West Nile Virus

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Signs and Symptoms

About 80% of those infected with West Nile Virus will have no symptoms. About 20% will experience mild to moderate flu-like symptoms such as:

  • Fever
  • Nausea, vomiting
  • Headaches
  • Body aches
  • Skin rashes
  • Swollen lymph nodes

These symptoms typically last for only a few days and have no long-term health impact.

Less than 1% (about 1 in 150) of those infected will develop more serious disease, in which there is brain involvement. This can lead to life-threatening encephalitis and/or meningitis. Symptoms of encephalitis include:

  • High fever
  • Extreme muscle weakness
  • Neck stiffness
  • Stupor, disorientation
  • Tremors, convulsions
  • Coma
  • Paralysis (rarely)

The fatality rate of those with the more serious form of the disease ranges from 3-15% and is highest among the elderly. Individuals with compromised immune systems also have an increased risk of severe disease.

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