However, the incidence of this disease has decreased dramatically in the United States following the nationwide measles immunization program. More males are affected than females, and the disease generally occurs in children and adolescents. Affected individuals generally succumb one to two years after diagnosis but some may survive for longer periods. SSPE begins slowly with subtle behavioral changes and mounting difficulty in school. As the disease progresses, behavior becomes bizarre and the person eventually develops dementia, stupor , coma , and finally death.
Physical signs are few until the disease is well advanced.