Welcome to Avian Flu Watch: Global H5N1 Tracker, your data-focused update on the worldwide spread of highly pathogenic avian influenza, H5N1, as of late October 2025.

Let’s start with a geographic breakdown. According to the Centre for Health Protection and the Pan American Health Organization, H5N1 outbreaks and documented human and animal infections are active on every continent except Antarctica. In the Americas, there have been over 5,000 outbreaks since 2022, with hot spots in the United States, Mexico, and Argentina. Notably, in the US, recent CDC and USDA reports show over 173 million infected poultry and more than 1,000 dairy cow herds affected, plus 70 human cases this year. In South America, outbreaks in Argentina and Brazil have shown distinct transmission routes influenced by migratory birds, with Uruguay serving as a critical hub for both avian and marine mammal-derived lineages.

Europe remains heavily impacted. The European Centre for Disease Prevention and Control notes that between June and September 2025, western and southwestern Europe saw predominant H5N1 activity. Recent government reports indicate confirmed outbreaks in commercial poultry across England, Wales, Northern Ireland, Germany, Italy, Spain, Latvia, and the Czech Republic. England alone has confirmed 8 cases in the current outbreak season.

In Asia, ongoing surveillance in China’s major flyway provinces—Jiangsu, Shandong, Henan, and Hebei—has detected genetically diverse H5N1 strains related to those in South Korea and Japan, underscoring the virus’s rapid evolution and the role of wild bird migrations in spreading new variants.

Visualizing these trends, global case counts can be imagined as steep upward curves in both poultry and spillover infections: a persistent baseline in endemic regions like Egypt and Indonesia, while North and South America, and parts of Europe, spike with seasonal epizootics tied to migratory patterns and agricultural practices. The data reveal a troubling increase in cross-species transmission, such as the unprecedented jump to cattle in the US and marine mammals in South America, illustrated by adding new branches on the H5N1 transmission map.

Comparing statistics year-on-year, the 2024–2025 season saw a marked uptick in North American livestock involvement. Earlier years focused predominantly on wild birds and poultry, but now the trajectory includes mammals—a significant shift. This year, human case numbers remain relatively low compared to animal outbreaks, with 26 global infections between January and August, but the potential for zoonotic spillover remains high.

Cross-border transmission continues to challenge containment. Migratory birds facilitate long-distance jumps between continents, while international trade and livestock movement present additional risks—highlighted by mathematical modeling from Nature, which predicts continued outbreaks across American farm states and identifies Arizona and Wisconsin as likely next hotspots if surveillance isn’t strengthened.

Containment efforts show mixed results. The UK and EU imposed strict poultry movement controls, curbing local spread but unable to halt new introductions from wild birds. In the US, biosecurity in dairy and poultry farms has slowed but not stopped the epidemic. In South America, coordinated monitoring has shown some success containing outbreaks in Uruguay, but emerging variants—especially in hosts like marine mammals—challenge regional One Health frameworks.

Emerging variants of concern include the 2.3.4.4b clade, with bovine-derived strains capable of infecting multiple mammal species. Evolutionary divergence in China’s isolates points to ongoing adaptation and possible pandemic threats if human-to-human transmission efficiency rises.

Given current transmission dynamics, health organizations recommend those traveling to outbreak zones avoid contact...