While the plague of Provence is the most studied outbreak of the disease in early modern Europe, there is little in the extensive historiography on this topic about fears of the cross-species transmission of disease which re-emerged in the early eighteenth century because of events in southwestern France. Concerns about the interplay between cattle murrains and human plague resurfaced in the early eighteenth century because the plague of Provence followed an outbreak of cattle disease which swept across Europe and killed tens of thousands of animals. This article focuses on the debate about the spread of contagious diseases between species which occurred in Britain during this time. Links between the health of animals and that of humans became objects of heated discussion especially following the issuing of the 1721 Quarantine Act, which was designed to prevent the plague currently ravaging southwestern France from taking hold in Britain. It then considers the different beliefs regarding contagion and the transmission of diseases between different species during the plague of Provence. While focusing on the richly documented and highly revealing discussions in early eighteenth-century Britain about the interplay between plague in cattle and plague in humans, it also utilises materials from earlier centuries to examine more fully how early modern populations understood the relationship between plague in humans and cattle murrains.