In 1917, at the height of the Great War, a new and mysterious disease emerged into the world, before vanishing a few years later. Although it was to prove less destructive than the 1918 influenza pandemic which occured at around the same time, the new outbreak had a persistent legacy: some of the victims of the disease remained disabled decades later.

The new syndrome was first reported by Constantin von Economo, a neurologist in Vienna. He dubbed the disease ‘encephalitis lethargica’, after