Symptoms of West Nile virus

Learn about the symptoms of West Nile virus, what to look for and what to do if you become ill.

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What are the symptoms of West Nile virus?

Symptoms can range from mild to severe. Most people (70% to 80%) who are infected with West Nile virus have no symptoms.

Some people have mild symptoms that can include:

  • fever
  • headache
  • body aches
  • mild rash
  • swollen lymph glands

First symptoms usually appear within 2 to 15 days after infection.

Anyone infected with West Nile virus can be at risk of developing more severe symptoms and health effects. Adults 50 years or older and those with underlying conditions or weaker immune systems, however, are at greater risk.

Very few people (fewer than 1 per cent of people infected with the virus) will develop severe symptoms and health effects. In many of these cases, the infection can affect the central nervous system. This is the nervous system tissues in the brain and spinal cord).

Serious symptoms can include:

  • rapid onset of severe headache
  • high fever
  • stiff neck
  • nausea or vomiting (sometimes both)
  • difficulty swallowing
  • drowsiness
  • confusion

You can also get serious symptoms like:

  • loss of consciousness
  • lack of coordination
  • muscle weakness
  • paralysis

In general, recovery can take a week for mild cases. Some severe cases could experience a variety of health effects for many months to years after their initial illness. Some severe cases of the disease can be fatal.

What do you do if you become ill?

See your health care provider immediately if you develop symptoms of West Nile virus after getting a mosquito bite.

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