About West Nile Virus
- West Nile Encephalitis Fact Sheet
Answers to frequently asked questions about West Nile encephalitis.
- West Nile is one of several mosquitoborne diseases that have been seen in Minnesota.
- 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
- sore throat
- 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
- 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.
- CDC: West Nile Virus: What You Need To Know