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West Nile Virus

West Nile virus (WNV) is a disease also known as a Flavivirus (other Flaviviruses include Zika virus and dengue virus) that first appeared in the United States in 1999. In Alabama, WNV cases have been reported from every public health district.

The West Nile virus is cycled between birds, mosquitoes, mammals, and humans with infected mosquitoes as the vector of the disease. This means that a mosquito becomes infected when it bites an infected bird. Once a mosquito is infected, it can spread the virus to humans and horses. The Culex pipiens group of mosquitoes is the most common species associated with vectoring WNV to both humans and horses. WNV is not spread by the following:

  • Coughing or sneezing
  • Human-to-human touching
  • Touching live animals or dead infected birds
  • Eating infected birds or animals

About West Nile Virus Infection

  • Most commonly (8 in 10 people infected with WNV) are asymptomatic (develop no symptoms). Some people infected (1 in 5 infected) develop a fever and mild or moderate flu-like illness (symptoms include: headache, body aches, joint pains, vomiting, diarrhea, or rash). Most people with this type of WNV fully recover.
  • Serious and severe symptoms are less common (1 in 150 people infected with WNV) affecting the central nervous system (encephalitis or meningitis). Further symptoms include: high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. People of any age can be infected by WNV, though people over 60 years of age or are immunocompromised are at a greater risk of infection.
  • Typically people develop symptoms 3 to 14 days after they have been bitten by an infected mosquito.
  • In extremely rare cases WNV has been spread by a laboratory exposure, blood transfusion/organ donation, and from mother to baby (i.e., pregnancy, delivery, or breast feeding).


  • There is no vaccine for treatment of WNV.
  • There are no specific antiviral treatments for WNV.
  • Over-the-counter pain relievers can be used to treat symptoms.
  • Severe cases often require hospitalization for supportive treatment.
  • If you or a family member develop the symptoms of WNV contact your healthcare provider.

Detect, Test, and Report

The best way to protect yourself from WNV and other insect-borne illness is to prevent exposure to insect bites. For more information about preventing exposure to mosquito-borne disease: Avoid the Bite

Using air conditioning or window and door screens reduces the risk of mosquitoes coming indoors. Proper application of mosquito repellents on exposed skin and proper clothing decreases the risk of being bitten by mosquitoes. For more information on how to control mosquitoes around your home Vector Control. To learn more about insect repellents, visit this Environmental Protection Agency website: Insect Repellent Information from the EPA

ADPH displays case counts on the Mosquito-borne Diseases page and on the Annual Reports, and submits it to CDC's ArboNET. Case counts are updated weekly.

For the General Public

For Healthcare Professionals

For Veterinarians

For questions or concerns regarding insect-borne disease in Alabama, see the Contact Us page, or email us at [email protected].

Page last updated: June 26, 2024