A disease that appears as epidemics from time to time, especially in the spring. The virus attacks chiefly the basal ganglia and cerebellum of the brain and the brain stem. The disease begins with fever and drowsiness, which after a week or so may pass to complete lethargy, accompanied by paralysis of varying degrees, even to unconsciousness. There is no specific treatment and the disease can run a course of several months.
Epidemic encephalitis, popularly known as sleeping sickness, was first described in Vienna in 1917; by 1918 the epidemic had reached Germany and the UK, and by 1920 the whole world. There was another peak incidence in 1924, but if the virus that is presumed to have been the etiologic agent now exists at all, it is not known to have produced an epidemic since 1927.