Demystifying a buzzword: Use of the term "human-animal-interface" in One Health oriented research based on a literature review and expert interviews

As of today, 75% of infectious human diseases are caused by zoonotic pathogens, which use the interface between humans and animal species to cross. Due to this ability, zoonoses affect more than just one health sector and the effective control is a matter of the One Health concept. One defining feature of this concept is the "human-animal-interface". However, even though the term is ubiquitously used in the field of infectious disease research, a clear definition of the term is lacking, leading to a rather nebulous understanding of what this interface really encompasses. Based on this observation, this study aimed to analyze the use of the term "human-animal-interface" in scientific literature to identify patterns and categories facilitating a scientific categorization. A systematic literature search of two electronic databases was performed complemented by interviews with health experts in the field of zoonoses/One Health conducted between March 2019 and May 2021. From identified publications, keywords and interface descriptions were extracted and categorized. Interviews followed a questioning route, were audio recorded, transcribed, and qualitative content was inductively categorized. Findings are based on 208 publications and 27 expert interviews. "Transmission" and "zoonosis" were the most frequent literature-based keywords, while the interviewees clearly favored "interface" followed by "contact". Seven categories of contact interfaces were inductively derived: direct contact (physical contact), consumption of animal products, use of animal products (blood transfusion, skin), contact with animal products (blood, secretion, meat), indirect contact (dust, inhalation, droplets), environmental contact (same surface or food), vector contact). Precise descriptions of the interfaces varied greatly depending on the pathogen domain (bacterial, viral, fungal). Specific patterns could be identified that were consistent between the literature and experts. The study results showed a general concordance in defining and describing the human-animal-interface indicating a general understanding of the term. However, studies on a larger scale are recommended (e.g. systematic review) to allow a more thorough view of the understanding and definition of the human-animal-interface.