encephalitis
noun
en·ceph·a·li·tis
in-ˌse-fə-ˈlī-təs 
plural encephalitides
in-ˌse-fə-ˈli-tə-ˌdēz
: inflammation of the brain that is caused especially by infection with a virus (such as herpes simplex or West Nile virus) or less commonly by bacterial or fungal infection or autoimmune reaction
Note: Encephalitis may be asymptomatic or present with mild to severe symptoms (such as fever, headache, confusion, seizures, or loss of consciousness) sometimes progressing to coma or death.
Examples of encephalitis in a Sentence
Recent Examples on the Web
Serious complications include pneumonia and encephalitis.
—
Greg Norman, FOXNews.com, 9 July 2025
About 1 in 150 people who are infected develop a severe illness affecting the central nervous system, such as encephalitis — the inflammation of the brain — or meningitis — inflammation of the membranes that surround the brain and spinal cord.
—Brandi D. Addison, Austin American Statesman, 2 June 2025
Inflammation in the brain About one in 1,000 children who contract measles will also develop encephalitis, or inflammation of the brain tissue, which can result in permanent damage.
—Emily Baumgaertner Nunn, New York Times, 4 Apr. 2025
An orangutan at the Little Rock Zoo died earlier this week of encephalitis, the zoo said in a news release.
—Harley Walls, Arkansas Online, 28 June 2025
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Greg Norman, FOXNews.com, 9 July 2025
About 1 in 150 people who are infected develop a severe illness affecting the central nervous system, such as encephalitis — the inflammation of the brain — or meningitis — inflammation of the membranes that surround the brain and spinal cord.
—Brandi D. Addison, Austin American Statesman, 2 June 2025
Inflammation in the brain About one in 1,000 children who contract measles will also develop encephalitis, or inflammation of the brain tissue, which can result in permanent damage.
—Emily Baumgaertner Nunn, New York Times, 4 Apr. 2025
An orangutan at the Little Rock Zoo died earlier this week of encephalitis, the zoo said in a news release.
—Harley Walls, Arkansas Online, 28 June 2025
See All Example Sentences for encephalitis
Cite this Entry
“Encephalitis.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/encephalitis. Accessed 25 Jul. 2025.
Copy CitationKids Definition
encephalitis
noun
en·ceph·a·li·tis
in-ˌsef-ə-ˈlīt-əs
(ˌ)en-
: inflammation of the brain
also
: a disease marked by encephalitis
Medical Definition
encephalitis
noun
en·ceph·a·li·tis
in-ˌsef-ə-ˈlīt-əs
plural encephalitides
-ˈlit-ə-ˌdēz
: inflammation of the brain that is caused especially by infection with a virus (such as herpes simplex, varicella zoster, or West Nile virus) or less commonly by bacterial or fungal infection or autoimmune reaction
Note: Encephalitis may be asymptomatic or present with mild to severe symptoms (such as fever, headache, confusion, seizures, or loss of consciousness) sometimes progressing to coma or death.
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