The First World War as a super-spreading event not only increased transmission of well-known diseases, it also ensured that conditions were ripe for the emergence of new infections. In 1915 military doctors on the Western Front became perplexed by patients who were suffering from a new, unfathomable illness. These patients displayed a wide variety of symptoms, including fever, rashes, headaches, dizziness, excruciating pain behind the eyes and severe weakness, accompanied by sore muscles, joint, back and shin pain. Initially diagnosed as PUO (pyrexia of unknown origin), the illness affected Allied forces and those of the Central Powers. There were at least 800,000 cases within Allied troops on the Western Front, eventually accounting for one-fifth of field hospital admissions.
Characterised by a sudden onset of symptoms, this illness, which became known…