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

Before vaccination was widely available, about 1,000 people developed chronic disability from acute encephalitis caused by measles annually, according to the CDC. — Jen Christensen, CNN Money, 16 Sep. 2026

Measles can be especially dangerous for young children and pregnant women and can lead to severe complications, such as pneumonia, encephalitis and death. — Katie Wiseman, Louisville Courier Journal, 11 Sep. 2026

The doctor said his colleagues are struggling to treat infected children who often arrive at the hospital with serious complications like pneumonia, diarrhea and encephalitis, or brain swelling. — Julhas Alam, Los Angeles Times, 9 Sep. 2026

Severe infections can lead to serious health complications such as pneumonia, encephalitis or meningitis, the Cleveland Clinic said. — Hali Smith, Idaho Statesman, 8 Sep. 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