This is Avian Flu Watch: Global H5N1 Tracker—a data-focused update on the worldwide spread of highly pathogenic avian influenza, H5N1.

As of October 2025, H5N1 continues to affect both animal and human populations across continents. According to the World Health Organization, there have been 973 confirmed human cases since 2003, with 470 deaths, representing a case fatality rate of about 48 percent. In the last year alone, new clusters of human infections have emerged in Cambodia, India, Mexico, the United States, and the United Kingdom, with cases frequently linked to direct contact with infected poultry or, more recently, contaminated mammalian hosts.

Let’s break down the current hotspots. Southeast Asia remains a focal point, with Cambodia reporting three fatal human cases since January 2025. India and Mexico each reported fatal human cases this spring, underlining the virus’s increasing geographic reach and ability to cross traditional species barriers. In the United States, the CDC has tallied multiple human cases in 2025, notably in Louisiana, Ohio, and Wyoming, with the country continuing to experience mass poultry culls, including the loss of 20 million chickens in late 2024.

Visualizing recent trend lines, data from PAHO reveals a sharp increase in animal and human infections in the Americas from late 2024 through 2025. Charts show a continued upward trend, especially in the US West Coast states, where mathematical models cite persistent outbreaks among dairy herds, and the risk of spillover to other states like Arizona and Wisconsin remains significant. Across Asia, figures from WHO highlight recurring surges in Cambodia and Viet Nam, while Europe and the UK see a steadier, moderate increase in outbreaks.

Comparative statistics show that, in 2025, outbreaks in mammals—including dairy cattle, seals, and even polar bears—have reached unprecedented levels. These cross-species jumps are concerning; for example, the US first detected H5N1 in dairy cattle in early 2024, with ongoing transmission facilitated by cattle movement between states, despite federal testing and movement restrictions. Genetic sequencing in the Middle East and Greater Mekong region shows evidence of viral reassortment, as older and newer clades recombine, complicating containment.

Patterns of cross-border transmission are notable along migratory bird flyways and through livestock trade. Outbreaks frequently occur near borders where animal trade is common, such as between Egypt and Israel, Turkey and neighboring countries, or across the US-Canada and US-Mexico borders. Wild bird migrations remain a critical factor in transcontinental spread, from the Arctic all the way to South America, including recent incursions into Antarctica’s wildlife.

Notable containment efforts include swift poultry culls and export bans in the UK, Philippines, and Brazil, and increased farm biosecurity measures in the US, yet gaps in surveillance and uneven implementation have hampered broader success. Failures are most evident where delayed detection allowed the virus to establish in new species or regions, as seen with the late 2024 spread into US dairy cattle.

New variants of concern have been reported, including reassorted strains that blend genes from both the 2.3.4.4b and older 2.3.2.1c clades in Southeast Asia, raising alarms over increased zoonotic potential and complicating vaccine development. Surveillance agencies warn that these changes may enable more efficient mammal-to-mammal or even limited human-to-human transmission.

As for travel, health authorities urge caution when visiting outbreak regions, especially for those involved with poultry or livestock farming, encouraging strict adherence to biosecurity and hygiene measures. Several countries, including Taiwan and the Philippines, have issued or extended travel advisories for Southeast Asia and select areas in the...