In the past twelve months, we have become acutely aware of the ways in which diseases are the products of our relationship with the natural world, by way of disease transmission between animals and humans. This process is called zoonosis, and has been identified by some commentators as 'a word of the future, destined for heavy use in the twenty-first century'. However, zoonosis is also a word of the past, whose theories and structure began to formulate 120 years ago, as the world froze in the face of another deadly pandemic: plague.  As we will hear in this episode, with the help of Dr Christos Lynteris of St Andrew's University, this third global pandemic of plague began the process of formulating epidemiological theories of zoonosis, the legacies of which still echo more than a century on.