito), state, and year (includes historical data from 2003).

  • West Nile Virus - Data & Maps

    • DHHS. Centers for Disease Control and Prevention.

    • Includes final annual and cumulative maps and data from 1999.


Selected Resources

The section below contains highly relevant resources for this species, organized by source.

Federal Government
State and Local Government