Avian Flu Watch: Global H5N1 Tracker

Welcome to Avian Flu Watch: Global H5N1 Tracker, your scientific data briefing on the current spread of H5N1 avian influenza. Around the world, H5N1 remains a serious zoonotic threat, with outbreaks surging in both wild birds and mammals, and increasingly crossing into new geographic regions and species.

First, a global overview. The Americas persist as a major hotspot. The Pan American Health Organization reports that, since 2022, 19 nations in the region have recorded over 5,000 H5N1 outbreaks in poultry and livestock. Human cases in the Americas reached 76 since 2022, with two confirmed fatalities. Worldwide, historic data from the World Health Organization totals 990 human cases since 2003, with 475 deaths—a case fatality ratio near 48 percent. In 2025 alone, the CDC identified 26 new human infections between January and August.

Europe has seen pronounced spread, especially in poultry farms and wildlife reserves. This October, Germany culled half a million birds amid 103 new outbreaks. Nearby Hungary lost 10,000 cranes, and the UK confirmed a human infection in a farm worker and unusual mammalian cases, such as sheep displaying avian influenza symptoms.

Asia remains on high alert for both animal and human infections. Cambodia is frequently cited, with several fatal human cases tied to direct poultry contact in early 2025. India, China, and Bangladesh all reported new human cases from June to September. Cambodia alone confirmed 11 cases, with two deaths, during that period, according to the ECDC. Notably, new viral lineages are being mapped in Southeast Asia, suggesting ongoing reassortment—the mixing of genetic material from multiple H5 lineages. This raises alarms about evolution, adaptation, and potential mammalian spillover.

Let’s visualize trend lines. Data aggregated by Our World in Data and the CDC show infection spikes among wild birds in early 2024, followed by plateauing midyear. However, the current season has brought new surges among livestock—especially cattle—and a rise in interspecies transmission events. Europe’s recent 19 documented human H5N1 cases from June to September underscore the persistent threat. Visual graphs of case numbers reveal a sawtooth pattern, with outbreaks peaking during migration seasons and major farming cycles.

Cross-border transmission patterns center on migratory birds and international livestock trade. US outbreak models indicate most cattle infections concentrated in West Coast states like California, with Arizona and Wisconsin emerging as probable next epicenters. Interstate cattle movements remain a key epidemiological driver—border testing is federally required for exported cattle, but mathematical models published in mid-2025 suggest these interventions alone are insufficient to curb the spread. The true extent of infections may be underreported, with silent reservoirs likely in regions such as Florida and the Midwest.

Internationally, containment remains uneven. While early detection and mass culling in Germany and the UK averted wider spillover, inconsistent biosecurity in Southeast Asia and Latin America enabled further outbreaks. A promising sign is the rapid quarantine response in US cattle herds, yet delays and incomplete reporting undercut effectiveness.

The dominant global variant, clade 2.3.4.4b, now infects birds, cows, sheep, and even domestic pets. Evidence from recent studies and CDC reports warns that raw milk and contaminated dairy products could become a new route of transmission to humans, further complicating containment.

Current travel advisories by the CDC and WHO urge caution for those visiting affected regions, particularly around live animal markets and poultry farms. Individuals working in agriculture should follow enhanced surveillance and biosecurity measures.

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