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
Mosquitoes can transmit Zika, dengue fever, malaria and encephalitis, to name a few illnesses—all of which are harmful to human health and can kill.
—
Jackie Flynn Mogensen, Scientific American, 15 Jan. 2026
Advertisement Paranoia Abrupt behavior and personality changes can be the result of conditions like autoimmune encephalitis, frontotemporal dementia, or other cognitive disorders.
—Angela Haupt, Time, 15 Jan. 2026
Bernthal and Angle's daughter faced a dangerous health scare in 2017 when she was diagnosed with encephalitis and fell into a coma.
—Caroline Blair, PEOPLE, 14 Jan. 2026
Measles is a highly contagious respiratory virus that can lead to severe health complications including pneumonia, encephalitis and death, particularly in young children.
—Gillian Stawiszynski, Cincinnati Enquirer, 14 Jan. 2026
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Jackie Flynn Mogensen, Scientific American, 15 Jan. 2026
Advertisement Paranoia Abrupt behavior and personality changes can be the result of conditions like autoimmune encephalitis, frontotemporal dementia, or other cognitive disorders.
—Angela Haupt, Time, 15 Jan. 2026
Bernthal and Angle's daughter faced a dangerous health scare in 2017 when she was diagnosed with encephalitis and fell into a coma.
—Caroline Blair, PEOPLE, 14 Jan. 2026
Measles is a highly contagious respiratory virus that can lead to severe health complications including pneumonia, encephalitis and death, particularly in young children.
—Gillian Stawiszynski, Cincinnati Enquirer, 14 Jan. 2026
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 Jan. 2026.
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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