Encephalitis (en-sef-uh-LIE-tis) is inflammation of the brain. There are several causes, but the most common is viral infection.
Encephalitis often causes only mild flu-like signs and symptoms — such as a fever or headache — or no symptoms at all. Sometimes the flu-like symptoms are more severe. Encephalitis can also cause confused thinking, seizures, or problems with senses or movement.