Culex pipiens
Culex pipiens
Culex tarsalis
Culex tarsalis
Culex quinquefasciatus
Culex quinque-fasciatus

Mosquitoes that Carry It

West Nile Virus is carried by Culex pipiens, Culex tarsalis, and Culex quinquefasciatus mosquitoes.

When and Where They Bite

These mosquitoes bite people because they are available. Aedes actually prefer people and seek them out even when other mammals are available. 

Where They Are Most Often Found

West Nile virus is found in all "lower" 48 states.


West Nile Virus incidence map


CDC Morbidity and Mortality Weekly Report West Nile Virus and Other Domestic Nationally Notifiable Arboviral Diseases - United States, 2018. Aug 9, 2019 West Nile virus (WNV) is the leading cause of domestically acquired arboviral disease in the US. Other arboviruses, including eastern equine encephalitis, Jamestown Canyon, La Crosse, Powassan, and St. Louis encephalitis viruses, cause sporadic cases of disease and occasional outbreaks. In 2018, there were 2,813 reported cases of domestic arboviral disease, of which 94% were WNV More than1,650 (63%) were classified as neuroinvasive disease (e.g., meningitis, encephalitis, and acute flaccid paralysis), for a national incidence of 0.51 cases of WNV neuroinvasive disease per 100,000 population. …Arboviral diseases continue to cause serious illness and have no definitive treatment….

CDC Emerging Infectious Diseases Cumulative Incidence of West Nile Virus Infection, Continental United States, 1999–2016 Feb 2019 7 million persons in the United States have been infected with West Nile virus since its introduction in 1999.

Rosenberg, R. et al.  Vital Signs: Trends in Reported Vectorborne Disease Cases—US and Territories 2004-2016 MMWR May 4 2018 Vol 67: 17 pp 496-500. Epidemics characterize the mosquito-borne viruses….Although Lyme disease accounts for 82% of all reported tickborne diseases, spotted fevers, babesiosis and anaplasmosis/ehrlichiosis have become increasingly prevalent.  Dengue, Zika, and chikungunya …can result in explosive epidemics.

CDC Emerging Infectious Diseases Acute and Delayed Deaths after West Nile Virus Infection, Texas, USA, 2002–2012 Feb, 2019 Infection with West Nile virus (WNV) has a well-characterized acute disease process. However, long-term consequences are less understood. We provide population-level evidence of increased risk for death after WNV infection resulting in WNND.

Herring, R. et al.  Pediatric Neurology Pediatric West Nile Virus-Associated Neuroinvasive Disease: A Review of the Literature  March, 2019—West Nile virus-associated neuroinvasive disease, especially in pediatric populations-- epidemiology, clinical, laboratory, and radiographic findings.

Centers for Disease Control and Prevention (CDC) Jan 8, 2019 WNV is now well established in the lower 48 states of the US.  Vector mosquitoes are relatively abundant. Human cases can be expected every year. Avoidance of mosquito bites is the only practical preventive measure available. [This site has a map showing WNV human cases from 2003 to 2018.]

Hernandez, E. et al. Vector Borne and Zoonotic Diseases Environmental and Sociological Factors Associated with the Incidence of West Nile Virus Cases in the Northern San Joaquin Valley of California, 2011-2015. June 18, 2019 Source reduction of mosquito breeding sites and targeted prevention and education remain key in reducing the risk associated with WNV.

Tisoncik-Go, J. et al. Trends in Neurosciences Microglia in Memory Decline from Zika Virus and West Nile Virus Infection. Sep 5, 2019 A recent study by Garber et al. showed that [there may be] cognitive decline during recovery from Zika virus (ZIKV) or West Nile virus (WNV) infection.