Molecular and ecological determinants of viral emergence in tropical regions: a One Health perspective integrating host–pathogen interactions, immune dysregulation, translational diagnostics, and epidemiological surveillance

Background Emerging viral diseases continue to represent a major threat to global public health, particularly in tropical regions where complex interactions between biodiversity, ecological disruption, climate change and socioeconomic factors create favorable conditions for zoonotic viral emergence. Current evidence suggests that tropical ecosystems offer ecological conditions where multiple drivers converge to improve opportunities for pathogen spillover and subsequent transmission, rather than simply attributing the emergence of viruses to tropical environments. Identifying these interplay determinants in a One Health setting is key to improving surveillance and pandemic preparedness. Main body This structured narrative review integrates current evidence on the ecological, molecular, immunological, and translational drivers of viral emergence in tropical settings. Ecological factors include host-reservoir diversity, vector ecology, climate change, land-use change, forest fragmentation, agricultural intensification, and increased interface between people and animals. The molecular factors include the adaptive evolution of RNA viruses, receptor-binding plasticity, and immune-evasion strategies that make cross-species transmission possible. The review also covers dysregulation of innate immunity, interference with interferon activity, and cytokine storm and discusses the importance of the roles of the adaptive immune memory and cross-protective immunity in the outcome of diseases. The readers will learn about recent developments in genomic surveillance, next-generation sequencing, CRISPR-based diagnostic tests, and other point-of-care technologies discussed in a One Health context. Finally, we introduce the concept of the Tropical Viral Emergence Risk Index (TVERI) as a means of integrating contextual ecological, molecular, and immunological information to help with risk assessment. Conclusion The emergence of viruses is the result of complex, non-linear interactions between ecological change, viral evolution, host immunity and environmental pressures. To improve predictive surveillance in tropical areas, integrated One Health approaches that combine ecological monitoring, molecular epidemiology and accessible diagnostic technologies are needed. Future validation of conceptual frameworks such as TVERI could enable more comprehensive assessments of viral emergence risk and support evidence-based preparedness strategies.