West Nile virus (WNV) is an infection that is most commonly spread by being bitten by an infected mosquito. In rare cases, WNV can lead to serious complications and even death. This infection is found worldwide and may occur during late summer and early fall in the United States.
The most common cause is being bitten by a mosquito that is infected with WNV. There are other, rarer causes, such having a blood transfusion with infected blood.
The greatest risk factors for WNV are spending time in areas where mosquitoes are present and not using insect repellent.
Risk factors for having complications from WNV include:
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Most people with WNV have no symptoms. About 20% of the people who become infected with WNV develop flu-like symptoms, for example:
Symptoms may appear within 2-15 days and can last from a few days to several weeks.
A small percentage of people with WNV will develop serious, neurological symptoms that affect the brain and spinal cord. These symptoms may include:
These serious symptoms can lead to death.
In addition to taking your medical history and doing a physical exam, your doctor will ask you:
A blood test is commonly used to confirm the diagnosis of WNV. Depending on the symptoms that you have, your doctor may order other tests, such as:
Treatment for WNV focuses on supportive care. Depending on your symptoms your doctor may recommend:
If you are dehydrated, you may need to drink an oral rehydration solution or have fluid delivered intravenously through a vein in your arm.
Treatment for severe symptoms may include:
The best preventive measure is to avoid mosquito bites. You can do this by:
Mosquitoes contract WNV by biting infected birds. If you see a dead bird, call the public health department. Do not touch the dead bird unless you are wearing disposable gloves.
Last reviewed September 2012 by Michael Woods, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.