Encephalitis lethargica and the influenza virus. II. The influenza pandemic of 1918/19 and encephalitis lethargica: epidemiology and symptoms.

This is the first of two papers which critically examine the relationship between the 1918/19 influenza pandemic and encephalitis lethargica (EL). The role of influenza in the etiology of EL was vigorously debated until 1924. It is notable, however, that the unitarian camp were largely reactive in their argumentation; while the influenza skeptics provided detail descriptions of EL and the features they argued to be unique or at least unusual, influenza supporters focused on sequentially refuting the evidence of their opponents. The impression which emerges from this debate is that the individual features identified by the skeptics were not absolutely pathognomic for EL, but, on the other hand, their combination in one disorder had not previously been described for any other disease.