Integrating host competence and vector distribution to predict current and latent hotspots of West Nile virus hazard

West Nile virus (WNV) is a mosquito-borne zoonotic pathogen with expanding distribution and recurrent outbreaks in Europe and the Americas. WNV transmission depends on interactions between competent avian hosts and mosquito vectors, but empirical data on host competence remain narrow, limiting large-scale assessments of viral hazard. Here, we compile viremia data from experimental infections of birds and develop a trait-based, phylogenetically informed model to predict global avian host competence. We integrate predictions with the habitat distribution of competent Culex vectors to estimate WNV hazard across the Americas and Europe. Our model identified over 4900 avian species as potentially competent hosts for WNV. The Mediterranean Basin and eastern North America showed high host richness-co-occurrence of several predicted host species-and high suitability for Culex vectors. Conversely, several tropical and subtropical regions had high host richness but limited vector suitability at present. These areas represent 'latent' hotspots of hazard, i.e. areas with high potential for future WNV emergence under environmental change. Our results refine the understanding of where WNV transmission is most likely to occur at present and highlight regions at risk of future emergence. This approach can inform risk mapping, surveillance efforts and targeted public health interventions.