Experimenting on the past: The enigma of von Economo's encephalitis lethargica

Encephalitis lethargica (EL) was a complex and mysterious disease that appe ared around the same time as the great influenza pandemic of 1918. The cont emporaneous relationship of the 2 diseases led to speculation that they wer e causally related. Contemporary and subsequent observers conjectured that the influenza virus directly responsible for the deaths of more than 20 mil lion people, might also have been the cause of EL. A review of the extensiv e literature by observers of the EL epidemic suggests that most contemporar y clinicians, epidemiologists. and pathologists rejected the theory that th e 1918 influenza virus was directly responsible for EL. Disappearance of th e acute form of EL during the 1920s has precluded direct study of this enti ty. However, modern molecular biology techniques have made it possible to e xamine archival tissue samples from victims of the 1918 pandemic in order t o detect and study the genetic structure of the killer virus. Similarly. ti ssue samples from EL victims can now be examined for evidence of infection by the 1918 influenza virus.