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
In September 1879, the girl died of viral encephalitis — presumed to have been transmitted by a mosquito — just weeks before her 13th birthday.
—
Camila Pedrosa, Sacbee.com, 31 Mar. 2026
Roughly 1 in 20 children with measles develops pneumonia, and about 1 out of every 1,000 children who have measles infections also will have encephalitis.
—Kristen Jordan Shamus, Freep.com, 19 Mar. 2026
Other complications include meningitis (inflammation of the membrane surrounding the brain and spinal cord), encephalitis (inflammation of the brain), inflammation of the pancreas, and hearing loss.
—Emily Kay Votruba, EverydayHealth.com, 16 Mar. 2026
People who recover from measles can experience complications such as pneumonia, which can lead to death, or encephalitis, which can later lead to deafness or intellectual disabilities from the brain swelling.
—Andrea Uhlig, The Conversation, 12 Mar. 2026
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Camila Pedrosa, Sacbee.com, 31 Mar. 2026
Roughly 1 in 20 children with measles develops pneumonia, and about 1 out of every 1,000 children who have measles infections also will have encephalitis.
—Kristen Jordan Shamus, Freep.com, 19 Mar. 2026
Other complications include meningitis (inflammation of the membrane surrounding the brain and spinal cord), encephalitis (inflammation of the brain), inflammation of the pancreas, and hearing loss.
—Emily Kay Votruba, EverydayHealth.com, 16 Mar. 2026
People who recover from measles can experience complications such as pneumonia, which can lead to death, or encephalitis, which can later lead to deafness or intellectual disabilities from the brain swelling.
—Andrea Uhlig, The Conversation, 12 Mar. 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 4 Apr. 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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