ARC West Nile Virus FAQs

What is West Nile virus?

West Nile virus (WNV) is a virus carried by mosquitoes. Of those infected by the virus, 80% will have no symptoms. There is only one form of the seasonal virus, but two forms of the illness:

  • WNV fever: 20% of those infected have mild symptoms
  • WNV neuroinvasive disease: Only a few develop serious symptoms

What are the symptoms?

About 4 out of 5 infected people don’t have symptoms. Children are more likely to have symptoms than adults. When symptoms do occur, they are usually mild and last a few days. Symptoms of WNV infection may include:

  • fever
  • headache
  • body aches
  • nausea or vomiting
  • rash
  • swollen lymph glands

More severe infection includes symptoms of tremors, stiff neck, high fever, severe headache, paralysis, muscle weakness, confusion, and convulsions.

People age 50 and older and those with compromised immune systems are at greater risk for severe complications, such as encephalitis and meningitis, both potentially fatal. A WNV infection usually does not involve the brain. However, some people develop WNV neuroinvasive disease, a polio-like syndrome with sudden weakness and paralysis.

How is it diagnosed?

Your healthcare provider will ask about the symptoms, give an examination, and may administer the following tests:

  • Blood tests.
  • Spinal tap (lumbar puncture): a procedure in which a needle is inserted between 2 bones of the spine into the spinal canal to take a sample of spinal fluid to test for meningitis.
  • Diagnostic testing: only recommended for severe cases.

How long will the effects last?

Most people infected with WNV, including nearly all children, don’t get seriously ill, and they recover fully. Symptoms usually last 3 to 6 days, but they can last as long as several weeks or months.

If you have a serious infection, you may be ill for weeks or months. Your nervous system or brain may be injured and the injury is sometimes permanent. If you get WNV, you will probably be immune to future infection by the virus, but your immunity might decrease over time.

How is it treated?

There is no medicine that cures West Nile virus. If the symptoms are mild, they will go away on their own. Most people with mild symptoms can care for themselves at home.

If there is a serious infection, you may need to stay at the hospital to receive intravenous (IV) fluids and pain relievers. For severe or life-threatening infection, you may need treatment in an intensive care unit.

How can I take care of myself?

  • Rest.
  • Take acetaminophen (Tylenol) or an anti-inflammatory medicine such as ibuprofen for fever, headache, or muscle aches. Check with your healthcare provider before you give any medicine that contains aspirin or salicylates to a child or teen. This includes medicines like baby aspirin, some cold medicines, and Pepto- Bismol.
  • Contact your healthcare provider right away if you develop new or worsening symptoms, especially of the nervous system, for example: a stiff neck, severe headache, a fever of 101.5°F (38.6°C) or higher that does not go down with medicine, tremors, seizures (convulsions), slurred speech, confusion, or muscle weakness or paralysis (inability to use an arm or leg).

How can I prevent West Nile virus infection?

WNV can be prevented by taking precautions to avoid exposure to mosquitoes. You can help protect yourself, your family, and pets from WNV by following the “4 D’s”:

  • DEET: Use this type of bug repellent on skin and clothes. Children older than two months can use repellents with no more than 30% DEET.
  • Drain standing water: It only takes a teaspoon of water for mosquitoes to lay their eggs. 
  • Dress: Wear long sleeves and long pants.
  • Dusk & Dawn: Avoid mosquitoes’ most active hours.

And for your household pets, like cats and dogs:

  • Watch for the same symptoms in animals as in people.
  • DON’T use a bug repellent with DEET in it on your pet; use an organic bug repellent for your pets.
  • If your pet starts to slow down or seems more lethargic, especially if they are young, check with your veterinarian.


Developed by Austin Regional Clinic

This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.