The pandemic of von Economo's disease which began in January 1917 prec
eded that of influenza of 1918-1919 by more than a year. Though it has
been customary to link the two it seems unlikely that the latter was
responsible for the former as has been proposed. It has been assumed t
hat von Economo's disease (ED) was caused by a virus; but in fact the
etiology is in question as no virus has yet been transmitted to experi
mental animals or cells in culture. However, the presence of oligoclon
al IgG bands in the CSF of suspected cases and the finding of chronic
active lesions in the brain tissue at autopsy suggests a viral etiolog
y. Occasional, sporadic presumed cases of the disease have been report
ed within the last 25 years. Encephalitides due to established neurotr
opic viruses or to other viruses that may on occasion invade the CNS o
nly rarely produce parkinsonism, and when they do it differs from that
seen in ED. The present report reviews the overall concept of a viral
etiology of Parkinson's disease with particular reference to von Econ
omo's disease.