Authorities say bird flu poses a low risk to people right now, but in animals — both wild and domestic — it’s causing global devastation. If left uncontrolled, it could also mutate into something far worse for humans.
Despite the bird flu-related death of a man in the US, the risk of another human pandemic remains low — currently — according to public health agencies and experts.
The man who died in November 2025 was the first human case in the US since January. He did not appear to have passed the disease to anyone else, which experts say keeps the risk of a new and major human disease outbreak minimal. The same is true for other human bird flu cases in 2025.
But for animals, the disease has been devastating.
“It’s not, any longer, only an impact on the poultry sector or wild birds,” Gregorio Torres, head of science at the World Organization for Animal Health (WOAH), told DW.
Data obtained by DW shows almost nine million poultry birds have been culled worldwide since October, mainly in the US, Canada and in Germany, as both North America and Europe grapple with outbreaks on farms and in the wild.
And the effect has spread beyond birds. The current wave, largely of the H5N1 subtype, has seen cattle, pigs, cats and dogs, and wild mammals infected as well.
Bird flu: Disease and death
Highly pathogenic avian influenza — HPAI — refers to those bird flu viruses that cause severe infection in poultry.
Though the designation of these viruses is based on how they affect chickens, ducks, turkeys and other poultry, the effect of infection is usually the same as for wild birds — disease and then death.
WOAH, which is an intergovernmental organization responsible for coordinating and monitoring animal health across the globe, views the virus — specifically the 2.3.4.4b clade of H5N1 bird flu that is driving most infections in animal species — as a major threat to biodiversity.
Management of disease outbreaks is an intensive task. Collaboration between animal monitors, such as WOAH, veterinary and wildlife scientists and human public health agencies, is considered critical for controlling the spread.
Low risk to humans for now, high impact on animals
HPAI has been detected on every continent in 2025, both on land and at sea.
The scale was highlighted on November 25 when Australian authorities confirmed bird flu had reached its remote, sub-Antarctic, Indian Ocean territory of Heard Island — around 4,300 kilometers (2,600 miles) southwest of the mainland — where it has infected elephant seals.
Bird flu has previously caused widespread death in similar populations along South America’s coastlines. Researchers have also detected infections in dolphins.
But bird flu continues to trouble the agricultural sector most of all.
In fall 2025, German poultry farmers were confronted with an unwelcome early start to the bird flu season, with the disease being spread by migrating cranes from Sweden for the first time. This has led to more than a million poultry being culled in Germany.
Migrating birds are the chief reason bird flu spreads across continents.
As they flee the northern hemisphere when winter approaches, these birds make stopovers near wetlands to rest and recover. These stopovers can bring them into contact with local bird populations.
Mutations make bird flu spread easier
If infected with HPAI, there is a high chance migratory birds will transmit the pathogen to other wild or farm birds, setting off chain reactions of transmission. Recent research shows mutations in the 2.3.4.4b clade of H5N1 have made infection with all wild birds easier.
That means an airdrop of the disease among local duck, swan or geese populations can effectively bring it to a region, where it may then continue to spread even without the help of migratory birds.
Part of the solution lies in “strong biosecurity” measures, experts told DW, meaning governments should have strict protocols in place to ensure agricultural spaces minimize bird flu risks at their local level.
Strong biosecurity is essential for containing outbreaks, preventing transmission and reducing the risk of future episodes, said Justin Bahl, an epidemiologist and evolutionary biologist at the University of Georgia, US.
“As long as we have biosecurity and we are being vigilant, then I think we’re in a good place right now,” Bahl told DW. “Lax biosecurity is probably the bigger risk.”
Controlling the spread of the virus among animals reduces the risk of a worse-case scenario — a mutation that makes transmission to, and potentially among humans, easier.
It’s a view echoed by Amira Roess, a global health epidemiologist at George Mason University, US. Roess told DW that active surveillance and disease testing helps to prevent bird flu spread among bird flocks, but that it also reduces the risk of mutations that could make transmission to humans easier.
Source : https://www.dw.com/en/virus-has-killed-almost-9-million-birds-and-counting/a-74972319
