Medically Reviewed by Dr. K on 18 March 2021

What is Encephalitis?

Encephalitis is an infection or an autoimmune response that causes inflammation of the active tissues of the brain.

It may be very severe when it develops, causing personality changes, seizures, fatigue, and other effects based on which area of the brain is impacted.

The most susceptible are children, the elderly, and those with a weakened immune system. The condition is often referred to as viral encephalitis and it is normally triggered by one or many viral infections.

Many patients with encephalitis recover fully. The virus involved and the severity of the inflammation determine the most appropriate treatment and the patient’s likelihood of recovery.

The virus immediately affects the brain cells in acute encephalitis. Within one or two weeks after developing a virus or bacterial infection, the brain and spinal cord become inflamed, resulting in para-infectious encephalitis.

What Causes Encephalitis?

Influenza, herpes simplex, measles, mumps, rubella, rabies, chickenpox, and arbovirus infections, including the West Nile virus, may also trigger viral encephalitis.

One of the most common and dangerous causes of viral encephalitis is the herpes simplex type 1 virus. Herpes-related encephalitis may develop quickly, resulting in headaches, behavioral changes, and even coma or death. It occurs when the herpes simplex type 1 virus spreads to the brain instead of going across the body to the skin’s surface and causing a cold sore, which is the most frequent sign. Herpes encephalitis may be fatal if not diagnosed and treated early. If you have cold sores, you are not more prone to have encephalitis.

Another kind of viral encephalitis is arbovirus encephalitis. It’s triggered by a variety of viruses spread by insects (such as mosquitoes and ticks). Arboviral diseases, unlike herpes, are sporadic, arising mainly in the summer and early fall, and are localized in particular geographic areas, such as St. Louis encephalitis.

Encephalitis is triggered by viral, fungal, infectious, or rickettsial diseases in severe circumstances. Encephalitis may be caused by cancer or by reactions to such medications or chemicals.


What Are the Symptoms of Encephalitis?

Encephalitis usually presents in a sudden and severe manner. Symptoms include:

  • Fever
  • Headaches
  • Confusion
  • Weakness in one or more areas of the body
  • Drowsiness and lethargy
  • Personality changes – more irritable, emotional outbursts
  • Seizures
  • Bulging soft spots in the head of children
  • Coma

When you or someone you know is experiencing either of these signs, get medical help right away.


Referenced on 2.3.2021:

  1. The Mayo Clinic.
  2. Nemours Foundation.
  3. National Institute of Neurological Disorders and Stroke.
  4. emedicine.com.
  5. https://www.webmd.com/a-to-z-guides/understanding-encephalitis-basics
  6. https://www.webmd.com/a-to-z-guides/understanding-encephalitis-symptoms

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