Hundreds of thousands of chickens have been culled because of the menace of hen flu
Emily Elconin/Bloomberg through Getty Photographs
The US skilled its first identified hen flu deaths this 12 months, igniting issues that the virus might set off a pandemic in folks. However, it nonetheless reined within the outbreak sufficient to warrant ending its emergency response – however public well being consultants warn the battle is way from over.
“It’s nonetheless a pandemic in [non-human] animals,” says Meghan Davis at Johns Hopkins College in Maryland. “And the virus is not any much less lethal now than it was earlier than.”
The pathogen behind the overwhelming majority of instances, a subtype of avian influenza referred to as H5N1, first emerged in poultry in China in 1996. It then resurfaced in 2021, devastating international hen populations and spreading to a number of mammals, together with foxes, seals and cats.
H5N1 is poorly tailored to infecting people and isn’t identified to transmit between folks. However it nonetheless poses a big menace, having killed virtually half of the practically 1000 folks identified to have contracted it worldwide since 2003. These fatalities in all probability symbolize extreme instances, with most milder incidences going unrecorded. However, the danger to folks exists, and could be even larger if the virus had been to evolve the flexibility to unfold from individual to individual – a state of affairs that would spark a pandemic, says Davis.
That’s the reason public well being consultants had been alarmed when H5N1 started circulating amongst dairy cows within the US in March 2024, the primary identified occasion of it infecting dairy cattle. Not solely did this put the virus in shut proximity to folks, notably farm staff, however it afforded it considered one of its greatest alternatives but to adapt to unfold between people. Every time the pathogen infects an individual or one other mammal, it has an opportunity to amass mutations obligatory for human-to-human transmission, says Davis.
H5N1 has since been detected in additional than 1080 herds throughout 19 US states, whereas additionally hounding poultry farms. Between February 2022 and mid-December, it sickened at the very least 1950 flocks nationwide, forcing farms to cull practically 200 million birds.
The farm outbreaks subsequently fuelled a spike in human instances. Of the 71 folks who’ve ever examined constructive for hen flu within the US as of December 2025 all however six contracted it from contaminated dairy cows or poultry. As to these six instances, three contracted it from one other animal supply, whereas the origin of the remaining three incidences is a thriller, though there isn’t purpose to imagine they picked it up from one other individual.
Many of the human instances skilled gentle signs, reminiscent of eye redness, and made a full restoration. Nonetheless, an individual in Louisiana with underlying well being situations died from the H5N1 virus in January – the primary identified demise associated to hen flu within the US.
Since then, the nation has largely wrangled the outbreak beneath management. The final time somebody examined constructive for H5N1 was in February, says Emily Hilliard, the press secretary on the US Division of Well being and Human Providers. Nonetheless, a person in Washington state examined constructive and died attributable to a special, although associated, hen flu pressure, referred to as H5N5, in November after being uncovered to contaminated poultry.
“What’s considerably reassuring is {that a} traceback investigation from the deadly H5N5 case has not uncovered every other human instances, nevertheless, the pandemic potential for H5 viruses stays, notably given the flexibility of those viruses to have an effect on mammals, together with people, and to unfold from mammal-to-mammal,” says Davis. The US Facilities for Illness Management and Prevention (CDC) says it’s watching the state of affairs fastidiously and the danger to the general public is low.
Infections of H5N1 in dairy cattle have additionally plummeted, with the US Division of Agriculture (USDA) reporting solely two herds have examined constructive between November and mid-December.
These declines finally led the CDC to finish its emergency hen flu response in early July, says Hilliard. The response, initiated in April 2024, allowed the company to deploy extra employees and sources in direction of surveillance and mitigation effort, she says.
There are a couple of attainable explanations as to why instances declined. For one, the USDA launched its Nationwide Milk Testing Technique in December 2024, mandating dairy farms to supply uncooked milk samples for H5N1 testing. “Testing is completely central to any management technique,” says Davis. “Should you don’t know the place [H5N1] is, then mandating extra protections or imposing quarantine of farms simply can’t occur.”
In February, the USDA additionally introduced a $1 billion technique for curbing H5N1 on poultry farms, together with elevated funding for vaccine analysis and biosecurity measures. Considered one of its focuses was to shore up defences towards wildlife. “The overwhelming majority of [bird flu] introductions into home poultry and livestock have been traced to contact with contaminated wild birds,” says a USDA spokesperson. By mitigating H5N1 on farms, these efforts in all probability additionally diminished instances in folks, given most infections occurred in dairy staff, says Davis.
Nonetheless, it is also attributable to seasonal fluctuations. “We’ve got seen lulls in the summertime adopted by explosive instances within the fall and winter,” says Davis. “So, what you have a tendency to search out is that in migration season, which we’re in in the meanwhile, you begin seeing extra instances.”
Migratory birds introduce the virus to farms as they journey, which might be why detections of H5N1 in yard and industrial poultry flocks elevated by greater than 130 per cent between September and October. “What we haven’t had are lots of human instances,” says Davis. However whether or not this is because of elevated safety measures or diminished surveillance in staff isn’t clear, she says.
“I’m inspired that we’ve seen a declining variety of instances,” says Davis. “However I feel there may be nonetheless extra that we have to do.”
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