West nile virus (patient information)
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West nile virus disease |
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West nile virus disease On the Web |
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Risk calculators and risk factors for West nile virus disease |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Priyamvada Singh, M.B.B.S.
Overview
West Nile Virus is an illness spread by mosquitoes. Sometimes, it can cause serious infections of the brain, spinal cord and nerves, but this is rare.
Most people who get West Nile Virus do not get sick. Others may have mild symptoms such as fever, headache, and feeling tired. People are most likely to get West Nile Virus in the late summer and early fall.
What are the symptoms of West nile virus disease?
Most people who are infected with West Nile virus have no symptoms. Others may have only mild symptoms, which is called West Nile fever. Symptoms include:
- Skin rash
- Fever
- Headache
- Nausea
- Vomiting
- Diarrhea
- Loss of appetite
- Swollen lymph nodes (lymph glands)
- An achy feeling in the back and muscles
Symptoms usually occur 3 to 14 days after a person is bitten by an infected mosquito and last for 3 to 6 days. Symptoms of the more severe illness the West Nile virus include:
- A sudden high fever (above 102°F)
- Severe headache
- Stiff neck
- Feeling disorientated or confused
- Tremors or muscle jerks
- Seizures
- Coma
- Weakness or partial paralysis
These symptoms may last for several weeks. Contact your doctor if you have any of these symptoms and have recently been bitten by a mosquito.
In rare cases, West Nile virus causes a disease such as a swelling of the brain called encephalitis (say: en-seff-uh-lie-tuss) or swelling of the membrane around the brain and spinal cord called meningitis (say men-in-ji-tuss). This can lead to permanent brain damage or death.
What causes West nile virus disease?
- West Nile virus was first identified in 1937 in Uganda in eastern Africa. It was first discovered in the United States in the summer of 1999 in New York. Since then, the virus has spread throughout the United States.
- The West Nile virus is a type of virus known as a flavivirus. Researchers believe West Nile virus is spread when a mosquito bites an infected bird and then bites a person.
- Mosquitoes carry the highest amounts of virus in the early fall, which is why the rate of the disease increases in late August to early September. The risk of disease decreases as the weather becomes colder and mosquitoes die off.
- Although many people are bitten by mosquitoes that carry West Nile virus, most do not know they've been exposed. Few people develop severe disease or even notice any symptoms at all.
- West Nile virus may also be spread through blood transfusions and organ transplants. It is possible for an infected mother to spread the virus to her child through breast milk.
Who is at highest risk?
Only a few mosquitoes carry West Nile Virus. For most people, the risk is low. Some people have a higher risk. People who are outside a lot have a greater chance of being bitten. People older than 50 are more likely to get very sick if they get West Nile Virus. People who already have health problems also have a greater risk.
When to seek urgent medical care?
Call your health care provider if you have symptoms of West Nile virus infection, especially if you may have had contact with mosquitoes. If you are severely ill, go to an emergency room.
If you have been bitten by an infected mosquito, there is no treatment to avoid getting West Nile virus infection. People in good general health generally do not develop a serious illness, even if they are bitten by an infected mosquito.
Diagnosis
Signs of West Nile virus infection are similar to those of other viral infections. There may be no specific findings on a physical examination. However, up to half of patients with West Nile virus infection may have a rash.
Tests to diagnose West Nile virus include:
- Complete blood count (CBC)
- Head CT scan
- Head MRI scan
- Lumbar puncture and cerebrospinal fluid (CSF) testing
The most accurate way to diagnose this infection is with a serology test, which checks a blood or CSF sample for antibodies against the virus. More rapid techniques using polymerase chain reaction (PCR) may be used.
Treatment options
Because this illness is not caused by bacteria, antibiotics do not help treat West Nile virus infection. At this time, there are no FDA-approved shots or medicines to stop or treat West Nile Virus infection. Most people with mild symptoms get better without any treatment. Use of over-the-counter pain relievers may assist during this period of infection. People with severe West Nile Virus infections may need to go to the hospital. Severe cases of West Nile Virus may be treated with intravenous fluids and prophylactic care to prevent the onset of other infections, like pneumonia.
Where to find medical care for West nile virus disease?
Directions to Hospitals Treating West nile virus disease
What to expect (Outlook/Prognosis)?
In general, the outcome of a mild West Nile virus infection is excellent.
For patients with severe cases of West Nile virus infection, the outlook is more uncertain. West Nile encephalitis or meningitis may lead to brain damage and death. Approximately 10% of patients with brain inflammation do not survive.
Possible complications
Complications from mild West Nile virus infection are very rare.
Complications from severe West Nile virus infection include:
- Brain damage
- Permanent muscle weakness (sometimes similar to polio)
- Death
Prevention
- Use bug spray. Look for permethrin or DEET on the label. Read and follow the directions. Do not use it on children less than 2 years old.
- If you use bug spray, wash your clothes before you wear them again.
- Get rid of standing water (flower pots, buckets, barrels, and tire swings), as mosquitoes can breed in standing water.
- Change water in outdoor pet dishes and bird baths often.
- Keep children's wading pools empty and on their sides when not in use.
- Stay inside during times when there are a lot of mosquitoes (evening or dusk until dawn).
- Wear long-sleeved shirts and long pants.
- Put screens on your windows and doors.
- Don't wear perfume or cologne when you go outside for a long time.
- Check to see if there is a mosquito control program in your area.