What Is Encephalitis?
Encephalitis is an inflammation of the brain tissue. It’s most
often caused by viral infections. In some cases, bacterial infections can cause
There are two main types of encephalitis: primary and secondary.
Primary encephalitis occurs when a virus directly infects the brain and spinal
cord. Secondary encephalitis occurs when an infection starts elsewhere in the
body and then travels to your brain.
Encephalitis is a rare yet serious disease that can be life-threatening.
You should call your doctor immediately if you have symptoms of encephalitis.
What Causes Encephalitis?
Many different viruses can cause encephalitis. It’s helpful to
categorize the potential causes into three groups: common viruses, childhood
viruses, and arboviruses.
The most common virus that causes encephalitis in developed
countries is herpes simplex.
The herpes virus typically travels through a nerve to the skin, where it causes
a cold sore. In rare cases, however, the virus goes to the brain.
This form of encephalitis will often damage the temporal lobe
(the part of the brain that controls memory and speech). It can also affect the
frontal lobe (the part that controls emotions and behavior). Encephalitis caused
by herpes is dangerous and can lead to severe brain damage.
Other common viruses that can cause encephalitis include:
- Epstein-Barr virus
- cytomegalovirus (CMV)
Vaccines prevent the childhood viruses that used to commonly
cause encephalitis. Therefore, these types of encephalitis are rare today.
Some childhood viruses that can cause encephalitis include:
Arboviruses are viruses carried by insects. The type of arbovirus
that’s transmitted depends on the insect. Below are different types:
encephalitis (also called La Crosse encephalitis): transmitted through mosquito
bites and mainly affects children. It causes few to no symptoms.
Louis encephalitis: occurs in the rural Midwest and southern
states. It’s generally a mild virus and causes few symptoms.
Nile virus: most often found in Africa and the Middle East.
However, it can occur in the United States. It’s usually relatively mild,
causing flu-like symptoms. However, it can be fatal among older adults and people
with weak immune systems.
- Colorado encephalitis
(also called Colorado tick fever): transmitted by the female wood tick. It’s
typically a mild disease, and most people will recover quickly.
equine encephalitis: spread by mosquitoes. It affects both humans
and horses. Although rare, it has a 33 percent mortality rate.
forest disease: transmitted through tick bites. People can also get it by
drinking raw milk from goats, sheep, or cows. Hunters, campers, and farmers are
most at risk for getting this disease.
What Are the Risk Factors for Encephalitis?
The groups most at risk of encephalitis are:
- older adults
- children under the age of 1
- people with weak immune systems
You may also have a higher risk of getting encephalitis if you
live in an area where mosquitos or ticks are common.
You’re more likely to get encephalitis from an insect bite in the
summer or fall.
What Are the Symptoms of Encephalitis?
The symptoms of encephalitis can range from mild to severe.
Mild symptoms include:
- stiff neck
- lethargy (exhaustion)
Severe symptoms include:
- very high fever (103°F or higher)
- slower movements
- sensitivity to light
Infants and young children show different symptoms. Call a doctor
immediately if your child is experiencing the following signs:
- bulging fontanel (soft spot in the scalp)
- constant crying
- body stiffness
- poor appetite
How Is Encephalitis Diagnosed?
Your doctor will first ask you about your symptoms. They may
perform the following tests if encephalitis is suspected.
Spinal Tap or Lumbar Puncture
In this test, your doctor will collect a sample of spinal fluid
and test it for signs of infection.
Brain Imaging with CT Scan or MRI
These tests detect changes in brain structure. They can rule out
other possible explanations for symptoms, such as a tumor or stroke.
An EEG uses electrodes (small metal discs with wires) attached to
the scalp to record brain activity.
A blood test can reveal signs of a viral infection.
In a brain biopsy, your doctor will remove small samples of brain
tissue to test for infection. This procedure is rarely performed because there’s
a high risk of complications. It’s usually only done if doctors can’t determine
the cause the brain swelling or if treatment isn’t working.
How Is Encephalitis Treated?
Anti-viral medications can help treat herpes encephalitis.
However, they aren’t effective in treating other forms of encephalitis.
Instead, treatment often focuses on relieving symptoms. These treatments may
- pain killers
- corticosteroids (to reduce brain inflammation)
- mechanical ventilation (to help with breathing)
- lukewarm sponge baths
- anticonvulsants (to prevent or stop seizures)
- sedatives (for restlessness, aggressiveness, and
- fluids (sometimes through an IV)
You may need to be hospitalized during treatment, especially with
brain swelling and seizures.
What Are the Complications Associated with Encephalitis?
Most people who are diagnosed with severe encephalitis will
experience complications. Complications resulting from encephalitis can
- loss of memory
- behavioral/personality changes
- physical weakness
- intellectual disability
- lack of muscle coordination
- vision problems
- hearing problems
- speaking issues
- difficulty breathing
Complications are more likely to develop in certain groups, such
- older adults
- people who have had coma-like symptoms
- people who didn’t get treatment right away
What Is the Long-Term Outlook for Someone with Encephalitis?
Your outlook will depend on the severity of the inflammation. In
mild cases of encephalitis, the inflammation will likely disappear in a few days.
However, severe cases may require weeks or months to get better. It can
sometimes cause permanent brain damage or even death.
People with encephalitis may also experience:
- loss of brain function
- problems with speech, behavior, memory, and
Depending on the type and severity of encephalitis, it may be
necessary to receive additional therapy, including:
therapy: to improve strength, coordination, balance, and flexibility
therapy: to help redevelop everyday skills
therapy: to help relearn muscle control needed for talking
to help with coping strategies, mood disorders, or personality changes
Can Encephalitis Be Prevented?
Encephalitis isn’t always preventable, but you can lower your
risk by getting vaccinated for encephalitis, where available. You should also
make sure your children receive vaccinations for the viruses that can cause
encephalitis. When outside, it’s important to use mosquito repellant. Wear long
sleeves and pants in areas where ticks and mosquitos are common.