This essay surveys some of the most prominent metaphors used to characterize infectious diseases in eighteenth-century literature. These include military metaphors that portray the disease as the enemy; ‘othering’ metaphors that categorize infection as a foreign immigrant, import, or invader; and commercial metaphors that compare the circulation of a disease with the circulation of currency or commodities. Using Defoe’s Journal of the Plague Year as a test case, I demonstrate that multiple disease metaphors often operate within a single text, creating a more nuanced and complex portrait of infection than we might otherwise expect in this period. Ultimately, I argue that disease metaphors in eighteenth-century literature are almost always complicated and equivocal, with writers like Defoe drawing attention to the social and ethical meanings of an epidemic, and not just its terrifying destructive force.