Welcome to Avian Flu Watch: Global H5N1 Tracker, your data-focused briefing on the rapidly evolving landscape of bird flu around the world as of October 2025.

Let’s start with the headline stats. According to the Pan American Health Organization, since 2022, more than 5,000 outbreaks of H5N1 have struck 19 countries and territories in the Americas alone, with 76 reported human infections and two deaths in this region. Globally, the World Health Organization reports a cumulative total of 990 confirmed human H5N1 cases and 475 deaths in 25 countries since 2003—a 48% case fatality rate. Over the past year, outbreaks have intensified, not just in poultry, but alarmingly in wild birds and mammals, including seals and even cattle.

Geographically, cases are highest in:
- The United States, where outbreaks in poultry remain ongoing, and dairy cattle became an unexpected host in 2024. CDC figures cite 173 million infected poultry, over 1,000 affected dairy herds, and at least 70 human cases as of late May 2025. CDC and Nature report most US transmission remains on the West Coast, but clusters have now emerged in Texas, Louisiana, Ohio, and Wyoming. Interstate movements of cattle have facilitated spread, especially into risk-prone states like Arizona and Wisconsin.
- In South America, Chile, Uruguay, and Argentina have suffered mass die-offs among wild birds and marine mammals, with at least 600,000 wild birds and 50,000 mammals killed since 2022. Argentina’s elephant seal populations were hit especially hard, with mortality rates up to 96%.
- Southeast Asia continues to report sporadic human infections—five in Cambodia and one fatal case in Vietnam in early 2025. Notably, Cambodian cases involve direct poultry exposure, while genetic sequencing reveals both the older 2.3.2.1c clade and reassortant viruses emerging in the Greater Mekong region.
- Europe: Germany reported over 2,000 crane deaths and at least 15 poultry farm outbreaks. The UK documented human infection and spillover to sheep, highlighting growing mammalian vulnerability.

Visualization of reported trend lines would show a steep climb in mid-2024, particularly in the Americas and Europe, followed by recurrent regional peaks driven by migratory bird seasons aligning with outbreaks along major flyways. The Andes-to-Patagonia wild mammal mortality spike and US West-to-Midwest cluster jumps are especially prominent.

Cross-border transmission remains driven by two factors: migratory wild birds and livestock trade. The Friedrich Loeffler Institute and China CDC note that major flyways—such as the East Asian-Australasian and Atlantic Americas routes—are key highways for virus spread. The US cattle trade itself, with nearly 30,000 annual interstate exports, highlights how livestock movements can amplify and disseminate the pathogen even under enhanced testing regimes. Genetic analyses show independent viral evolution in Asia and the Americas, with both regions now harboring highly pathogenic clade 2.3.4.4b variants.

Containment efforts have varied in success. A temporary export ban on avian products in Argentina helped prevent wider market-driven spread. In the US, new mandatory testing of cattle for interstate transport, initiated in April 2024, has slowed cross-state infection but not stopped it, signaling more urgent farm biosecurity is needed. Failures include long delays in detection among dairy cattle and inconsistent reporting across countries, leaving gaps in surveillance.

Emerging variants of concern include reassortant viruses in Southeast Asia, which mix genes from poultry and wild birds, and the expansion of bovine-adapted strains in North America with demonstrated capacity to jump to cats, raccoons, and rodents.

International authorities including the CDC, WHO, and ECDC urge travelers and agricultural workers to avoid live animal markets, contact with sick or dead...