West Nile Virus

What is West Nile virus?

The West Nile virus is a virus that is primarily spread through mosquitoes. It is the most common mosquito-borne virus in the United States. The majority of those who are affected only experience mild symptoms, but the virus becomes dangerous when it enters the brain. About one of every 150 who are infected with this disease see it enter the brain and bring severe symptoms. 

What are the symptoms of West Nile virus?

The majority of those who are infected, eight out of ten, do not experience any symptoms. A lower percentage of affected people will develop symptoms such as fevers, headaches, body aches, joint pain, vomiting, diarrhea, and rashes. If these are the only symptoms present, a full recovery is possible and usually happens. 

A very small minority of those with West Nile virus develop serious, life-threatening symptoms. One of every 150 people infected will have encephalitis, which is inflammation of the brain, or meningitis. These conditions bring symptoms such as high fever, headaches, neck stiffness, stupor, disorientation, comas, tremors, convulsions, muscle weakness, vision loss, numbness, and paralysis. These two illnesses are the most common in those who have weakened immune systems, and people above the age of 60 are at the highest risk.

What causes West Nile virus?

This illness is most commonly spread through mosquitoes, which carry the disease after feeding on infected birds. In a smaller number of cases West Nile virus has been spread through blood transfusion, organ transplants, from mother to child through pregnancy, and exposure in a lab setting. 

How is West Nile virus diagnosed?

A physical exam is usually enough for a diagnosis. It can be confirmed through lab tests, usually blood tests. Lumbar punctures and brain tests will be used to diagnose meningitis and encephalitis. 

What are the treatments for West Nile virus?

There is no specific treatment for this virus. Symptoms can be managed, and hospitalization may be necessary for those who develop severe symptoms. It is especially important to be hospitalized if one has developed encephalitis or meningitis. 

Where can I find out more about West Nile virus?

• • Medline Plus
  • CDC
  • Mayo Clinic