West Nile Virus Causes, Symptoms, Diagnosis, Treatment, Prevention

West Nile Virus Causes, Symptoms, Diagnosis, Treatment, Prevention


What is West Nile virus? How is west nile virus spread?


West Nile virus causes an infection that is spread by certain kinds of mosquitoes camera. Most often, mosquitoes get infected when they bite infected birds. Then the mosquitoes spread the virus when they bite people or other animals, such as horses. West Nile cannot spread from these animals to people or from person to person through casual contact.


West Nile Virus Causes, Symptoms, Diagnosis, Treatment, Prevention
West Nile Virus

West Nile can spread through an organ transplant or a blood transfusion. So all donated blood in the United States is screened to see if the virus is present. Some evidence suggests that West Nile can spread from a mom to her baby during pregnancy, at birth, or through breast milk. But the CDC still recommends that women breast-feed, because the risk of spreading the virus to babies is unclear and the benefits of breast-feeding are known.

Most people who have West Nile have no symptoms. Or the symptoms may be so mild that people may not even realize that they have the virus. In rare cases, West Nile can lead to swelling of the brain (encephalitis), swelling of the spinal cord (myelitis), or swelling of the tissues around the brain and spinal cord (meningitis). But very few people with West Nile will get a severe illness that affects the brain or spinal cord.

Anyone who is bitten by a mosquito may get West Nile. Most of the time people fully recover from it. But permanent problems such as seizures, memory loss, and brain damage can occur, especially in children and older people. As you get older, you have a higher risk for getting encephalitis and other serious problems from West Nile. Of the people who have serious problems, those older than age 70 have the biggest risk of dying from them. In a few cases, West Nile can be fatal.

How is West Nile virus transmitted?


The principal transmission cycle of West Nile virus involves several species of mosquitoes and various species of birds. Mosquitoes become infected with West Nile virus when they feed on a bird carrying the virus in its blood. After 10 to 14 days, the virus can be transmitted to another bird, person, or other animal that the mosquito bites. During blood feeding the mosquito injects the virus, contained in its saliva, into the bird, animal, or person – where the virus replicates and may cause illness.

Causes of West Nile Virus


Infection transmitted by mosquitoes 


Typically, West Nile virus spreads to humans and animals via infected mosquitoes. Mosquitoes become infected when they feed on infected birds. You can't get infected by touching or kissing a person with the virus.

Most West Nile virus infections occur during warm weather, when mosquito populations are active. The incubation period — the period between when you're bitten by an infected mosquito and the appearance of signs and symptoms of the illness — ranges from three to 14 days.

West Nile virus is present in areas such as Africa, parts of Asia and the Middle East. It first appeared in the United States in the summer of 1999 and since then has been found in all 48 contiguous states.

West Nile Virus Causes, Symptoms, Diagnosis, Treatment, Prevention


Other possible routes of transmission 


In a few cases, West Nile virus may have been spread through other routes, including organ transplantation and blood transfusion. However, blood donors are screened for the virus, substantially reducing the risk of infection from blood transfusions.

There have also been reports of possible transmission of the virus from mother to child during pregnancy or breast-feeding, but these have been rare and not conclusively confirmed.

What are the symptoms of West Nile Virus?


About 80 out of 100 people who have West Nile have no symptoms.2 When symptoms do appear, they begin 3 to 14 days after the mosquito bite. Mild symptoms include:

  • A fever.
  • Headaches, body aches, or pain in your eyes.
  • A rash, usually on the chest, back, and arms.
  • Feeling very tired.
  • Not feeling hungry.
  • Feeling sick to your stomach or throwing up.
  • Swollen glands (lymph nodes), in rare cases.
In mild cases of West Nile, symptoms usually last for 3 to 6 days. If you get a more severe case of West Nile, symptoms can last for weeks or months. Severe cases that involve problems with the brain and spinal cord are rare, but they may cause:

  • Headaches.
  • A high fever.
  • A stiff neck or paralysis.
  • Confusion.
  • Reduced attention to surroundings.
  • Tremors, convulsions, or muscle weakness.
  • A coma.
In rare cases, West Nile virus can cause death.

When to see a doctor

Mild symptoms of West Nile fever usually resolve on their own. If you experience signs or symptoms of serious infection, such as severe headaches, a stiff neck, disorientation or confusion, seek medical attention right away. A serious West Nile virus infection generally requires hospitalization.

How is West Nile virus diagnosed?


Your doctor can confirm the presence of West Nile virus or a West Nile-related illness, such as meningitis or encephalitis, by performing one of the following tests:

Laboratory tests


If you're infected, a blood test may show a rising level of antibodies to the West Nile virus. Antibodies are immune system proteins that attack foreign substances, such as viruses. A positive ribonucleic acid (RNA) test for the West Nile virus also is an indicator that you have the virus.

Lumbar puncture (spinal tap)


The most common way to diagnose meningitis is to analyze the cerebrospinal fluid surrounding your brain and spinal cord. A needle inserted between the lower vertebrae of your spine is used to extract a sample of fluid for laboratory analysis. The fluid sample may show an elevated white cell count — a signal that your immune system is fighting an infection — and antibodies to the West Nile virus.

Brain tests


In some cases, an electroencephalography (EEG) — a procedure that tests your brain's activity — or an MRI scan can help detect brain inflammation.

Treating West Nile virus


Supportive therapy 


Most people recover from West Nile virus without treatment. Over-the-counter pain relievers can help ease mild headaches and muscle aches.

Use caution when giving aspirin to children or teenagers. Though aspirin is approved for use in children older than age 2, children and teenagers recovering from chickenpox or flu-like symptoms should never take aspirin. This is because aspirin has been linked to Reye's syndrome, a rare but potentially life-threatening condition, in such children.

There's no direct cure for encephalitis or meningitis, but you may need supportive therapy in a hospital with intravenous fluids and medicines to prevent other types of infections.

Interferon therapy 


Scientists are investigating interferon therapy — a type of immune cell therapy — as a treatment for encephalitis caused by West Nile virus. Some research shows that people who receive interferon may recover better than those who don't receive the drug, but more study is needed.

How can you prevent West Nile Virus infection?


You can contact your local health department for the latest information on the virus in your area. It’s also a good idea to take steps to lower your risk of getting a mosquito bite:

West Nile Virus Causes, Symptoms, Diagnosis, Treatment, Prevention

Apply mosquito repellent containing an Environmental Protection Agency-registered insect repellent to your skin and clothing. Choose the concentration based on the hours of protection you need — the higher the percentage (concentration) of the active ingredient, the longer the repellent will work. Follow the directions on the package, paying special attention to recommendations for use on children.

Use insect repellent when you go outdoors in the late spring, summer, and early fall.

Wear long-sleeved shirts and long pants if you know that you will be in areas with lots of mosquitoes or where you know West Nile virus has been found.

Do not leave puddles or open containers of water near your house, because mosquitoes breed in standing water.

Stay indoors at dawn, dusk, and in the early evening when mosquitoes are the most active.

When outside, cover your infant's stroller or playpen with mosquito netting.

A West Nile virus vaccine is available for horses only. If you own horses, you may think about getting the vaccine for them. The death rate from West Nile is much higher in horses than in humans.

Researchers are working to create a vaccine that prevents West Nile virus in humans.

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