Herpes simplex virus encephalitis (HSE) is caused by the infection of the central nervous system by Herpes simplex virus (HSV) that could have a devastating clinical course and a potentially fatal outcome particularly with delay or lack of treatment. HSV often involves the frontal and temporal lobes, usually asymmetrically, resulting in personality changes, cognitive impairment, aphasia, seizures, and focal weakness. The disease is herpes simplex encephalitis (MONDO_0012521). Also known as: Encephalitis, Herpes Simplex, HSE, HSV encephalitis, HSVE, Herpes simplex meningo-encephalitis, Herpes simplex neuroinvasion, Simplexvirus caused infectious encephalitis, Simplexvirus infectious encephalitis.