H5N1 Bird Flu Spreads Globally: Alarming Cattle Transmission and Human Cases Signal Emerging Pandemic Risks in 2025

This is Avian Flu Watch: Global H5N1 Tracker. Today, we’re examining the worldwide spread of H5N1 bird flu, focusing on the latest data, regional trends, and emerging risks. The H5N1 virus remains active on every continent except Antarctica. In North America, the United States continues to be a major hotspot. The Centers for Disease Control and Prevention reports nearly 70 human cases since April 2024, with more than 165 million birds affected, and over 970 herds of cattle and dairy cows across 17 states testing positive. Transmission into mammals—especially cattle—has fundamentally changed the surveillance picture and underscores ongoing risks. Pasteurization measures for milk and heightened on-farm biosecurity are in effect, as contaminated equipment and human movement facilitate farm-to-farm spread. Turning to Asia, Cambodia has been hit hard in 2025—with 11 confirmed human cases and six fatalities in the first half of the year, mostly in Siem Reap, Takeo, and surrounding regions, according to the World Health Organization. Children and working-age adults exposed to sick backyard poultry are most frequently infected. Since the re-emergence of human cases in 2023, Cambodia has recorded 27 human cases and 12 deaths. Neighboring countries remain vigilant, increasing surveillance in border provinces. In Europe and the Middle East, Turkey and Lebanon have served as significant transmission corridors, facilitating cross-border viral movement among poultry. Genetic analyses show close relationships between strains in Turkey, Egypt, Israel, and Gaza, pointing to an interconnected transmission web and shared risk factors. The emergence of the D1.1 variant in Nevada dairy cattle in February 2025 signals continued viral evolution and an elevated risk of further cross-species jumps and reassortment. Visualizing the global trend line, case numbers in poultry and cattle have risen sharply since 2024, then plateaued in North America in early 2025 amid enhanced containment. However, Southeast Asia’s trend line continues to climb, driven by sporadic human cases. Spikes occur in regions with both high agriculture density and limited biosecurity. Comparatively, the United States has seen the largest non-avian outbreaks, with Europe mostly containing avian cases and Southeast Asia posting the highest recent human case fatality rates. Notably, the cross-species transmission into mammals—and especially cows—distinguishes this period from previous outbreaks, aligning with reports of genetic changes in newly emergent virus clades. On containment, North America’s rapid mass culling and vaccination efforts have helped slow agricultural spread, yet sporadic spillover into humans persists, especially among farmworkers. Southeast Asia faces greater struggles, especially in rural poultry-rearing communities, where containment and education measures lag behind virus transmission. Emerging variants such as B3.13 and D1.1 exhibit distinct properties related to host rec This content was created in partnership and with the help of Artificial Intelligence AI.