Bird flu cases in mammals double – what does this mean for risk of human spread?

Outbreaks of in mammals more than doubled across the world last year, raising the risk that the virus could potentially spread between humans, an international agency warned this week.

Avian influenza has spread across the world like never before in the last few years, leading to the mass culling of poultry, sending egg prices soaring, and causing the deaths of several people in contact with infected animals. © Moisés ÁVILA / AFP

Avian influenza has spread across the world like never before in the last few years, leading to the mass culling of poultry, sending egg prices soaring, and of several people in contact with infected animals.

While the overall risk of human infection remains low, bird flu outbreaks among mammals such as cattle, dogs, increase the possibility that the virus could eventually adapt to transmit between humans, the World Organisation for Animal Health (WOAH) said in a new .

The number of mammal outbreaks soared to 1,022 across 55 countries last year, compared to 459 in 2023, according to the Paris-based agency, which monitors animal diseases worldwide.

"It is concerning because it is a change in the pattern of the epidemiology of the virus," WOAH's director general Emmanuelle Soubeyran said.

Health experts have been sounding the alarm about the posed by bird flu, which has shown signs of mutating as it spreads, particularly in the US.

The new report comes as the budgets of US health and science agencies have been slashed by the Trump administration.

This included earlier this year of the staff of an epidemiology program known as the "disease detectives."

While the overall risk of human infection remains low, bird flu outbreaks among mammals such as cattle, dogs, and cats increase the possibility that the virus could eventually adapt to transmit between humans, the World Organisation for Animal Health (WOAH) said in a new report. © Unsplash/Anastasiia Chepinska Reports calls bird flu "a global emergency" effecting many sectors The US Department of Agriculture issued a federal order in April 2024 requiring the testing of the nation's milk supply amid increasing concerns over HPAI (a strain of the H5N1 avian flu), which has been raising alarm since it was first detected in a Texas cow. © MICHAEL M. SANTIAGO / GETTY IMAGES NORTH AMERICA / GETTY IMAGES VIA AFP

Bird flu "is more than an animal health crisis – it is a global emergency destabilizing agriculture, food security, trade, and ecosystems," the report warned.

More than 630 million birds have either died from avian influenza or been culled due to it over the last two decades, according to the agency's first annual State of the World's Animal Health report.

Wild birds have also suffered mass die-offs, although the exact number is difficult to estimate.

The report highlighted the role that can play in stemming outbreaks among birds – which in turn decreases the risk to mammals and humans.

It cited the example of France, which started against bird flu in 2023.

Modeling from the Toulouse Veterinary School estimated there would be 700 outbreaks in France that year. In the end, there were just 10, the report said.

Soubeyran said this was a "win-win" because it reduced exposure to humans – and meant there were more poultry products available for export.

However, she emphasized that vaccines were not a "magic wand" and did not suit every situation.

The latest update on the continued spread of high pathogenicity avian influenza across the world:
- 59 outbreaks reported in poultry and 44 in non-poultry birds and mammals across the Americas, Asia and Europe.
- Approximately 3.76 million poultry deaths or cullings, mostly in… pic.twitter.com/GA3RRdKbkM

— World Organisation for Animal Health (@WOAH) May 23, 2025

Biosecurity, surveillance, increased transparency, and global collaboration are also important tools to fight off the threat of bird flu, Soubeyran added, calling for more investment in these areas.