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

Example Sentences

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

Mark, from Omagh in County Tyrone, also developed encephalitis, secondary to the meningitis, but fought through it all.

From BBC • Mar. 20, 2026

The clinical outcomes included neurologic conditions such as seizures, encephalitis, altered mental status, ataxia/movement disorders, vision changes, dizziness, headache, and sleeping disorders.

From Science Daily • Jan. 5, 2026

Measles can cause encephalitis, or inflammation of the brain.

From Los Angeles Times • Jun. 26, 2025

In some areas of the United States the mosquito vector of western equine encephalitis has developed resistance.

From "Silent Spring" by Rachel Carson