Encephalitis is an acute inflammation of the brain. The majority of encephalitis cases result from either a viral infection or a person’s immune system mistakenly attacking their brain tissue.

Encephalitis is a rare and serious condition. In the United States, fewer than 1 in every 14,000 people require hospitalization for encephalitis every year, according to 2014 research.

Viruses cause about 70% of encephalitis cases, with young children (ages 1 year and under) and older adults (ages 65 years and over) being the most susceptible age demographics.

In rare cases, bacteria, fungi, and parasitic worms can cause encephalitis.

This article will look at the symptoms, causes, treatments, and complications of encephalitis.

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Encephalitis is an acute inflammation or swelling of the brain, typically resulting from a viral infection or the body’s immune system mistakenly attacking brain tissue.

The most common cause is a viral infection. Inflammation in the brain occurs due to the body’s attempt to fight off the virus. Encephalitis occurs in 1 in every 1,000 cases of measles.

Encephalitis typically begins with a fever and headache. The symptoms rapidly worsen, and there may be seizures, confusion, drowsiness, loss of consciousness, and even coma.

Most people with mild cases of encephalitis can make a full recovery. However, encephalitis can be life threatening and very serious. A 2020 study of all-cause encephalitis found that almost 10% of people died during hospitalization.

A person’s outlook with encephalitis depends on various factors, including the cause and severity of the disease, as well as the person’s age and health status.


Different types of encephalitis have different causes.

Typically, a person with encephalitis will experience some of the following:

Less common symptoms

An individual may experience neck stiffness. There may also be stiffness of the limbs, slow movements, and clumsiness. They may also feel drowsy and have a cough.

More serious cases

In more serious cases, a person may experience:

Signs and symptoms in infants

Initially, encephalitis is harder to detect in young children and babies.

Parents and caregivers should look out for:

  • vomiting
  • a bulge near the soft area on the top center of the head called the fontanel
  • incessant crying that does not get better when the child is picked up and comforted
  • body stiffness

Encephalitis can develop due to a direct brain infection with a virus, bacteria, or fungus. It can also occur when the immune system responds to a past infection and the immune system mistakenly attacks brain tissue.

There are three main categories of viruses that cause primary encephalitis:

Secondary encephalitis is often a complication of a viral infection. Symptoms start to appear days or even weeks after the initial infection. The person’s immune system treats healthy brain cells as foreign organisms and attacks them. It is not known why the immune system malfunctions in this way.

In more than 60% of encephalitis cases, the exact cause of the illness is unknown.

Risk factors

Anyone can contract encephalitis. However, certain groups of people are at higher risk. These include:

  • children
  • older adults
  • individuals with weakened immune systems
  • people who live in areas where mosquitoes and ticks are common

Older adults and those who do not receive prompt treatment have a higher risk of developing complications.

Complications may include:

  • loss of memory, especially among those who had HSV encephalitis
  • behavioral or personality changes, such as mood swings, bouts of frustration and anger, and anxiety
  • epilepsy
  • aphasia, language, and speech problems

Treatment for encephalitis focuses on treating underlying causes and alleviating symptoms.

Treatment options include:

  • Corticosteroids: Doctors may recommend steroid injections to reduce inflammation in the brain.
  • Antiviral medication: In cases of viral encephalitis, antiviral medications can treat the root cause of the condition.
  • Antibiotics: Antibiotics can treat bacterial infections that may cause encephalitis.
  • Antifungal medications: In cases of fungal encephalitis, antifungal medications can help.
  • Anticonvulsants: If encephalitis is causing seizures, these medications can reduce convulsions.
  • Surgery: If doctors determine that a tumor or other growth caused encephalitis, they may perform surgery to remove it.
  • Immunoglobulin therapy: During immunoglobulin therapy, a doctor will administer a solution containing a large number of antibodies from donated blood. This is often an IV administration.
  • Therapeutic plasma exchange: This process removes blood from the body and filters out antibodies to help prevent them from attacking the body. A doctor then replaces the person’s blood with albumin or donated blood. Albumin is a protein the liver creates.

Doctors may order several tests to diagnose encephalitis.

Imaging tests

A CT scan may be useful in detecting changes in brain structure. It can also rule out other causes, such as stroke, an aneurysm, or a tumor. However, an MRI is the best imaging option for encephalitis, as doctors can use it to identify the classic brain changes that suggest the condition.

An EEG that monitors the brain’s electrical activity may show sharp waves in one or both of the temporal lobes in people with encephalitis.

Lumbar puncture

A lumbar puncture, which takes a sample of cerebrospinal fluid from the spine, might reveal protein levels and white blood cell levels that are higher than expected.

A doctor might order a blood test if they suspect viral encephalitis.

A person should consult a doctor if they are experiencing symptoms of encephalitis. Prompt treatment is crucial for treating the condition.

Symptoms to watch for include:


Most people with mild cases of encephalitis recover without complications. However, some people have difficulties concentrating, experience changes in their behavior or speech, and may experience memory loss. The most common long-term complication is seizures, which occur in 10–20% of people over several decades.

Keeping up to date with vaccines is the most effective way of reducing the risk of developing encephalitis. These include vaccines for measles, mumps, rubella, and if the virus exists in a person’s area, Japanese encephalitis and tick-borne encephalitis.

In areas known to have mosquitoes that carry encephalitis-causing viruses, individuals should take measures to reduce the risk of being bitten.

Encephalitis is an acute inflammation or swelling of the brain, typically resulting from a viral infection or the body’s immune system mistakenly attacking brain tissue.

Viruses are the most common cause of encephalitis. They can include HSV, measles, and viruses spread by mosquitoes, ticks, and other insects.

Encephalitis typically begins with a fever and headache. The symptoms rapidly worsen, and there may be seizures, confusion, drowsiness, loss of consciousness, and possibly coma.

While most people with mild cases of encephalitis will recover, the disease can be life threatening.