Bird Flu Outbreaks Spread Worldwide, Threatening Millions of Birds

Across Europe, North America, and beyond, bird flu is leaving a devastating mark on animal populations. While human infections remain rare, the virus has caused widespread death in domestic poultry, wild birds, and even some mammal species.

Authorities report that almost nine million poultry have been culled worldwide since October 2025, particularly in the United States, Canada, and Germany. The losses extend far beyond farmed birds. Migratory waterfowl, wild mammals, and even domestic pets have been affected, underscoring the virus’s wide reach.

Understanding the Virus

The current outbreaks are driven largely by the highly pathogenic H5N1 virus, specifically the 2.3.4.4b clade. Highly pathogenic avian influenza (HPAI) can cause severe disease and death in chickens, ducks, turkeys, and other poultry, and the effects are similarly lethal in many wild bird species.

Gregorio Torres, head of science at the World Organization for Animal Health (WOAH), called the virus a significant threat to biodiversity. Controlling outbreaks requires careful coordination among veterinary experts, wildlife specialists, and public health authorities.

Global Spread and Impact

HPAI has been detected on every continent in 2025, including in remote locations such as Heard Island in the sub-Antarctic Indian Ocean, where infections have been reported in elephant seals. In Germany, migrating cranes have carried the virus into domestic flocks, prompting the culling of more than a million birds.

Migratory birds play a key role in transmission. As they travel south for the winter, they make stopovers that can introduce the virus to local wild and farmed birds. Recent studies show that mutations in the virus have made it easier for H5N1 to infect a broader range of avian species, increasing the potential for rapid spread.

Mitigation and Biosecurity

Experts emphasize that strong biosecurity measures on farms and strict surveillance of wild populations are critical to limiting transmission. Justin Bahl, an epidemiologist at the University of Georgia, noted that vigilant biosecurity is the most important tool in preventing further spread.

Active monitoring not only helps protect birds but also reduces the risk of viral mutations that could increase the potential for human infection. While 2025 has seen a small number of human cases, including a fatality in the U.S., public health officials maintain that the risk of a widespread human outbreak remains low.

A Global Challenge

Cooperation across borders is essential. Wild birds do not recognize national boundaries, and viruses can spread quickly if nations fail to share surveillance data. Torres emphasized that transparency and collaboration are critical for the health of both humans and animals.

For now, the focus remains on protecting poultry and wild bird populations while monitoring potential changes in the virus. Scientists continue to study the H5N1 clade closely, aiming to prevent future outbreaks and safeguard global biodiversity.