Tracking Emerging Public Health Challenges – November 23, 2025 – Bird Flu
“The first human to have ever been infected with the H5N5 strain of bird flu has died, Washington state health officials confirmed late Friday.
The person was an older adult with underlying health conditions, the Washington State Department of Health said in a news release.
The person had a backyard flock of mixed domestic birds. No other details were released out of respect of the family’s privacy, health officials said.
There are various types of bird flu strains. The 70 human cases reported in the United States over the past year and a half involved the strain known as H5N1.” (1)
“This particular strain of bird flu, H5N5, had never been seen in a person before. It appeared first in 2023, infecting birds and mammals in eastern Canada.
According to research published last year on the novel strain, some infected animals carried a key mutation in the virus that allows it to transfer more easily between mammals.
Epidemiologists and virologists worry that avian influenza could generate a pandemic if allowed to spread and mutate. For instance, the H5N1 virus circulating in dairy cattle in North America is one mutation away from being able to spread easily between people.
Every time a bird flu virus infects a person, concerns grow that it could change, becoming more transmissible or more deadly. For instance, if a sickened person also has another flu virus replicating in their body, there’s concern the viruses could exchange genetic material. Just by having an opportunity to replicate and evolve millions of times in the human body, it could acquire deadly mutations.” (2)
““The risk to the public remains low,” the statement from state health officials said. “No other people involved have tested positive for avian influenza.”
Health officials said they would monitor anyone who came in close contact with the patient, but “there is no evidence of transmission of this virus between people”.
Earlier this month, the Centers for Disease Control and Prevention issued a statement about the infection that said no information would suggest “the risk to public health has increased as a result of this case”.
H5N5 is not believed to be a greater threat to human health than the H5N1 virus behind a wave of 70 reported human infections in the US in 2024 and 2025. Most of those have been mild illnesses in workers on dairy and poultry farms.” (3)
“There is no doubt that the H5N1 virus also poses a threat to our species, but for this virus to become pandemic, it would need to undergo several changes. These would include an improved ability to spread through the air between humans and to bind to human cell receptors, and a greater capacity to enter our cells and multiply within them. The virus would also need to be able to evade our immune systems.
It is difficult for the right combination of all these mutations to occur, but not impossible. The flu virus is a master of variability, mutation and recombination. Other influenza viruses caused the major pandemics of the 20th century. This means the massive global circulation of the H5N1 virus in the animal world is very bad news indeed.
To preserve human health, it is essential to monitor the animal world. The best way to do this is the One Health approach. This involves improving biosecurity on farms, intensifying veterinary surveillance (not only in poultry but also in cattle and pigs), and promoting effective coordination between the public health and animal health sectors through a collaborative approach. While we are not facing a new pandemic right now, the H5N1 virus is getting closer and closer.” (4)
“After a quiet summer, bird flu is on the move again, and experts say it poses an escalating threat. While the virus doesn’t appear capable of spreading from human to human, it has killed people exposed to sick poultry. This year, the United States saw its first death from bird flu, a Louisiana senior with a flock of backyard chickens.
Viruses are constantly evolving, and if a person catches bird flu while infected with a seasonal flu, the pathogens could mutate into a variant that infects large numbers of people. “The minute it transmits in humans, it’s done,” warned Erin Sorrell, senior scholar at the Johns Hopkins Center for Health Security. “ (5)
1.1st human known to be infected with H5N5 strain of bird flu dies, Washington state officials say, By Youri Benadjaoud, https://abcnews.go.com/US/1st-human-infected-h5n5-strain-bird-flu-dies/story?id=127774354
2.Washington state resident dies of new H5N5 form of bird flu, By Susanne Rust, https://www.latimes.com/science/story/2025-11-21/washington-state-resident-dies-of-new-h5n5-form-of-bird-flu
3.Bird flu: first ever death from rare H5N5 strain is recorded in US, by Associated Press, https://www.theguardian.com/world/2025/nov/22/bird-flu-first-death-h5n5-strain-us
4.H5N1 bird flu cases spike in Europe. How worried should we be?, by Ignacio López-Goñi, https://medicalxpress.com/news/2025-11-h5n1-bird-flu-cases-spike.html
5.What the U.S. Government Is Dismissing That Could Seed a Bird Flu Pandemic, by Nat Lash, https://www.propublica.org/article/bird-flu-airborne-usda-pandemic
curated by Jonathan M. Metsch, Dr.P.H.
Clinical Professor of Environmental Medicine, Icahn School of Medicine at Mount Sinai