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The world has become more complex. The convergence of people, animals, and the environment has created a new dynamic characterized by a profound and unprecedented interdependence in which the health of all three domains is inextricably linked. This is significant for public health and, especially, for infectious diseases. Over the last three decades, approximately 75% of new emerging human diseases have been zoonotic (diseases that are transmitted from or through animals to humans).1 The human-animal interface is expanding, accelerating, and becoming more consequential. At the same time, we have permanently altered a significant portion of our ecosystems and have created a new ecological milieu that is changing the conditions of our human-animal interface, the conditions for microbial adaptation and the emergence and re-emergence of infectious diseases worldwide. Our challenge is to create and implement a transformational model based on a holistic and integrated approach that addresses our health threats with a new emphasis on prevention, and addresses problems closer to their origin, often within the animal and environmental domains. This approach is the essence of the One Health concept.


One Health can be defined as the collaborative effort of multiple disciplines—working locally, nationally, and globally to attain optimal health for people, other animals, and the environment.2 The scope of One Health is impressive, broad, and growing. Much of the recent focus on One Health has been limited to emerging infectious diseases, yet the concept clearly embraces ecosystem health, social sciences, biodiversity, ecology, chronic diseases, and more. Although there may be other variations of the definition of One Health, there is broad consensus that a new framework for preventing diseases is essential for our future, rather than accepting the status quo which is a more reactive response.

Figure 84-1 is a simple Venn diagram depicting the three domains of One Health and their close inter-relationship. The size and influence of each domain is relative and variable depending on the events within each domain. Each domain, progressively and consistently, influences the health within the other spheres. The relationship among these domains is analogous to Newton’s Third Law of Motion. Because of the intense interconnectivity of animal, human, and environmental risk factors, for almost every action in one domain, there is an equal and opposite reaction in the others.


Dynamics of One Health domains; Newton’s third law of motion: for every action, there is an equal and opposite reaction.


The concept of One Health is not new and the idea can be traced to ancient history. Early societies learned that basic sanitation (clean water and removal of waste and vermin) was critical to the population’s health. From Greek mythology, Apollo’s son Asclepius was tasked by the gods to care for ...

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