Carl R. Darnall Army Medical Center - Health Library

Mosquito-Borne Viral Encephalitis

Pronunciation: En-sef-uh-LITE-is

Definition

Encephalitis is inflammation of the brain. Certain mosquito-borne viruses can lead to encephalitis. Examples of these viruses include:

Encephalitis
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Causes ^

The most common cause is being bitten by an infected mosquito. There are other, rarer causes such having a blood transfusion with infected blood.

Risk Factors ^

The greatest risk factors are spending time in areas where mosquitoes are present and not using insect repellent.

People who are age 50 years and older and those with a weakened immune system have a higher risk of developing serious symptoms.

Symptoms ^

Most people who become infected with one of these mosquito-borne viruses do not develop any symptoms.

If symptoms do occur, they are generally mild and may include flu-like symptoms such as:

  • Headache
  • Fever
  • Chills
  • Fatigue
  • Joint and muscle pain
  • Vomiting

While rare, a small percentage of people develop encephalitis and have serious, life-threatening symptoms such as:

  • High fever
  • Disorientation
  • Vision loss
  • Paralysis
  • Seizures
  • Coma

Diagnosis ^

In addition to taking your medical history and doing a physical exam, your doctor will ask you:

  • What kind of symptoms you are experiencing
  • Where you have been living or traveling to
  • Whether you have been exposed to mosquitoes

A blood test is commonly used to confirm the diagnosis of a mosquito-borne virus. Depending on the symptoms that you have, your doctor may order other tests such as:

Treatment ^

Treatment focuses on supportive care such as taking pain-relieving medications and fluid replacement to avoid dehydration.

Severe symptoms require hospitalization for treatment, which may include:

Prevention ^

The best way to reduce your chances of getting mosquito-borne viral encephalitis is to avoid being bitten by mosquitoes. Steps that can help include:

  • Limiting outside activities where mosquitoes are present
  • Wearing long sleeve shirts and long pants at dusk and dawn, when mosquitoes are most active
  • Using bug repellent that contains DEET
  • Emptying sources of standing water around the home such as bird baths and gutters, where mosquitoes may breed
  • Use proper mosquito netting at night. Look for netting treated with insecticide.
  • Repairing screens on your windows and doors to prevent mosquitoes from getting into your house

Mosquitoes can contract viruses by biting infected birds. If you see a dead bird, call the public health department. Do not touch the dead bird unless you are wearing disposable gloves.

RESOURCES:

Centers for Disease Control and Prevention
https://www.cdc.gov

National Institute of Neurological Disorders and Stroke
https://www.ninds.nih.gov

CANADIAN RESOURCES:

Alberta Health
http://www.health.alberta.ca

Health Canada
https://www.canada.ca

REFERENCES:

Eastern equine encephalitis. Centers for Disease Control and Prevention website. Available at: https://www.cdc.gov/easternequineencephalitis. Updated April 5, 2016. Accessed December 7, 2017.

Eastern equine encephalitis. EBSCO DynaMed Plus website. Available at:http://www.dynamed.com/topics/dmp~AN~T114677/Eastern-equine-encephalitis. Updated February 4, 2016. Accessed September 29, 2016.

Encephalitis: an overview. EBSCO Nursing Reference Center website. Available at:http://www.ebscohost.com/nursing/products/nursing-reference-center. Accessed December 7, 2017.

Meningitis and encephalitis information page. National Institute of Neurological Disorders and Stroke website. Available at: https://www.ninds.nih.gov/Disorders/All-Disorders/Meningitis-and-Encephalitis-Information-Page. Accessed December 7, 2017.

Mosquito avoidance. EBSCO DynaMed Plus website. Available at:http://www.dynamed.com/topics/dmp~AN~T115142/Mosquito-avoidance. Updated November 21, 2016. Accessed December 7, 2017.

Quick lesson about West Nile infection. EBSCO Nursing Reference Center website.http://www.ebscohost.com/nursing/products/nursing-reference-center. Accessed December 7, 2017.

West Nile virus infection. EBSCO DynaMed Plus website. Available at:http://www.dynamed.com/topics/dmp~AN~T114644/West-Nile-virus-infection. Updated November 6, 2017. Accessed December 7, 2017.

West Nile virus. Centers for Disease Control and Prevention website. Available at: https://www.cdc.gov/westnile/index.html. Updated December 5, 2017. Accessed December 7, 2017.

Last reviewed December 2017 by EBSCO Medical Review Board David L. Horn, MD, FACP  Last Updated: 12/20/2014