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Encephalitis

Encephalitis is irritation and swelling (inflammation) of the brain, most often due to infections.

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Causes

Encephalitis is a rare condition. It occurs more often in the first year of life and decreases with age. The very young and older adults are more likely to have a severe case.

Encephalitis is most often caused by a virus. Many types of viruses may cause it. Exposure can occur through:

Different viruses occur in different geographic locations. Many cases occur during a certain season.

Encephalitis caused by the herpes simplex virus is the leading cause of more severe cases in all ages, including newborns.

Routine vaccination has greatly reduced encephalitis due to some viruses, including:

Other viruses that cause encephalitis include:

After the virus enters the body, the brain tissue swells. This swelling may destroy nerve cells, and cause bleeding in the brain and brain damage.

Other causes of encephalitis may include:

Symptoms

Some people may have symptoms of a cold or stomach infection before encephalitis symptoms begin.

When this infection is not very severe, the symptoms may be similar to those of other illnesses:

Other symptoms include:

Symptoms in newborns and younger infants may not be as easy to recognize:

Emergency symptoms:

Exams and Tests

The health care provider will perform a physical exam and ask about symptoms.

Tests that may be done include:

Treatment

The goals of treatment are to provide supportive care (rest, nutrition, fluids) to help the body fight the infection, and to relieve symptoms.

Medicines may include:

If brain function is severely affected, physical therapy and speech therapy may be needed after the infection is controlled.

Outlook (Prognosis)

The outcome varies. Some cases are mild and short, and the person fully recovers. Other cases are severe, and permanent problems or death is possible.

The acute phase normally lasts for 1 to 2 weeks. Fever and symptoms gradually or suddenly disappear. Some people may take several months to fully recover.

Possible Complications

Permanent brain damage may occur in severe cases of encephalitis. It can affect:

When to Contact a Medical Professional

Go to the emergency room or call 911 or the local emergency number if you have:

Prevention

Children and adults should avoid contact with anyone who has encephalitis.

Controlling mosquitoes (a mosquito bite can transmit some viruses) may reduce the chance of some infections that can lead to encephalitis.

Children and adults should get routine vaccinations for viruses that can cause encephalitis. People should receive specific vaccines if they are traveling to places such as parts of Asia, where Japanese encephalitis is found.

Vaccinate animals to prevent encephalitis caused by the rabies virus.

Related Information

Meningitis
Tick bite
Chickenpox
Shingles
Measles
Mumps
Rubella
Rabies
West Nile virus infection
Vaccines - immunizations
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References

Beckham JD, Tyler KL. Encephalitis. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 89.

Bronstein DE, Glaser CA. Encephalitis and meningoencephalitis. In: Cherry JD, Harrison GJ, Kaplan SL, Steinbach WJ, Hotez PJ, eds. Feigin and Cherry's Textbook of Pediatric Infectious Diseases. 8th ed. Philadelphia, PA: Elsevier; 2019:chap 36.

Lissauer T, Carroll W. Infection and immunity. In: Lissauer T, Carroll W, eds. Illustrated Textbook of Paediatrics. 6th ed. Philadelphia, PA: Elsevier; 2022:chap 15.

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Review Date: 7/28/2022  

Reviewed By: Charles I. Schwartz MD, FAAP, Clinical Assistant Professor of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, General Pediatrician at PennCare for Kids, Phoenixville, PA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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