The concept of health in One Health and some practical implications for research and education: what is One Health?

From a strict biological point of view, humans are just one species among other species, albeit one with very special capacities, characteristics, and skills. Among scientists, it is generally acknowledged that we share many features with other animal species, which are certainly relevant when the concepts of health and disease are discussed. The term 'One Health' is used in many different contexts and by people with varying backgrounds. However, there appears to be some confusion as to what the term really means, and it is used in a wide range of contexts, often including or bordering concepts such as infection biology, contagious diseases, zoonotic infections, evolutionary medicine, comparative medicine, and translational medicine. Without claiming to present the one and only true interpretation, we will argue for a wide approach using the 'umbrella' depiction developed by One Health Sweden. We argue that this one should, compared to other demarcations, be more useful to science. We will also analyze the concept of health on different levels: individual, population, and ecosystem health, and describe how these levels inherently influence each other for both humans and animals. Both these choices are normative and have practical consequences for research and education, a way of reasoning which we develop further in this paper. Finally, we conclude that the choice of term for the approach might be normative in deciding which disciplines or parts of disciplines that may be included.