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West Nile Virus
A mosquito is shown in this image.

West Nile Virus (WNV) is a viral disease that has emerged in temperate regions of North America and presents a threat to both public and animal health. 

WNV has become established as a seasonal disease that flares up in the summer months and continues into the fall.

Photo by: U.S. Army Sgt. Jonathan W. Thomas

  • WNV seems to be spread most com­monly to humans through the bite of a mosquito that has fed on infected animals.
  • WNV also can be spread through blood transfusions or from mother to child.
  • WNV is not spread through casual contact with people.
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  • Approximately 80% of those in­fected never show any symptoms.
  • Approximately 20% of those infected experience only mild symptoms for a few days:
    • Fever
    • Headache
    • Body aches
    • Nausea  
    • Vomiting
    • Swollen lymph nodes
    • Skin rash
  •  Fewer than 1% of those infected with WNV develops serious symp­toms that may last several weeks:
    • High fever
    • Headache
    • Neck stiffness
    • Stupor
    • Disorienta­tion
    • Coma
    • Tremors
    • Convulsions
    • Muscle weakness
    • Vision loss
    • Numbness
    • Paralysis
    • Permanent neurological damage
  •  If symptoms develop, it is typi­cally between 3 to 14 days after an individual is bitten by an infected mosquito.
  • If you experience any symptoms, contact your physician.
  • No vaccine or specific antiviral treatments for WNV infection are available.
  • Over-the-counter pain relievers can be used to reduce fever and relieve some symptoms.

The best way to avoid WNV is to avoid mosquitoes:

  • Wear insect repellent on any exposed skin when outside.
  • Try to wear long sleeves, pants, and socks—clothing can protect from mosquitoes.
  • Be aware of peak mosquito hours in your area.
  • Drain standing water to prevent mosquitoes from multiplying.
  • Maintain screens on windows and doors to prevent mosquitoes from entering buildings.

Set your own course through any hazard: stay informed, make a plan, build a kit.
Live Ready Marine Corps.

Where to Find Additional Information
Centers for Disease Control and Prevention (CDC)
CDC's West Nile Factsheet
Downloadable PDF