Welcome to Avian Flu Watch: Global H5N1 Tracker.

Today we bring data-driven insights into the evolving landscape of highly pathogenic H5N1 avian influenza. Since 2020, H5N1 outbreaks have surged worldwide, touching every continent except Australia, with notable escalations in 2025. Worldwide surveillance by the World Health Organization indicates there have been 990 confirmed human cases since 2003, with 475 deaths—a 48% fatality rate. Between January and August 2025 alone, 26 infections were identified and the CDC reports over 70 cases across North America, including recent fatalities in Louisiana and Mexico. In the Americas, the Pan American Health Organization notes 5,063 reported outbreaks since 2022.

Geographically, current hotspots concentrate in South America, Europe, and Southeast Asia. In South America, outbreaks have devastated ecological reserves; Uruguay, Argentina, Chile, and Peru report at least 600,000 wild birds and 50,000 mammals lost since 2022, including record mortality rates among sea lions and Southern elephant seals. In Europe, Germany has seen mass culls—over 500,000 birds removed following 103 separate outbreaks in October, and Hungary lost 10,000 wild cranes. The United Kingdom flagged both human and livestock infections, with H5N1 detected in both poultry workers and farm sheep.

In Asia, China continues to grapple with clustered avian and sporadic human cases, with authorities confirming 275 incidents among wild birds in two Qinghai counties this year. Cambodia witnessed a tragic sequence in early 2025: three human deaths over three months, mostly in children, all linked to close contact with infected poultry. Vietnam and the Philippines also reported fatal human cases, demonstrating the virus’s persistence.

Visualization of the global trend lines shows steady highlights in monthly H5N1 reporting since 2022. Peaks typically align with migratory seasons. Our World in Data graphs reveal pronounced spikes in South America during late 2023, a secondary rise in Europe through early 2025, and a slow but persistent increase in North American cattle and poultry herds.

Comparative analysis shows cross-border transmission strongly correlates with migratory bird flyways: viruses frequently jump species and frontiers along these ecological highways. Notably, genetic studies in China link local virus strains to migratory birds along the East Asian-Australasian and Eastern China Flyways, supporting hypotheses of transcontinental movement. In the United States, recent modeling in Nature underscores the role of interstate livestock shipments; West Coast states, particularly California and Texas, have reported the highest dairy cattle outbreaks, and Arizona and Wisconsin appear at greatest imminent risk.

Successes include rapid containment operations in Argentina, where poultry exports were halted immediately after first industrial outbreaks, and targeted surveillance in US states helped curtail further livestock transmission. Failures exist in late detection among wild marine mammals and in delayed implementation of cattle export testing in the US—measures which, if executed sooner, could have stemmed dozens of outbreaks.

Emerging variants of concern center on clade 2.3.4.4b, now dominant globally and linked to more severe mammalian and human infections. Genetic reassortments in Southeast Asia have combined older and newer viral segments, raising alarms about further adaptation.

International travel advisories urge ongoing vigilance. The CDC and FAO recommend avoiding contact with live birds and unpasteurized animal products, especially near ongoing outbreaks. Travelers are urged to consult local advisories and postpone non-essential visits to high-risk rural sites.

Thank you for tuning in to Avian Flu Watch: Global H5N1 Tracker. Please join us next week for more data and developments. This has been a Quiet Please...