West Nile virus: West Nile is a virus that is spread by mosquito bites. Most people infected with West Nile virus do not have symptoms. About 1 in 5 people develop symptoms such as fever, rash, and muscle aches. Rarely, West Nile can cause serious brain and spinal cord inflammation (encephalitis and meningitis).
Symptoms of West Nile virus include fever, headache, muscle pain, nausea, vomiting, diarrhea, rashes, etc. In most cases, West Nile virus symptoms are flu-like. Less than 1% of people develop severe symptoms involving the nervous system.
What is West Nile virus?
West Nile is a virus that is spread by mosquito bites. Most people who are infected do not develop symptoms. However, about 1 in 5 people develop fever, headache, body aches, and other flu-like symptoms (sometimes called West Nile fever). Rarely, West Nile virus infects your nervous system and causes serious inflammation (encephalitis or meningitis) of the brain or spinal cord.
West Nile virus is named after the West Nile district of Uganda, where it was first identified.
How common is West Nile virus?
West Nile virus is found in many parts of the world, including North America, Europe, Africa, the Middle East, Australia, and Asia. It is the most common mosquito-borne virus in the United States, with cases reported in 49 states. More than 51,000 symptomatic cases have been reported in the United States since the first cases in the country in 1999.
Symptoms and causes
What are the symptoms of West Nile virus?
Symptoms of West Nile fever include:
- Fever.
- Headache.
- Muscle aches.
- Nausea and vomiting.
- Diarrhea.
- Rash (usually concentrated around your chest and back).
- Swollen lymph nodes.
- Sore throat.
- Pain behind your eyes.
West Nile encephalitis and meningitis
Symptoms of more severe West Nile infections include:
- Severe, very painful headache.
- High fever (over 103 degrees Fahrenheit or 39.5 degrees Celsius).
- Stiff neck. You can’t move your chin toward your chest.
- Confusion.
- Muscle weakness.Muscle movements that you can’t control (tremors or spasms).
- Seizures.
- Paralysis.
- Coma.
What causes West Nile virus?
West Nile is an arbovirus or a virus you get from arthropods (arthropods are a large group that includes insects). It’s an RNA virus of the flavivirus genus. Similar viruses cause dengue fever, yellow fever, and Zika.
How is West Nile virus spread?
Infected mosquitoes spread West Nile virus. They usually get the virus by biting an infected bird (there’s no evidence that humans get it directly from birds). The virus grows inside the mosquito, and it infects you (or another animal) when it bites you. The incubation period — how long it takes for you to show symptoms — is usually two to six days after the bite (but can be up to 14 days).
In very rare cases, West Nile virus is spread:
- From a pregnant woman to her unborn baby.
- Through human milk.
- Through blood transfusions.
- Through organ transplants.
How contagious is West Nile virus?
West Nile is not contagious. You cannot get it from someone who has the disease.
What are the risk factors for West Nile fever?
Mosquitoes can bite anyone. But some people have a higher risk of getting seriously ill from West Nile. You may be at higher risk if you:
- Are over age 60.
- Are you an organ transplant recipient?
- Have cancer.
- Have diabetes.
- Have high blood pressure (hypertension).
- Have kidney disease.
What are the complications of West Nile virus?
Less than 1% (about 1 in 150) of people infected with West Nile will have serious symptoms. The most common complication is inflammation of part of your nervous system (your brain and spinal cord), including encephalitis and meningitis.
Long-term effects of a severe West Nile infection can include:
- Memory loss.
- Deafness.
- Difficulty walking or gait disorders.
- Muscle weakness.
- Abnormal reflexes.
- Depression.
Diagnosis and Testing
How is West Nile virus diagnosed?
A provider may test your blood or cerebrospinal fluid (CSF) to check for antibodies or other signs of West Nile virus infection. They usually do these tests only if you’re seriously ill. If you have signs of brain swelling, they’ll obtain images of your brain with a CT scan (computed tomography scan) or MRI (magnetic resonance imaging).
