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
Unvaccinated children under the age of 5 have an elevated risk of experiencing dangerous complications due to measles, including pneumonia, encephalitis (brain inflammation), loss of sight or hearing and death, per the CDC.
—
Caroline C. Boyle, USA Today, 14 Apr. 2025
Those in the high-risk groups could also develop ear infections, blindness, encephalitis — a brain swelling infection — and respiratory illnesses, including pneumonia, bronchiectasis, and laryngitis.
—Monica Cull, Discover Magazine, 7 Apr. 2025
One in five unvaccinated people with measles will be hospitalized, 1 in 20 children with measles will develop pneumonia, and 1 in 1,000 children with measles will develop encephalitis, or swelling of the brain.
—Neha Mukherjee, CNN, 19 Mar. 2025
The most common symptoms are high fiver, cough, conjunctivitis and rash, with serious complications including ear infections, diarrhea, pneumonia and encephalitis.
—Matt Leclercq, Fort Worth Star-Telegram, 8 Apr. 2025
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Caroline C. Boyle, USA Today, 14 Apr. 2025
Those in the high-risk groups could also develop ear infections, blindness, encephalitis — a brain swelling infection — and respiratory illnesses, including pneumonia, bronchiectasis, and laryngitis.
—Monica Cull, Discover Magazine, 7 Apr. 2025
One in five unvaccinated people with measles will be hospitalized, 1 in 20 children with measles will develop pneumonia, and 1 in 1,000 children with measles will develop encephalitis, or swelling of the brain.
—Neha Mukherjee, CNN, 19 Mar. 2025
The most common symptoms are high fiver, cough, conjunctivitis and rash, with serious complications including ear infections, diarrhea, pneumonia and encephalitis.
—Matt Leclercq, Fort Worth Star-Telegram, 8 Apr. 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 3 May. 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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