Encephalitis is an inflammation of the brain that is usually caused by a direct viral infection. Common causes include herpes simplex virus, enteroviruses, and mosquito-borne viruses. Symptoms include fever, headache, seizures, confusion, drowsiness, and loss of consciousness. Diagnostic tests include brain imaging, spinal taps, and tests of blood, urine, and throat samples to identify the infectious agent. Treatment focuses on relieving swelling with corticosteroids, treating the underlying infection, and providing supportive care. Those who survive may require long-term physical, occupational, and speech therapy to recover lost functions.