An epidemic caused people to fall asleep for months – we still don’t know why

One hundred years ago, across the world, people were falling asleep uncontrollably.

Not from a hard day’s work or a late night, but a disease known as ‘sleepy sickness’.

Victims fell into a slumber so deep that those who caught it often didn’t wake for weeks, or even months, at a time. It was also deadly, killing 30 to 40% of those affected, usually from respiratory failure.

An epidemic, it emerged from northern France in 1916...