Encephalitis can often be caused by an infection. Some common ones are:

  • Herpes simplex virus (HSV)
  • The varicella zoster virus, which causes chickenpox, shingles, Measles, Mumps, and rubella
  • Viruses carried by mosquitoes such as West Nile or Eastern equine encephalitis

It can also be caused by a problem with the immune system, such as a tumor or having an infection in the body before.

Risk Factors

Some things that may raise the risk of encephalitis are:

  • Spending time in places where viruses carried by mosquitoes or ticks are common
  • Not getting vaccinated for diseases that can cause encephalitis
  • Having a weakened immune system



A person with encephalitis may have:

  • Nausea and vomiting
  • Diarrhea or belly pain
  • Fever
  • Stiff neck or headache
  • Sleepiness
  • Loss of feeling or numbness in the body
  • Confusion or personality changes
  • Seizures


The doctor will ask about your symptoms and health history. A physical exam will be done.

Blood tests will be done to look for signs of infection. A lumbar puncture may be done to test the fluid around the brain and spine.

Images may be taken of the brain to look for changes. This can be done with:

  • CT scan
  • MRI scan



The goal of treatment is to rid the body of the virus that is causing the problem. There are not many ways to treat all viruses. They take time to leave the body.

If a virus cannot be treated then treatment will focus on helping the body until the virus has passed.

These medicines may be given:

  • Antiviral drugs to make the illness last a shorter time
  • Steroids to ease swelling in the brain
  • Medicines to ease pressure in the head
  • Anti-seizure medicine to prevent and treat seizures


To lower your chances of getting encephalitis:

  • Make sure your vaccinations are up to date.
  • Protect yourself from mosquito and tick bites, especially in high risk areas.

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

Edits to original content made by Denver Health.