What you need to know:
- A second type of bird flu H5N1 detected in US cattle
- Some experts believe the risk for humans is low
- Infections have been detected outside the US, in the UK
- European authorities are monitoring the North American outbreak
With the detection of genotype D1.1 avian influenza in dairy cows in January 2025, US authorities said it was proof that bird flu had spread from wild birds into cattle twice in an outbreak that started in late 2023.
The genotype refers to the genetic makeup of a virus, within a group of virus types. In this case, it is highly pathogenic avian influenza (HPAI) A H5N1.
In March 2024, authorities in the US confirmed the outbreak originated from genotype B3.13. That type has infected more than 950 cattle herds in 16 US states and spread to Canada.
D1.1 was detected in milk collected as part of a surveillance program launched in December 2024.
Is bird flu spreading internationally?
Yes, it appears that bird flu from the current US outbreak may spread beyond North America.
In January 2025, UK authorities confirmed a second human case of H5N1 avian influenza. The first was detected in 2022, the UK Health Security Agency (UKHSA) said.
Susan Hopkins, chief medical adviser at the UKHSA, said: “The risk of avian flu to the public remains very low, despite this confirmed case.”
But many governments have been buying up vaccine stocks and ramping up precautionary measures in response to the circulating virus.
The outbreak has mainly affected the US, with infections among cattle, people and pets.
Though no cases of direct, human-to-human transmission were recorded up to January 2025, there are concerns the H5N1 variant could be one mutation away from becoming a major public health concern.
A study published in the journal Science in December 2024 found that a single genetic change to the circulating H5N1 had enabled it to jump more easily from other mammals to humans.
“We’re particularly worried about pigs because we know from many other outbreaks that pigs are a mixing vessel for influenza viruses,” Meghan Davis, an environmental health researcher at Johns Hopkins Bloomberg School of Public Health, told DW’s Science Unscripted podcast.
Is a new pandemic brewing?
Prior to the outbreak of SARS-CoV-2 — the virus that causes COVID-19 — health scientists warned that there was a risk of an emerging pandemic.
Ultimately it was a novel coronavirus and not an influenza strain that triggered the pandemic. But the chance of a global influenza-driven event was — and is — cause for concern.
“With H5N1, there’s a big unknown,” Peter Jay Hotez, dean of the National School of Tropical Medicine at the Baylor College of Medicine in the US state of Texas told Science Unscripted.
“We know there’s a likelihood that there could be a significant bird flu pandemic, maybe resembling the 1918 flu pandemic,” Hotez said, “but we can’t say when that will be.”
Other nations are increasing surveillance and precautionary measures. The UK government is known to have ordered at least five million doses of an H5 influenza vaccine. In November 2024, one case of H5N1 was confirmed at a poultry farm in Cornwall, in the south-west of England.
“I agree with what the UK did because it’s not like you can press a button and suddenly have millions of doses of [H5 vaccine] appear,” Hotez said. “Making flu vaccine by the traditional way is a slow process.”
Hotez describes the rate of pandemic threats as having a “regular cadence,” pointing to SARS in 2002 and MERS in 2012, which were dangerous but did not balloon to a global scale.
A pandemic was declared due to H1N1 influenza in 2009, though its impact didn’t match that of COVID-19.
“We have to get ready for H5N1. We’ve also got this rise in Ebola and other filovirus [severe hemorrhagic] infections that we’re seeing — we have to be ready for that,” Hotez said. “And we’re starting to see [a rise in] mosquito transmitted virus infections like and chikungunya and then infections both in Southern Europe and the southern United States.”
‘They’re contrarians, they’re activists’
Scientists and health experts in the United States have expressed concern about several appointments that President-elect Donald Trump has made for his administration.
Among Trump’s picks were and Dave Weldon for the top job of the Centers for Disease Control and Prevention.
Kennedy and Weldon are known for their opposition to vaccination.
Although Trump was president at the outset of the coronavirus pandemic and led massive investment in vaccine supply security through programs such as Operation Warp Speed, Hotez said the absence of people with established experience in health issues in Trump’s new administration is concerning.
“[In Trump’s first administration] they were pretty mainstream public health physicians and public health scientists, but this new round is something that’s quite different — they’re contrarians, they’re activists, they’ve openly campaigned against vaccines and interventions,” Hotez said.
Health experts in other nations are closely watching how H5N1 is handled in North America.
“The current incidence of infection in the US demands we closely study samples of viruses from humans and other animals,” said Martin Schwemmle, a virologist at Freiburg University Medical Center.
The European Centre for Disease Prevention and Control said in a November 2024 report that it was continuing to monitor the US and Canadian situations “together with partner organizations in Europe and will continue to update its assessment of the risk for humans … as new information becomes available.”
It also recommended increased surveillance and monitoring of people exposed to avian influenza, and that doctors and nurses ask patients whether they have had any contact with animals.
Edited by: Zulfikar Abbany
Sources:
USDA Reported H5N1 Bird Flu Detections in Poultry, US Centers for Disease Control and Prevention (CDC) https://www.cdc.gov/bird-flu/situation-summary/data-map-commercial.html
H5 Bird Flu: Current Situation, US Centers for Disease Control and Prevention (CDC) https://www.cdc.gov/bird-flu/situation-summary/index.html
Global Avian Influenza Viruses with Zoonotic Potential situation update, United Nations Food and Agriculture Organization https://www.fao.org/animal-health/situation-updates/global-aiv-with-zoonotic-potential/en
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