Learn About Encephalitis

What is the definition of Encephalitis?

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

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What are the causes of Encephalitis?

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:

  • Breathing in droplets from the nose, mouth, or throat from an infected person
  • Contaminated food or drink
  • Mosquito, tick, and other insect bites
  • Skin contact

Different viruses occur in different 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:

  • Measles
  • Mumps
  • Polio
  • Rabies
  • Rubella
  • Varicella (chickenpox)

Other viruses that cause encephalitis include:

  • Adenovirus
  • Coxsackievirus
  • Cytomegalovirus
  • Eastern equine encephalitis virus
  • Echovirus
  • Japanese encephalitis, which occurs in Asia
  • West Nile virus

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:

  • An allergic reaction to vaccinations
  • Autoimmune disease
  • Bacteria such as Lyme disease, syphilis, and tuberculosis
  • Parasites such as roundworms, cysticercosis, and toxoplasmosis in people with HIV/AIDS and other people who have a weakened immune system
  • The effects of cancer
What are the symptoms of Encephalitis?

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:

  • Fever that is not very high
  • Mild headache
  • Low energy and a poor appetite

Other symptoms include:

  • Clumsiness, unsteady gait
  • Confusion, disorientation
  • Drowsiness
  • Irritability or poor temper control
  • Light sensitivity
  • Stiff neck and back (sometimes)
  • Vomiting

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

  • Body stiffness
  • Irritability and crying more often (these symptoms may get worse when the baby is picked up)
  • Poor feeding
  • Soft spot on the top of the head may bulge out more
  • Vomiting

Emergency symptoms:

  • Loss of consciousness, poor responsiveness, stupor, coma
  • Muscle weakness or paralysis
  • Seizures
  • Severe headache
  • Sudden change in mental functions, such as flat mood, impaired judgment, memory loss, or a lack of interest in daily activities
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What are the current treatments for Encephalitis?

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:

  • Antiviral medicines, if a virus caused the infection
  • Antibiotics, if bacteria is the cause
  • Antiseizure medicines to prevent seizures
  • Steroids to reduce brain swelling
  • Sedatives for irritability or restlessness
  • Acetaminophen for fever and headache

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

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What is the outlook (prognosis) for Encephalitis?

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.

What are the possible complications of Encephalitis?

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

  • Hearing
  • Memory
  • Muscle control
  • Sensation
  • Speech
  • Vision
When should I contact a medical professional for Encephalitis?

Go to the emergency room or call the local emergency number (such as 911) if you have:

  • Sudden fever
  • Other symptoms of encephalitis
How do I prevent Encephalitis?

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.

  • Apply an insect repellant containing the chemical, DEET when you go outside (but DO NOT use DEET products on infants younger than 2 months).
  • Remove any sources of standing water (such as old tires, cans, gutters, and wading pools).
  • Wear long-sleeved shirts and pants when outside, especially at dusk.

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.

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What are the latest Encephalitis Clinical Trials?
Physical Activity in People With Sequelae of Poliomyelitis : a Cross-sectional Study
Summary: People with disabilities are less physically active than the general population. At present, the physical activity level of people with poliomyelitis sequelae and their barriers to physical activity are unknown.~The aim of this study is to describe the physical activity level of people with poliomyelitis sequelae and their barriers to physical activity.
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A Phase 3, Open-label, Multicenter Study to Evaluate Long-term Immunogenicity and Boostability of Immune Responses in Adults Who Received Different Primary Vaccination Regimens of Pre-exposure Prophylaxis With Purified Chick-Embryo Cell Rabies Vaccine Administered Concomitantly or Separately From a Japanese Encephalitis Vaccine.
Summary: GlaxoSmithKline (GSK) Biologicals' Rabipur vaccine is indicated for active immunization against rabies in individuals of all ages. This includes pre-exposure prophylaxis (PrEP), in both primary series and booster dose, and post exposure prophylaxis.The aim of this extension study is to evaluate the long-term (up to approx.10 years) persistence and to assess the boostability of immune responses in ...
What are the Latest Advances for Encephalitis?
Kawasaki disease complicated with mild encephalitis/encephalopathy with a reversible splenial lesion: A case report and literature review.
Summary: Kawasaki disease complicated with mild encephalitis/encephalopathy with a reversible splenial lesion: A case report and literature review.
Rituximab in myasthenia gravis: efficacy, associated infections and risk of induced hypogammaglobulinemia.
Summary: Rituximab in myasthenia gravis: efficacy, associated infections and risk of induced hypogammaglobulinemia.
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Refractory Anti-NMDA Receptor Encephalitis in Early Pregnancy: A Case Report of Treatment Course and Pregnancy Outcomes.
Summary: Refractory Anti-NMDA Receptor Encephalitis in Early Pregnancy: A Case Report of Treatment Course and Pregnancy Outcomes.
Who are the sources who wrote this article ?

Published Date: August 29, 2020
Published By: Neil K. Kaneshiro, MD, MHA, Clinical Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

What are the references for this article ?

Bloch KC, Glaser CA, Tunkel AR. Encephalitis and myelitis. In: Cohen J, Powderly WG, Opal SM, eds. Infectious Diseases. 4th ed. Philadelphia, PA: Elsevier; 2017:chap 20.

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. 5th ed. Philadelphia, PA: Elsevier; 2018:chap 15.