Get exclusive member benefits & effect social change. Join Today
Encephalitis is an inflammation of the brain tissue. It’s most often caused by viral infections. In some cases, bacterial infections can cause encephalitis.
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.
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:
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:
The groups most at risk of encephalitis are:
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.
The symptoms of encephalitis can range from mild to severe.
Mild symptoms include:
Severe symptoms include:
Infants and young children show different symptoms. Call a doctor immediately if your child is experiencing the following signs:
Your doctor will first ask you about your symptoms. They may perform the following tests if encephalitis is suspected.
In this test, your doctor will collect a sample of spinal fluid and test it for signs of infection.
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.
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 include:
You may need to be hospitalized during treatment, especially with brain swelling and seizures.
Most people who are diagnosed with severe encephalitis will experience complications. Complications resulting from encephalitis can include:
Complications are more likely to develop in certain groups, such as:
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:
Depending on the type and severity of encephalitis, it may be necessary to receive additional therapy, including:
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.
Written by: Shannon Johnson
Published on: Jul 09, 2012
Medically reviewed on: Mar 31, 2017: Tyler Walker, MD
Enter your symptoms in our Symptom Checker to find out possible causes of your symptoms. Go.
Enter any list of prescription drugs and see how they interact with each other and with other substances. Go.
Enter its color and shape information, and this tool helps you identify it. Go.
Find information on drug interactions, side effects, and more. Go.
From companies that meet the high standards of service and quality set by AARP.
Members save 10% on the monthly service charge of qualified AT&T wireless plans.
Members pay $9.50 for Regal ePremiere Tickets purchased online.
Members earn points on select Walgreens-brand health and wellness products.
Join or renew today! Members receive exclusive member benefits & affect social change.