You can get West Nile virus (WNV) if you are bitten by a mosquito carrying the infection. The mosquitoes become infected when they bite infected birds.
Mosquitoes that carry WNV are most active at dusk and dawn, although they may also bite during the day. Read more about preventing mosquito bites.
Rarely, WNV can also be spread through:
However, only a small number of cases have occurred in these ways.
WNV cannot be spread from close person to person contact - for example, by kissing someone who is infected.
WNV is found in:
Outbreaks of WNV have also occurred in the following European countries:
In 1999, the virus appeared in New York. It has since spread rapidly throughout North America and more recently to:
In tropical countries, it is possible to catch WNV all year round. In countries with changing summer and winter seasons, such as North America, WNV is usually more common during summer and autumn.
West Nile virus (WNV) is a virus spread by mosquitoes.
It is part of the flaviviridae family of viruses which also includes:
Most cases of WNV are not serious and many people have no symptoms or mild flu-like symptoms, such as muscle aches and a fever.
Serious symptoms occur in less than 1 in 100 people infected with the virus and include inflammation of the:
Read more about the general and severe symptoms of West Nile virus.
WNV is usually spread through bites of infected mosquitoes. Mosquitoes become infected when they feed on infected birds. They can then spread the virus to humans and other animals they bite.
In rare cases, WNV can be spread through an organ transplant or blood transfusion. The virus can also be passed from a mother to her baby during pregnancy or through breast milk, although this is also rare.
WNV is found in:
Read more about the causes of West Nile virus.
There is no specific treatment for WNV. If your symptoms are mild, they will usually get better without treatment after a few days or weeks.
If your symptoms are more severe, you will need to go to hospital. You may be admitted and given supportive treatments, such as intravenous fluids (given through a drip in your arm), help with breathing and nursing care.
WNV can be fatal if it becomes severe. It is estimated that around 3-15 people in every 100 die. It is more likely to be fatal in elderly people.
As there is no specific treatment for WNV, it's best to protect yourself from being bitten by mosquitoes when visiting affected areas. The mosquitoes that carry WNV are most active around dusk and dawn.
To avoid being bitten by mosquitoes you should:
Read more about preventing WNV.
There is no specific treatment for West Nile virus (WNV).
If you have mild WNV, your symptoms will usually get better without treatment after several days or weeks.
If your symptoms are more severe, you will need to go to hospital. You may be admitted and given supportive treatments such as:
If your symptoms develop into encephalitis (inflammation of the brain) or meningitis (inflammation of the membranes surrounding the brain and spinal cord), the outlook is less good. These conditions can lead to brain damage and, in some cases, may be fatal.
In around 4 out of 5 people, West Nile virus (WNV) does not cause any symptoms.
In some people, the virus causes mild flu-like symptoms which may include:
These symptoms usually appear 3-15 days after you have been bitten by an infected mosquito, and can last for several days or weeks.
In less than 1 in 100 infected people, WNV can cause a more serious infection of the brain and nervous system, which may take the form of:
People over 50 years of age have an increased risk of developing serious symptoms of WNV if they become infected.
If you have symptoms of West Nile virus (WNV) while travelling, contact a doctor, local hospital or health worker as soon as possible, particularly if your symptoms are severe.
If you are travelling in a remote area, move to a more built up area as soon as possible, where you are more likely to find a doctor and medical care.
If a doctor suspects WNV, they will ask about your medical history. For example, they may ask:
A sample of your blood may be tested for antibodies. Antibodies are special proteins produced by the immune system (the body’s natural defence) to fight infections. If antibodies are found in your blood, you may have further tests to confirm the results.
If your symptoms are severe, you may need a lumbar puncture (also known as a spinal tap). This is a procedure to take a sample of cerebrospinal fluid (CSF), which surrounds your brain and spinal cord.
The fluid will be checked for antibodies and signs of infection, and can also be used to diagnose meningitis (inflammation of the membranes that surround the brain and spinal cord).
In some cases, imaging scans of your head may be taken to rule out other conditions, such as meningitis or encephalitis (brain inflammation) caused by the herpes simplex virus. Possible imaging scans include:
If you are travelling to areas where West Nile virus (WNV) is present, you should be aware of the risks and take appropriate precautions.
Make sure you are aware of potential risks, particularly if you are over 50 years of age, and take steps to protect yourself against mosquito bites.
There is no vaccine for WNV, although scientists are currently working on developing one.
Before travelling, take out adequate travel insurance for countries you will be visiting. Check your insurance policy gives information about what to do if you become seriously ill, and that it covers you for repatriation on medical grounds.
You will need to ensure you are protected from biting mosquitoes at all times as there is no treatment for WNV.
If the virus is reported to be in or near the area where you are travelling, be particularly careful and pay close attention to local news about the movement of the virus.
You should follow the advice listed below while you are away.
Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.