Emergence and Spread Risk of Highly Pathogenic Avian Influenza in Seabird Species of New Caledonia

The ongoing expansion of Highly The ongoing expansion of Highly Pathogenic Avian Influenza Virus (HPAIV) H5N1 is driving unprecedented wildlife mortality and raising global health concerns. To date, Oceania remains the last region free of HPAIV, offering a critical opportunity to anticipate and mitigate future emergence. Here, we assess the risk of HPAIV introduction and spread within seabird communities of New Caledonia, a key biodiversity hotspot of the South Pacific located along major transoceanic migratory routes. We compiled a comprehensive list of seabird species previously exposed to HPAIV and evaluated their likelihood of occurrence in New Caledonia using literature and global biodiversity databases. Species were classified as breeding or non-breeding, and their potential roles in virus dynamics were quantified using trait-based indices. Additionally, seabird migratory connectivity between New Caledonia and surrounding regions was estimated. Among 71 retained seabird species, several long-distance migrant species—particularly within Procellariidae and Charadriiformes—emerged as potential high-risk vectors, although often with low probability of occurrence locally. In contrast, highly colonial breeding species, including Thalasseus bergii and Fregata minor, showed the greatest potential to amplify local transmission. Network analyses revealed that the strongest ecological connections occur with nearby regions not yet affected by HPAIV, whereas links to infected areas involve distances > 2000 km, potentially constraining virus emergence in the South Pacific. Our results identify priority species and critical knowledge gaps, providing a framework to guide targeted surveillance and proactive management strategies in the South Pacific.