Cellosaurus Disease Terminology Viral Encephalitis Herpes Simplex Encephalitis C0276226 Herpes Simplex Encephalitis Disease or Syndrome Herpes Simplex Encephalitis Cellosaurus C84762 A serious viral disorder characterized by infection of the brain by herpes simplex virus type 1 or 2. Herpes simplex virus type 1 affects adults, whereas herpes simplex virus type 2 affects newborns. Signs and symptoms include fever, headaches, vomiting, seizures and psychiatric manifestations.