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.

encephalitic

in-ˌse-fə-ˈli-tik 

adjective

Examples of encephalitis in a Sentence

Recent Examples on the Web

In these cases, the virus affects the brain or nervous system and can cause encephalitis or meningitis, which can result in an infection of the brain or surrounding tissue. — Karen Garcia, Los Angeles Times, 8 July 2026

Besides being nuisances, many types carry diseases including West Nile virus, encephalitis, and canine heartworm. — Arricca Elin Sansone, Southern Living, 3 July 2026

In rare instances, the disease can affect the central nervous system, causing encephalitis or meningitis that may require hospitalization and can result in death. — Reeti Malhotra july 2, Sacbee.com, 2 July 2026

These high-priority henipaviruses, originating from fruit bats, spread to humans causing severe pneumonia and encephalitis. — William A. Haseltine, Forbes.com, 2 July 2026

Word History

First Known Use

1843, in the meaning defined above

Phrases Containing encephalitis

• Eastern equine encephalitis
• equine encephalitis
• Powassan encephalitis
• Saint Louis encephalitis
• St. Louis encephalitis
• Venezuelan equine encephalitis
• Western equine encephalitis
• West Nile encephalitis

Rhymes for encephalitis

• alveolitis
• bronchiolitis
• caenorhabditis
• cholecystitis
• endometritis
• endophthalmitis
• folliculitis
• periostitis
• peritonitis
• polyneuritis
• thrombophlebitis
• adenitis

Kids 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.

encephalitic

-ˈlit-ik 

adjective