About West Nile Virus

On this page:
Fact Sheet
Transmission
Prevention
Signs and symptoms
More from other websites

Fact Sheet

• West Nile Encephalitis Fact Sheet
  Answers to frequently asked questions about West Nile encephalitis.
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Transmission

• West Nile is one of several mosquitoborne diseases that have been seen in Minnesota.

Prevention

• Preventing Mosquitoborne Diseases
  Learn how to minimize your risk to West Nile and other diseases transmitted by mosquitoes.
  
  
• There is a vaccine available to prevent West Nile encephalitis in horses. Please contact your veterinarian for vaccine recommendations. A human West Nile vaccine is still in development.

Signs and symptoms

The typical incubation period for West Nile is 2-6 days, although it can be as long as 15 days.

• Most people infected with West Nile virus will be asymptomatic or experience a flu-like illness
  
  
• 20% of those bitten by an infected mosquito will develop the symptoms of West Nile fever
  
  
• 1 out of 150 people bitten by an infected mosquito will develop the more severe form of West Nile, West Nile encephalitis
  

West Nile fever

• West Nile fever symptoms include:
  • sudden onset of high fever (usually >102°F)
  • severe headache
  • nausea
  • vomiting
  • sore throat
  • backache
  • joint pain
  • prominent muscle aches and weakness
  • prolonged fatigue
  • rash (more commonly associated with West Nile fever than encephalitis)
  • swollen lymph nodes

West Nile encephalitis

Less than 1% of those infected with West Nile will develop severe neurological symptoms consistent with encephalitis or meningitis.

• West Nile encephalitis symptoms include:
  • mental status changes
  • vomiting
  • sensitivity to light
  • altered reflexes
  • seizures (less frequent)
  • 15% progress to coma
  • Acute flaccid paralysis (AFP) occurs in a small percentage of severely affected patients

The death rate among those showing symptoms of severe West Nile infection (encephalitis or meningitis) is around 10%. Most severe cases occur in elderly people.

More information

• CDC: West Nile Virus: What You Need To Know
  CDC Factsheet.