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, and 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 info on how to control mosquitos around your home Vector Control. To learn more about insect repellents, visit this Environmental Protection Agency website: Insect Repellent Information from the EPA
Infectious Diseases & Outbreaks Division, Field Surveillance Staff (FSS), investigate all reports of West Nile disease from notifiable disease reporters. ADPH displays the confirmed cases on the Alabama Morbidity Report, Arbovirals, and submits it to CDC's ArboNet for display by county, see West Nile Alabama Cases links below. Case counts are updated weekly.
For the General Public
- CDC West Nile Virus Homepage
- CDC West Nile Fact Sheet (4 MB)
- CDC Insect Repellent Use and Safety
- Mosquito Myths from the University of Florida Medical Entomology Lab
For Healthcare Professionals
- CDC West Nile Virus Information and Guidance for Clinicians
- CDC West Nile and Blood Transfusion and Organ Donation
- CDC West Nile Statistics and Maps
- CDC Neato Mosquito - An Elementary Curriculum Guide on Mosquito Biology and the Prevention of La Crosse Encephalitis Virus infection
- The Buzz-z-z on West Nile Virus
Page last updated: September 16, 2019