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

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

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

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

From BBC • Aug. 28, 2025

Measles can cause encephalitis, or inflammation of the brain.

From Los Angeles Times • Jun. 26, 2025

My father, who worked as a clerk at the General Post Office of Calcutta, died of encephalitis when I was sixteen.

From "Interpreter of Maladies" by Jhumpa Lahiri