Alien mammal introductions can reshape global viral sharing networks

Abstract Alien mammals introduced beyond their native distribution ranges can bring novel pathogens into the colonised communities and alter pathogen transmission dynamics. Past studies identified immunological and ecological drivers of cross-species viral transmission, but this knowledge has rarely been applied to alien species, leading to an underestimation of their role in disease emergence. Here we predict the viral sharing network resulting from the establishment of 67 alien mammals introduced globally in the last 50 years, using a trait- and phylogeny-informed viral sharing model. We show that the introduction of alien mammals can result, on average, in six novel viral sharing events per introduction (95% CI = 5.03–6.98), potentially reshaping the viral sharing networks of local communities. Phylogenetic relatedness emerged as the strongest predictor of viral sharing between alien and native species, with additional contributions from trait-based, dietary, and habitat similarities. Predicted viral sharing was concentrated in the Global North, reflecting potential geographic biases in both introduction records and viral surveillance. Our approach provides a quantitative tool to estimate viral hazards driven by established alien species that can be used to support risk assessment frameworks and international policy on biological invasions.