Evaluating one health: Are we demonstrating effectiveness?

•We conducted a literature review of One Health literature.•Standardized evaluations of One Health approaches are generally lacking.•An integrated framework can grow a strong evidence base to inform decision-making.

The perceived benefits of a One Health approach are largely hinged on increasing public health efficiency and cost effectiveness through a better understanding of disease risk-through shared control and detection efforts, and results that benefit human, animal and ecosystem health. However, there have been few efforts to identify and systematize One Health metrics to assess these perceived efficiencies. Though emphasis on the evaluation of One Health has increased, widely cited benefits of One Health approaches have mainly been based on modeled projections, rather than outcomes of implemented interventions. We conducted a review of One Health literature to determine the current status of One Health frameworks and case studies reporting One Health metrics. Of 1839 unique papers, only 7 reported quantitative outcomes; these assessments did not follow shared methodology and several reviewed only intermediate outcomes. For others, the effectiveness of One Health approaches was often assumed without supporting evidence or determined subjectively. The absence of a standardized framework to capture metrics across disciplines, even in a generic format, may hinder the more widespread adoption of One Health among stakeholders. We review possible outcome metrics suitable for the future evaluation of One Health, noting the relevance of cost outcomes to the three main disciplines associated with One Health.