An acute inflammatory disease of the brain caused by direct viral invasion of the herpes simplex virus. Herpes encephalitis produces swelling of the brain tissues and small hemorrhages throughout the brain’s hemispheres, the brain stem, cerebellum, and sometimes the spinal cord. When the brain is directly invaded by the herpes virus, nerve tissue is destroyed. Symptoms may include fever, fatigue, vomiting, confusion, delirium, and a stiff neck and back. Repeated seizures occurring during the early stages of infection are characteristic of herpes encephalitis, as differentiated from bacterial and other viral forms of the disease. There may also be signs of brain dysfunction, including altered consciousness, personality changes, and partial paralysis.