Encephalitis is an acute inflammation of the brain, usually caused by a viral infection or the immune system attacking brain tissue. It affects 7.4 cases per 100,000 people annually in Western countries. Common causes include herpes simplex virus, rabies virus, and childhood infections. Symptoms include fever, headaches, drowsiness, personality changes, and seizures. Diagnosis involves medical history, physical exam, imaging tests, and spinal tap. Treatment focuses on antiviral drugs, rest, hydration, and rehabilitation to address complications like weakness and memory problems.