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Why are US health officials growing concerned about bird flu? What mutations are scientists finding in recent human cases? Will there be a bird flu pandemic in 2025?
Bird flu has spread rapidly through US dairy farms and poultry operations, infecting nearly 1,000 dairy herds and causing mostly mild illness in dozens of exposed workers. While bird flu hasn’t been transmitted between humans yet, health officials are concerned that it could be.
Here’s a look at the situation and the studies.
Bird Flu Is on the Rise
Last week a person in Louisiana died from bird flu—the first such death in the US—after genetic analysis revealed mutations help the virus more easily infect humans. The death intensifies efforts to contain an outbreak that’s spread through nearly 1,000 dairy herds and infected dozens of people across the country. This is leaving Americans wondering if there will be a bird flu pandemic in 2025.
H5N1 Background
The deadly bird flu (H5N1) virus, which resurfaced in Europe in 2020, has now spread across every continent except Australia. H5N1 has infected an unprecedented range of species, moving beyond wild birds and poultry to affect various mammals, including seals, dolphins, cats, and dogs.
The outbreak took a dramatic turn in March 2024 when the US detected the first H5N1 cases in dairy cows. By April, the virus had spread through multiple herds across several states, with FDA testing revealing bird flu traces in 20% of US commercial milk samples.
A Look at the Outbreak
The H5N1 bird flu outbreak has expanded dramatically in the US, infecting 917 dairy cow herds across 16 states, as of January 7, 2025. The virus has severely impacted the poultry industry, with the Department of Agriculture documenting infections affecting over 25 billion birds in 50 commercial and 38 backyard flocks.
Human infections have increased steadily since April 2024, with the Centers for Disease Control and Prevention (CDC) confirming 64 cases nationwide. The majority stemmed from human contact with infected dairy cows (39 cases) or poultry (22 cases), while two cases had no clear source. Though most people experienced mild symptoms like eye inflammation and respiratory issues, the virus recently proved lethal in Louisiana.
| Lessons From E. Coli Outbreaks In his book Fast Food Nation, Eric Schlosser discusses how E. coli can spread among cattle. While the situation is different, it gives us some insight into how diseases spread among farm animals. E. coli in beef has likely been present in American cattle herds for decades. But until the rise of industrial-scale, centralized meatpacking driven by the demands of the fast food industry, its spread was fairly limited. The disease gets its start in the vast feedlots of today’s slaughterhouses. These facilities are marked by appalling sanitary conditions, where the cattle are packed into close quarters, given little exercise, and splash around in pools of manure. This creates ideal conditions for bacteria to grow and make the animals sick. This is exacerbated by what the cattle are now increasingly being fed: the rendered remains of dead sheep and other cattle, as well as dead dogs and cats purchased from animal shelters. Natural herbivores, cows’ stomachs are not designed to eat other animals. Forcing them to do so is not only inhumane and cruel, but also facilitates the growth of deadly parasites in their bodies that are then passed on to the humans who eventually consume their meat. Things get even worse after the animals are slaughtered. When workers improperly pull out the stomach and intestines of the cattle by hand, they often spill the contents of the digestive system all over the slaughterhouse floor. With the industry’s relentless focus on speed and scale, much of this finds its way into the meat that’s sold to consumers. Similarly, these workers are rarely instructed in how to clean and disinfect the knives they use to cut cattle carcasses. |
H5N1 Genetic Analysis
Recent genetic analyses of H5N1 virus samples have found mutations that could strengthen the virus’s ability to infect humans.
- In December, samples from the critically ill Louisiana patient showed changes that might increase the virus’s ability to bind to cells in the human upper respiratory tract—a development concerning to health experts since H5N1 typically targets cell receptors found in birds and other animals, not humans.
- A similar variant appeared in a hospitalized teenager in British Columbia in November. This version also contained mutations that could help the virus target human cells more effectively and cause severe illness.
- A November study of H5N1 from an infected farm worker found a mutation that promotes replication in mammals, allows transmission through airborne droplets, and has proven lethal in laboratory animals.
Infectious disease experts say no evidence exists that human-to-human transmission has occurred yet, even from severely ill patients.
As scientists track viral changes, pharmaceutical companies are racing to develop protective measures against H5N1 bird flu using advanced technologies.
Treatment options for bird flu are also advancing. A new oral antiviral drug from Traws Pharma has proven safe and effective in fighting resistant flu viruses in initial human trials. The company plans to begin larger clinical trials this year.
Should We Be Concerned?
While vaccines and treatments advance, public health officials and researchers are closely monitoring indicators that could signal H5N1’s progression toward pandemic potential, including viral mutations and spread between people. At present, no evidence of human-to-human transmission has occurred and the risk to the general public is believed to be low.
However, experts remain concerned that H5N1 could combine with human influenza viruses to create a version that spreads more easily among people—a risk that increases as seasonal flu activity rises and more people come into contact with infected animals. They warn that while there are currently no signs of unusual flu activity, it’s critical to be vigilant because of the unpredictability of emerging infectious diseases.
To protect against these risks, the CDC advises the public to avoid raw milk products and contact with sick or dead animals.
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