Management and treatment
How is West Nile virus treated?
There is no antiviral medication that cures West Nile virus. You can treat mild symptoms at home with over-the-counter (OTC) medications like you would take for a cold or flu.
If you have severe neurological symptoms, providers will monitor you in the hospital. They may treat your symptoms or try to reduce brain swelling by:
- Antiseizure medications if you’re having seizures.
- Supplemental oxygen or mechanical ventilation to help you breathe.
- Intravenous (IV) fluids to keep you hydrated.
- Corticosteroids to reduce swelling.
- Feeding by tube (if you can’t feed yourself).
Prevention
Can you prevent West Nile virus?
There is no vaccine to prevent West Nile virus. The best way to reduce your risk is to protect yourself from mosquito bites. Here are ways to do this:
- Avoid high-risk times: Stay indoors when mosquitoes are most active, especially during the early morning and at sunset.
- Use insect repellent: Spray insect repellent on exposed skin or clothing before going outside. Check for products registered by the Environmental Protection Agency (EPA) for effectiveness.
- Cover your skin: Wear lightweight clothing, such as long pants or long-sleeved shirts, to cover more of your body when you’re outside.
- Remove standing water: Regularly empty and clean all areas where water can collect, such as birdbaths or clogged rain gutters, where mosquitoes can breed.
- Keep mosquitoes out of the house: Keep doors and windows closed or locked to prevent mosquitoes from entering the house.
- Take precautions when travelling or sleeping outside: Sleep with the windows closed as much as possible, or use a mosquito net to avoid mosquito bites at night.
Outlook/Prognosis
Can you ever get rid of West Nile virus?
Yes, in most people, their immune system eventually fights off West Nile virus. The flu-like symptoms usually clear up on their own. But if your immune system is weakened, it may be difficult to get rid of the viral infection. Nervous system damage from a severe West Nile infection can be permanent, even after the virus is gone.
How long does West Nile virus survive?
Mild symptoms of West Nile usually resolve completely within a few weeks. Sometimes, fatigue and muscle weakness can last for months. After a nervous system infection, you may have long-term or permanent memory loss, hearing loss, balance or gait problems, and other neurological problems.
Is West Nile virus fatal?
West Nile is fatal for about 1 in 10 people with nervous system infection (or 1 in 1,500 people with West Nile).
Living with it
When should I see my healthcare provider?
If you think you may have West Nile virus, talk to a healthcare provider. They can tell you:
- Do you need testing?
- What signs of serious illness to look for?
- How to take care of yourself at home?
- When to contact them.
When should I go to the emergency room?
Go to the emergency room if you have symptoms of serious illness, including:
- Severe headache.
- High fever.
- Stiff neck.
- Confusion.
- Muscle weakness or tremors.
- Seizures.
What questions should I ask my doctor?
It may be helpful to ask your healthcare provider:
- When can I expect to feel better?
- How do I manage my symptoms at home?
- What serious symptoms should I look out for?
- When should I contact you?
A note from the Cleveland Clinic
Most of the time, mosquitoes are just an unpleasant nuisance. But sometimes they carry viruses that can make you sick. Fortunately, 80% of people who get West Nile never develop symptoms. And most people have a very low risk of getting seriously ill.
If you live around mosquitoes, you can take steps to protect yourself from their bites. If you do get bitten by a mosquito, see a healthcare provider if you have symptoms of West Nile. They can help you understand what serious symptoms to look for and answer any questions you have.
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conclusion
While West Nile virus is primarily spread through mosquito bites and often results in mild, flu-like symptoms, it can occasionally lead to severe complications affecting the nervous system. Understanding the symptoms and causes of West Nile virus is crucial for early detection and treatment. Prevention remains the best defense, so taking steps to avoid mosquito bites and reducing mosquito breeding sites around your home can significantly lower your risk. If you experience any severe symptoms, it’s important to seek medical attention promptly. Stay informed, take precautions, and consult with healthcare providers to manage and prevent West Nile virus effectively.
