A history of One Health.

One Health is not a new concept. It can be demonstrated that its origins and development literally run the gamut from A to Z, that is to say, from Aristotle to Zoobiquity. Indeed, the consequences of the interaction that occurs between ecosystems, animals and people have shaped, and continue to shape, the course of human events and history. A reasoned and evidence-based assessment of the history of One Health must first be founded on an agreed definition of the term, but, given the many disciplines and sciences involved, finding such a definition is no easy task. Furthermore, there is an extensive and growing list of visionary individuals who have, over the centuries, attempted to promote awareness and advance the conceptto improve the management of the risks and consequences that arise at the interface between animal, human and ecosystem health. The One Health ideas of the 21st Century constitute a re-conceptualisation of health management in response to the accelerating environmental changes of the past 100 years, changes that are associated with the parallel exponential growth and concentration of the global human population. Consequently, the concept of One Health must recognise the constantly evolving relationship between animals and humans and the planet they share.