A Nature study led by Louise H. Moncla traces the origins, introductions, and spread of H5N1 in the first 18 months of the North American epizootic, showing wild birds as the central vectors.

Wild birds, especially Anseriformes like ducks, geese, and swans, are identified as the primary drivers of the current outbreak in North America.

Eradication in wild reservoirs is unlikely; efforts should focus on reducing spillover risk and protecting food security and public health through biosecurity, surveillance, research, and potentially vaccination.

Surveillance should integrate real-time genomics with ecological monitoring to build risk models that forecast high-activity periods and locations, enabling proactive outreach to backyard flocks.

Transmission is now dominated by wild migratory birds rather than domestic poultry-to-poultry spread, creating spatial and temporal unpredictability and diminishing the effectiveness of traditional biosecurity.

Backyard flocks (fewer than 1,000 birds) tend to be infected about nine days earlier than commercial operations, suggesting they can serve as early warning signals.

The earlier onset in small backyard flocks is attributed to lower biosecurity and more outdoor exposure, reinforcing their role as sentinel populations for surveillance.

The study underscores interdisciplinary collaboration across virology, ecology, genomics, and policy analysis to address evolving infectious disease threats and inform global public health strategies.

Despite foreign animal disease classifications, H5N1 is circulating persistently in wild birds in North America, signaling a need to update policies.

Regulatory assumptions that H5N1 is strictly a foreign animal disease with limited endemic wild bird circulation are outdated and surveillance and containment policies should be reconsidered.

Recommended actions include strengthening layered biosecurity, preventing wild-domestic bird interactions, considering vaccination where appropriate, keeping wild and domestic birds separated, and maintaining ongoing wild-bird surveillance.

Using genomic sequencing and migratory flyway analysis, the researchers map how H5N1 moved through North America, drawing on data from Canadian and U.S. agencies.