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West Nile virus (WNV) is a globally widespread arthropod-borne virus that poses a significant public health concern. Mosquitoes transmit the virus in an enzootic cycle among birds, which act as reservoirs. Climate plays a crucial role in these outbreaks as mosquitoes are highly influenced by climatic conditions, and bird migrations are also affected by weather patterns. Consequently, changes in climate can potentially impact the occurrence of WNV outbreaks. We used biogeographic modelling based on machine learning algorithms and fuzzy logic to analyse and evaluate separately the risk of WNV outbreaks in two different biogeographic regions, the Afrotropical and the Western Palaearctic region. By employing fuzzy logic tools, we constructed a comprehensive risk model that integrates the Afro-Palaearctic system as a unified operational unit for WNV spread. This innovative approach recognizes the Afro-Palaearctic region as a pathogeographic system, characterized by biannual connections facilitated by billions of migratory bird reservoirs carrying the disease. Subsequently, we forecasted the effects of different climate change scenarios on the spread of WNV in the Afro-Palaearctic system for the years 2040 and 2070. Our findings revealed an increasing epidemic and epizootic risk south of the Sahara. However, the area where an upsurge in risk was forecasted the most lies within Europe, with the anticipation of risk expansion into regions presently situated beyond the virus' distribution range, including central and northern Europe. Gaining insight into the risk within the Afro-Palaearctic system is crucial for establishing coordinated and international One Health surveillance efforts. This becomes particularly relevant in the face of ongoing climate change, which disrupts the ecological equilibrium among vectors, reservoirs, and human populations. We show that the application of biogeographical tools to assess risk of infectious disease, i.e. pathogeography, is a promising

West Nile virus (WNV) is a globally significant vector-borne disease that is primarily transmitted between birds and mosquitoes. Recently, there has been an increase in WNV in southern Europe, with new cases reported in more northern regions. Bird migration plays a crucial role in the introduction of WNV in distant areas. To better understand and address this complex issue, we adopted a One Health approach, integrating clinical, zoological, and ecological data. We analyzed the role of migratory birds in the Palaearctic-African region in the spread of WNV across Africa and Europe. We categorized bird species into breeding and wintering chorotypes based on their distribution during the breeding season in the Western Palaearctic and the wintering season in the Afrotropical region, respectively. By linking these chorotypes to the occurrence of WNV outbreaks in both continents throughout the annual bird migration cycle, we investigated the relationship between migratory patterns and virus spread. We demonstrate that WNV-risk areas are interconnected through the migration of birds. We identified a total of 61 species that potentially contribute to the intercontinental spread of the virus or its variants, as well as pinpointed high-risk areas for future outbreaks. This interdisciplinary approach, which considers the interconnectedness of animals, humans, and ecosystems, represents a pioneering effort to establish connections between zoonotic diseases across continents. The findings of our study can aid in anticipating the arrival of new WNV strains and predicting the occurrence of other re-emerging diseases. By incorporating various disciplines, we can enhance our understanding of these complex dynamics and provide valuable insights for proactive and comprehensive disease management strategies.