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
Complications of the virus can include inflammation of the brain, or encephalitis; inflammation of the lining of the brain and spinal cord, or meningitis; and inflammation of the brain and its surrounding membrane, Johns Hopkins Medicine said.
—
Don Sweeney, Sacbee.com, 11 May 2026
Sigler described the condition as encephalitis.
—Angel Saunders, PEOPLE, 11 May 2026
Other complications include encephalitis and subacute sclerosing panencephalitis (SSPE), which officials say is a rare but fatal progressive brain disease that develops years after infection.
—John Ramos, CBS News, 15 Apr. 2026
The Directorate General of Health Services said unvaccinated children or those who have not completed the two-dose measles schedule face the greatest risk and that malnourished children are particularly prone to severe complications such as pneumonia and encephalitis.
—Reuters, NBC news, 2 Apr. 2026
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Don Sweeney, Sacbee.com, 11 May 2026
Sigler described the condition as encephalitis.
—Angel Saunders, PEOPLE, 11 May 2026
Other complications include encephalitis and subacute sclerosing panencephalitis (SSPE), which officials say is a rare but fatal progressive brain disease that develops years after infection.
—John Ramos, CBS News, 15 Apr. 2026
The Directorate General of Health Services said unvaccinated children or those who have not completed the two-dose measles schedule face the greatest risk and that malnourished children are particularly prone to severe complications such as pneumonia and encephalitis.
—Reuters, NBC news, 2 Apr. 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 21 May. 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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