encephalitis

American  

[en-sef-uh-lahy-tis] / ɛnˌsɛf əˈlaɪ tɪs /

noun

Pathology.

1. inflammation of the substance of the brain.

2. Also called encephalitis lethargica.  a form of this condition, caused by a filterable virus and characterized by apathy and abnormal sleepiness; sleeping sickness.

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encephalitis British  

/ ˌɛnkɛf-, ˌɛnsɛfəˈlaɪtɪs, ˌɛnsɛfəˈlɪtɪk /

noun

1. inflammation of the brain

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encephalitis Scientific  

/ ĕn-sĕf′ə-lī′tĭs /

1. Inflammation of the brain, usually caused by infection with a virus.

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encephalitis Cultural  

1. An inflammation of the brain. Encephalitis may be caused by a virus or lead poisoning, or it may be a complication of another disease, such as influenza or measles. Encephalitis can cause permanent brain damage or death. It is also possible, however, to recover from it completely.

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Other Word Forms

• encephalitic
  adjective
• postencephalitic
  adjective
• pseudoencephalitic
  adjective

Etymology

Origin of encephalitis

First recorded in 1835–45; encephal- + -itis

Explanation

Encephalitis is a condition that causes the brain to swell and become irritated or inflamed. Most cases of encephalitis result from a virus. The term encephalitis comes from the Greek enkephalos, "brain," and the medical suffix -itis, used for diseases characterized by inflammation. Certain kinds of infections or disorders of the immune system can result in this inflammation of the brain. Encephalitis is quite rare, and though it's often so mild that it causes no symptoms, it can be serious.

Example Sentences

The findings, published in Nature Communications, explain how viruses responsible for illnesses such as polio, encephalitis, myocarditis, and even the common cold take control of cellular machinery to copy themselves.

From Science Daily • May 13, 2026

There are allusions to the tragedies that befell him: the loss of a young daughter to measles encephalitis and his son’s near-fatal accident.

From The Wall Street Journal • Mar. 24, 2026

These infections were marked by encephalitis and frequently resulted in death, highlighting the increased pathogenic potential of this transmission route.

From Science Daily • Jan. 5, 2026

In rare cases chicken pox can cause a swelling of the brain, called encephalitis; an inflammation of the lungs, called pneumonitis; and stroke, which can result in hospitalisation and - very rarely - death.

From BBC • Aug. 28, 2025

I slip off my flats and walk down the front porch steps, while Mother calls out for me to put my shoes back on, threatening ringworm, mosquito encephalitis.

From "The Help" by Kathryn Stockett