Infectious disease emergence increasingly reflects interactions among ecological change, human activity, and global connectivity. This article examines infectious disease ecology as a socio-ecological system in which biodiversity dynamics, land-use transformation, climate variability, and mobility networks collectively shape pathogen circulation. Rather than viewing outbreaks as isolated biological events, the analysis situates disease risk within integrated “people–nature” systems where environmental disturbance, species composition, and economic activity reorganize patterns of contact among hosts, vectors, and pathogens. The article explores several interacting drivers of disease emergence, including habitat fragmentation, agricultural intensification, wildlife trade, global transport networks, and climatic variability. These processes reshape ecological interfaces and alter opportunities for spillover, demonstrating that transmission risk often arises not from the presence of pathogens alone but from the changing configuration of ecological and social relationships. Particular attention is given to how biodiversity change, community composition, and environmental pressures interact across landscapes to produce context-dependent outcomes. Beyond ecological mechanisms, the analysis also considers the economic consequences of disease emergence and the role of preventive investments such as environmental monitoring, wildlife surveillance, and early detection systems. In this context, the article evaluates the One Health paradigm as an institutional framework designed to integrate human, animal, and ecosystem health governance across sectors and scales. By interpreting infectious diseases through a systems lens, the article argues that disease emergence should be understood as a signal of broader transformations within ecological and social networks. Understanding these dynamics requires sustained attention to the relationships linking biodiversity, environmental change, and human development in an increasingly interconnected world. Rather than offering a single causal explanation, infectious disease ecology invites continued observation of the evolving interactions through which health, ecosystems, and societies remain intertwined.