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
About 1 in 1,000 children who get sick develop encephalitis, or brain inflammation, which can lead to deafness, convulsions and intellectual disabilities.
—
Eduardo Cuevas, USA Today, 14 Oct. 2025
Beckett Wear temporarily lost his ability to walk after two bouts of acute necrotizing encephalitis.
—Erika Edwards, NBC news, 25 Sep. 2025
Along with a high fever, cough, and runny nose, measles also carries a risk of pneumonia and encephalitis (swelling of the brain), which can cause hearing loss, cognitive disabilities and death.
—Cara Lynn Shultz, PEOPLE, 25 Sep. 2025
In rare serious cases, the virus invades the nervous system, causing meningitis, encephalitis (swelling of the brain), paralysis or death.
—Khloe Quill, FOXNews.com, 15 Sep. 2025
See All Example Sentences for encephalitis
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Eduardo Cuevas, USA Today, 14 Oct. 2025
Beckett Wear temporarily lost his ability to walk after two bouts of acute necrotizing encephalitis.
—Erika Edwards, NBC news, 25 Sep. 2025
Along with a high fever, cough, and runny nose, measles also carries a risk of pneumonia and encephalitis (swelling of the brain), which can cause hearing loss, cognitive disabilities and death.
—Cara Lynn Shultz, PEOPLE, 25 Sep. 2025
In rare serious cases, the virus invades the nervous system, causing meningitis, encephalitis (swelling of the brain), paralysis or death.
—Khloe Quill, FOXNews.com, 15 Sep. 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 31 Oct. 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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