Wild Birds Affected by Highly Pathogenic Avian Influenza A ( H5N1 ) Worldwide: Epidemiological Insights Into the Recent Panzootic

Abstract

In recent years, especially as a consequence of global change, several emerging pathogens have caused alarming effects in wild species. One of these pathogens, the Highly Pathogenic Avian Influenza A (H5N1), is causing global mortalities in animals with an increasing risk to humans. Wild birds play a key role in viral transmission and spread. Using the distribution ranges of wild bird species reported as infected, we mapped global risk areas for viral spread and analyzed the spatio-temporal evolution of H5N1 from January 2017 to March 2025. We also examined the overlap between the mapped risk areas and positive cases occurring in wild birds and poultry over this period to evaluate whether these cases align with the risk areas previously identified. Finally, we evaluated whether ecological traits of wild birds, such as gregariousness, tolerance of anthropic habitats, migratory behavior, and trophic level, are associated with the viral infection. From 2017 to September 2020, the H5N1 virus high-risk areas and cases in wild birds and poultry were few and mainly limited to Asia and Europe. From October 2020 to March 2025, the rise in H5N1 cases led to rapid expansion of high-risk areas for virus circulation and spread to almost the entire world. The increase in cases occurred within predicted high-risk areas for both wild birds and poultry. The wild bird species most at risk of contracting the viral infection were those that are gregarious, tolerant of anthropic habitats, are non-migratory, and occupy the upper trophic level. Our findings provide insights that could enhance surveillance and conservation efforts aimed at mitigating the adverse impacts of H5N1 virus. These efforts can be optimized by prioritizing high-risk regions and species identified as particularly susceptible to H5N1.