Encephalitis is an inflammation (swelling) of the brain. Encephalitis is usually caused by a virus, but other things (including bacteria) can also cause it.
Encephalitis (pronounced: in-seh-fuh-LYE-tus) is typically caused by three different groups of viruses:
Some cases of encephalitis are mild and symptoms only last for a short time. However, it is possible to develop a severe case of encephalitis that can be serious and possibly even life threatening. When a person has encephalitis, his or her brain becomes inflamed (inflammation means swelling and irritation).
Infection with many different viruses can lead to encephalitis. So how contagious the infection is depends on which virus caused it. Viruses like West Nile are only transmitted through the bite of infected insects; it's not possible to catch them from other people. But viruses like EBV are passed from person to person.
Even if someone catches a virus that can cause encephalitis, that does not mean that person will automatically develop the condition. In fact, very few people who are infected with these viruses actually develop encephalitis.
Encephalitis may cause fever, headache, poor appetite, loss of energy, or just a general sick feeling. In more severe cases, other symptoms might occur, including:
When encephalitis happens after a common illness like chickenpox, the signs and symptoms of that illness usually come before symptoms of inflammation in the brain. But encephalitis can also appear without warning. If you have symptoms of encephalitis, get in touch with your doctor right away.
To diagnose encephalitis, the doctor may take blood samples and perform a spinal tap (also called a lumbar puncture), a procedure that involves inserting a very thin needle into the lower back to remove some cerebrospinal fluid (CSF) that surrounds the brain and spinal cord. The samples will be sent to a laboratory to be checked for viruses or bacteria.
A brain scan (an MRI or a CT scan) might be done to look for inflammation, and the doctor also might order an electroencephalogram (EEG), a test that records brain waves and can reveal any abnormalities consistent with encephalitis.
Treatment for encephalitis depends on the virus or other germ that caused it. Teens with mild cases of encephalitis can recover at home as long as they're watched carefully by a parent or other adult in the household. Most cases of encephalitis just run their course and the person gets better without treatment.
Some viruses that cause encephalitis can be treated with medication. For example, acyclovir, an antiviral drug, can help treat encephalitis caused by the herpes simplex virus. In addition, steroid medications can be used to reduce swelling in the brain (these aren't the same as the dangerous performance-enhancing steroids that some athletes use). Because antibiotics are not effective against viruses, they're not used to treat viral encephalitis.
Severe cases of encephalitis require a hospital stay so the patient can be carefully monitored and medical treatment is close at hand if needed. For people who have had severe encephalitis that has affected some of the brain's functions, doctors may recommend physical therapy or speech therapy to help with recovery.
The worst symptoms of encephalitis generally last up to 1 week, but full recovery may take weeks or longer. Because encephalitis affects the brain, people with severe cases can sometimes develop problems like seizures, difficulties with muscle coordination, and learning disabilities.
The best way to prevent encephalitis is to avoid getting infected with the viruses or other germs that can cause it. Regular hand washing will help limit the spread of some of these germs. Staying as healthy as possible by eating a balanced diet and getting plenty of rest can help keep your immune system in shape. Immunizations are also an important way to protect people from diseases like chickenpox and measles.
In areas where viruses and other germs are transmitted by insect bites, protect yourself by wearing long sleeves and pants and applying an insect repellent. Also, try to avoid unnecessary outdoor activities at dawn and dusk when mosquitoes are most likely to bite.
Reviewed by: Nicole A. Green, MD
Date reviewed: April 2013
|Centers for Disease Control and Prevention (CDC) The CDC (the national public health institute of the United States) promotes health and quality of life by preventing and controlling disease, injury, and disability.|
|Immunization Action Coalition This organization is a source of childhood, adolescent, and adult immunization information as well as hepatitis B educational materials.|
|CDC: Preteen and Teen Vaccines CDC site provides materials in English and Spanish for parents, teens, preteens, and health care providers about vaccines and the diseases they prevent.|
|CDC: Travelers' Health Look up vaccination requirements for travel destinations, get updates on international outbreaks, and more, searachable by country.|
|Hand Washing Did you know that the most important thing you can do to keep from getting sick is to wash your hands? If you don't wash your hands frequently, you can pick up germs from other sources and then infect yourself.|
|Rocky Mountain Spotted Fever Rocky Mountain spotted fever (RMSF) is a disease caused by a bacteria that is carried by certain types of ticks. Learn about the signs and symptoms of RMSF and tips for preventing infection in this article.|
|Mononucleosis It's sometimes called "the kissing disease," but kissing is just one of the ways that someone can catch mono.|
|Spinal Tap A spinal tap (also called a lumbar puncture) is a medical test that involves taking a small sample of cerebrospinal fluid for examination. Find out what's involved in this article for teens.|
|Magnetic Resonance Imaging (MRI) An MRI is a painless test that produces detailed pictures of the body's organs and structures. This article for teens explains how it works and why you might need one.|
|West Nile Virus You've probably heard about West Nile virus and know that mosquitoes have something to do with it. Learn more about the virus, including how you can protect yourself.|
|Cold Sores (HSV-1) Cold sores (also known as fever blisters) are pretty common and lots of people get them. So what causes them and what can you do?|
|Meningitis You may be wondering what the deal is with meningitis because you've heard frightening stuff about meningitis outbreaks in the news.|
|Lyme Disease Lyme disease can be treated if it's caught early. So read this to find out what causes it, how it's treated, and how to prevent it.|
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