10939 West Nile Virus
Informed by recognized medical guidance
Overview
West Nile virus is an infection spread by mosquito bites. Most people who get it never feel sick. Some have mild flu-like symptoms, and rarely, it can cause serious illness affecting the brain.
Key facts
- West Nile virus is spread by mosquito bites, not from person to person.
- Most infections are mild — around 4 in 5 people show no symptoms at all.
- Severe illness is rare but can be serious, especially for older adults and people with weak immune systems.
It is not common in most parts of the UK. Outbreaks happen in other countries, especially in summer and early autumn, and mainly in areas where the virus is known to circulate.
Anyone can catch West Nile virus if bitten by an infected mosquito. But you are more likely to get seriously ill if you are over 50, have a long-term health condition, or have a weakened immune system.
Symptoms
- Sudden severe headache
- Stiff neck and high fever
- Sudden confusion or difficulty speaking
- Seizures or convulsions
- Muscle weakness, especially on one side of the body
- Difficulty waking or staying awake
- Paralysis or loss of movement
- ⚠Fever lasting more than a few days that is getting worse
- ⚠Severe headache that is not helped by usual pain relief
- ⚠New rash with fever and tiredness
- ⚠Feeling very drowsy or confused sometimes
- ⚠Any unusual weakness or shaking
Common symptoms
- Fever
- Headache
- Body aches and joint pain
- Feeling very tired
- Skin rash (usually on the chest, back, or arms)
- Swollen lymph nodes (small lumps under the skin)
Symptoms in children
- Fever
- Fussiness or crying more than usual
- Tiredness or drowsiness
- Headache
- Loss of appetite
Symptoms in older adults
- High fever
- Stiff neck
- Confusion or disorientation
- Muscle weakness or twitching
- Sensitivity to light
Causes
Main causes
- West Nile virus is spread through the bite of an infected mosquito. Mosquitoes pick up the virus when they feed on infected birds. The virus then can pass to people when the mosquito later bites them.
- The virus is not caught by casual contact, like touching or coughing. It also cannot be passed through food, water, or normal day-to-day activities.
Risk factors
- Living or travelling to areas where West Nile virus is active
- Being outdoors a lot, especially at dawn and dusk when mosquitoes are most active
- Not using mosquito repellent or protective clothing
- Older age — the risk of severe illness increases after 50
- Having diabetes, high blood pressure, or a weakened immune system
When to see a doctor
See a doctor urgently if:
- Go to urgent care (same day) if you have a fever with a severe headache, stiff neck, confusion, or unusual weakness.
- See a doctor within 24 hours if you have a fever and a new rash, or if you feel very unwell and are getting worse.
Book a routine appointment if:
- Make a routine appointment with your GP if you have been bitten by a mosquito and have a mild fever, headache, or tiredness lasting more than a few days.
- Ask for a check-up if you have been in an area where West Nile virus is possible and you feel unwell, even if symptoms are mild.
Diagnosis
A doctor will ask about your symptoms, travel history, and possible mosquito bites. If they suspect West Nile virus, they may recommend a blood test to look for antibodies your body has made against the virus.
Tests that may be done
- Blood test to check for West Nile virus antibodies
- In some cases, a lumbar puncture (a needle to take a small amount of fluid from around the spine) if there are signs of brain or nervous system involvement
What to expect at your appointment
You may need to wait a few days for test results. If your symptoms are mild, the doctor may not order tests and will instead ask you to rest and monitor your symptoms.
Treatment
There is no specific medicine that cures West Nile virus. Treatment focuses on relieving symptoms and supporting the body while it fights off the infection. Most people with mild symptoms can recover at home.
Self-care at home
- Get plenty of rest and sleep
- Drink enough fluids to stay hydrated
- Use over-the-counter medicines to reduce fever and pain (ask your pharmacist for advice)
- Keep an eye on symptoms and contact a doctor if they get worse
Medical treatments
For severe illness, treatment is given in hospital. It may include fluids through a drip, breathing support, and therapies to help with symptoms such as seizures or muscle weakness. There is no specific medicine for West Nile virus.
When is surgery considered?
Surgery is not used to treat West Nile virus.
Living with this condition
If you have had a mild infection, you can usually return to normal activities once your fever has gone and you feel better. People with severe illness may need weeks or months to recover, and at first may need help with daily tasks.
Lifestyle tips
- Take it easy — your body needs time to recover
- Get gradual return to exercise only when you feel ready
- Continue using mosquito repellent to avoid further bites while you recover
- Keep in touch with your healthcare team if you are recovering from a severe infection
Diet and exercise
Eating a balanced diet with plenty of fruit, vegetables, and protein can support your recovery. Start with light activities like walking, and gradually increase as you feel stronger. If you had severe illness, speak to a physiotherapist about a safe exercise plan.
Mental health and emotional wellbeing
Some people feel anxious or low after being ill, especially if recovery takes a long time. It is normal to be worried about your health. Talk to your doctor if you are struggling, and consider reaching out to a friend or counsellor for support.
Prevention
Yes, the best way to prevent West Nile virus is to avoid mosquito bites, especially when travelling to areas where the virus is found. There is no human vaccine for West Nile virus.
Vaccines
There is currently no vaccine available for West Nile virus for humans. The most effective protection is preventing mosquito bites.
Screening programmes
There is no routine screening test for West Nile virus. Testing is done only when someone has symptoms that suggest the infection.
Complications
If left untreated
- Severe West Nile virus can cause inflammation of the brain (encephalitis) or the lining of the brain (meningitis).
- It can also lead to long-term neurological problems such as memory issues, tremors, or muscle weakness.
- Very rarely, it can be fatal, especially in older adults or people with weak immune systems.
Long-term outlook
Most people who catch West Nile virus recover completely and have no lasting problems. Even among those who get severe symptoms, many improve with hospital care, although recovery can be slow. Staying aware of symptoms and seeking medical advice early gives you the best chance of a good outcome.
Find support
International organisations
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Always verify with your doctor
Health guidelines vary by country and region. The information in this article is based on international clinical guidelines but may not reflect the specific guidelines, medications, or practices in your country. Always discuss your health concerns with your own doctor or healthcare provider, and refer to your local national health guidelines where available.
Important notice This information is for educational purposes only. It does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider about your specific situation. If you are experiencing a medical emergency, call your local emergency services immediately.
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Sources and guidance
This article is educational and is prepared with reference to recognized health information and clinical guidance sources where available. Specific source links may vary by topic.
Last updated: July 31, 2026
Educational note: This information is for education only and is not a diagnosis.
Use it to support, not replace, advice from a licensed clinician.
If symptoms are severe, worsening, or urgent, call your local emergency number or seek emergency care.