It's not always clear what causes encephalitis. When a cause is found, it's usually an infection or a problem with the immune system (the body's natural defences).
Encephalitis is inflammation of the brain, usually caused by an infection. It's a rare but serious condition.
Encephalitis may start off with flu-like symptoms. More serious symptoms include confusion, seizures, difficulty speaking and feeling weak.
Encephalitis needs urgent treatment in hospital. Depending on the cause, treatment may include antiviral medicines, steroids or antibiotics.
Some of the infections that cause encephalitis can be prevented with vaccines, such as the MMR and Japanese encephalitis vaccines.
Page last reviewed: 06/12/2016
Next review due: 06/12/2019