This is Avian Flu Watch: Global H5N1 Tracker.

We begin today’s episode diving into the latest data on the worldwide spread of highly pathogenic avian influenza H5N1. As of late October 2025, H5N1 outbreaks have affected every continent except Australia, with both animal and human cases creating persistent biosecurity challenges. According to WHO and national health agencies, between January and August 2025 there have been 26 human cases globally, with new fatalities reported in Cambodia, India, Mexico, and the United States.

The current hotspots illustrate a relentless trajectory. In North America, H5N1 has shifted from poultry to dairy cattle, especially in the U.S. West Coast. Mathematical modeling published in Nature predicts that outbreaks in American dairy herds may continue, with Arizona and Wisconsin identified as their next likely epicenters. Over 995 U.S. dairy herds and at least 70 people have been infected, leading to severe outcomes and the first confirmed U.S. human death earlier this year. Canada’s British Columbia region also tracked ongoing poultry and rare human cases.

In South America, data from a multi-country study show the virus spreading primarily through migratory birds along the Pacific flyway. Uruguay and Argentina have seen mass wildlife mortality: more than 24,000 South American sea lions, 400 seals, and hundreds of thousands of wild birds have died since early 2023. Brazil, the world’s top poultry exporter, continues heavy surveillance around Espirito Santo and Rio de Janeiro, now serving as a secondary viral source for neighbors.

Europe’s trend lines are steep. Western and southwestern European states—including the UK, Germany, and Hungary—recorded frequent poultry outbreaks and notable spillover into mammals such as sheep and marine wildlife. Both Germany and Hungary reported thousands of dead cranes. Recent surveillance in the UK found H5N1 in farm sheep, raising concern for interspecies transmission.

Asia’s battle centers on lineage diversity: Cambodia and Vietnam have reported clusters involving older clades with repeated poultry-to-human spillover but no sustained human-to-human transmission. China remains pivotal, with over 275 wild bird cases in Qinghai—critical nodes along migratory flyways are repeatedly infected, risking onward spread to southeast Asia.

If visualizing global trend lines, we’d see pronounced peaks in North and South America early in 2025, with smaller but persistent spikes in Europe and Southeast Asia. Comparative statistics underline a large jump in mammalian cases—especially in cattle and marine mammals—representing an emerging threat for cross-species transmission and potential zoonosis. Notably, H5N1’s genetic drift has produced variants with heightened host range and adaptability, including reassortment between longstanding and newer clades.

International containment efforts have yielded mixed results. Brazil’s animal health emergency and enhanced surveillance have helped delay major poultry sector disruptions. In contrast, U.S. management of dairy herd outbreaks has faced criticism: current interventions, according to CDC data, averted 175 outbreaks but failed to contain further spread. In Europe, coordinated culling and movement controls have slowed but not stopped viral incursions.

Travel advisories remain in effect in multiple regions. The WHO and CDC advise travelers in Southeast Asia and South America to avoid contact with wild birds and domestic poultry. Agriculture workers and veterinarians are urged to wear protective equipment and follow stringent biosecurity protocols.

Thanks for tuning in to Avian Flu Watch: Global H5N1 Tracker. For real-time updates, trends, and next week’s analysis, be sure to join us again. This has been a Quiet Please production. For more, visit QuietPlease dot AI.

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