West Nile Virus

By: Connor Sechrist

What to Know About the Disease

It was discovered in the West Nile District of Uganda in 1937, and later found in Africa, Asia, the Middle East and Europe. The West Nile virus now found across the continental United States, Canada, Central America and the Caribbean is an Israeli strain introduced into New York City in 1999. The more common symptoms are headaches, high fever, and a stiff neck. In other cases, the virus is a more serious neuro-invasive disease. Patients may experience a stiff neck, disorientation, unexplained confusion, and in some cases paralysis. Younger patients tend to get the former while older patients tend to experience the neuro-invasive symptoms.

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How Can You Get West Nile Virus?

Most people get infected with West Nile virus by the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then spread the virus to humans and other animals. In a very small number of cases, West Nile virus has been spread through blood transfusions, organ transplants, and from mother to baby during pregnancy, delivery, or breastfeeding. It can spread very easily and fast.

Is a Certain Standard Required to Get West Nile Virus?

Nearly 42,000 cases of West Nile virus disease have been reported in the United States since 1999. Of those, nearly 19,000 people have had neurological disease (infections of the brain or spinal cord) and more than 1,700 people have died. Many more cases of illness are not reported to CDC. Since 1999, an estimated 700,000 people in the United States have become ill due to West Nile virus infection. Anyone living in an area where West Nile virus is present in mosquitoes can get infected. West Nile virus has been detected in all lower 48 states (not in Hawaii or Alaska). Outbreaks have been occurring every summer since 1999. The risk of infection is highest for people who work outside or participate in outdoor activities because of greater exposure to mosquitoes. West Nile Virus does not choose who it infects, rather the host does such as a mosquito choosing to bite a American Male, A African women, or just a horse. However, elderly people who get infected are more likely to die than a young person. Reports indicate that less than 1% of persons who are infected with the West Nile virus develop severe illness; of individuals who have severe illness secondary to the infection, 3-15% die. Severe disease particularly affects the elderly.

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Signs, Symptoms, and Dignosis

About 20 percent of people develop a mild infection called West Nile fever. Common signs and symptoms of West Nile fever include:

  • Fever
  • Headache
  • Body aches
  • Fatigue
  • Back pain
  • Skin rash (occasionally)
  • Swollen lymph glands (occasionally)
  • Eye pain (occasionally)
In less than 1 percent of infected people, the virus causes a serious neurological infection. Such infection may include inflammation of the brain (encephalitis) or of both the brain and surrounding membranes (meningoencephalitis). Signs and symptoms of these diseases include:
  • High fever
  • Severe headache
  • Stiff neck
  • Disorientation or confusion
  • Stupor or coma
  • Tremors or muscle jerking
  • Lack of coordination
  • Convulsions
  • Pain
  • Partial paralysis or sudden muscle weakness
Signs and symptoms of West Nile fever usually last a few days, but signs and symptoms of encephalitis or meningitis can linger for weeks, and certain neurological effects, such as muscle weakness, may be permanent.

  • Laboratory tests. If you're infected, a blood test may show a rising level of antibodies to the West Nile virus. ...
  • Lumbar puncture (spinal tap). The most common way to diagnose meningitis is to analyze the cerebrovascular fluid surrounding your brain and spinal cord. ...
  • Brain tests.
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    Because a virus causes the condition, West Nile virus does not have a medical cure. However, you can take an over-the-counter pain reliever, such as ibuprofen or aspirin, to relieve muscle aches and headaches that can accompany West Nile virus. If you experience severe symptoms, such as brain swelling, your physician may give you intravenous fluids and medications to minimize potential infections.


    Here are CDC's top tips for avoiding West Nile virus. Use insect repellents that contain an EPA-registered active ingredient whenever you're outdoors. Wear long-sleeved shirts and long pants outdoors at dawn and dusk, or consider staying indoors during those times, when mosquitoes are most active.