West Nile Virus
DefinitionWest Nile virus (WNV) is an infection that is most commonly spread by a mosquito bite. In rare cases, WNV can lead to serious complications, or death.This infection is found worldwide. In the United States, it tends to occur during late summer and early fall.
CausesWest Nile is caused by a virus. The virus is passed through the bite of an infected mosquito. The virus can also be passed through a blood transfusion with infected blood, but this is rare.
Risk FactorsThe greatest risk factors for WNV are spending time in areas where mosquitoes are present and not using insect repellent. The risk of complications with WNV is highest in people:
- Over 50 years old
- With a weakened immune system
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SymptomsMost people with WNV have no symptoms. About 20% of the people who become infected with WNV develop flu-like symptoms such as:
- Fever and chills
- Muscle pain
- Nausea and vomiting
- Swollen lymph nodes
- Eye inflammation— conjunctivitis
- High fever
- Stiff neck
- Vision loss
- Severe muscle weakness
DiagnosisIn addition to taking your medical history and doing a physical exam, your doctor will ask you:
- What kind of symptoms you are experiencing
- Where you have been living or traveling to
- Whether you have been exposed to mosquitoes
TreatmentTreatment for WNV focuses on supportive care. Depending on your symptoms your doctor may recommend:
- Pain relievers
- Antiemetics to reduce nausea and vomiting
- Breathing support— mechanical ventilation
- Medication to control seizures
- Medication to decrease brain swelling
PreventionThe best preventive measure is to avoid mosquito bites. Prevention steps include:
- Avoid outdoor activities at dawn or dusk.
- Wear long pants and long-sleeve shirts when outdoors.
- Use an insect repellent with DEET.
- Repair screens to prevent mosquitoes from entering the house.
- Use proper mosquito netting at night. Look for netting treated with insecticide.
- Remove standing water to prevent mosquito breeding. Empty items like bird baths and gutters around your house.
Centers for Disease Control and Prevention
National Library of Medicine
West Nile virus infection. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated February 1, 2013. Accessed May 21, 2013.
West Nile virus: What you need to know. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/westnile/index.html. Updated September 12, 2012. Accessed May 21, 2013.
10/1/2013 DynaMed Systematic Literature Surveillance http://www.ebscohost.com/dynamed : Reimer LJ, Thomsen EK, et al. Insecticidal bed nets and filariasis transmission in Papua New Guinea. N Eng J Med. 2013;369(8):745-753.
- Reviewer: David L. Horn, MD, FACP
- Review Date: 12/2014
- Update Date: 12/20/2014