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Dear Aventine Readers,
If you think about bird flu, what probably comes to mind is the spike in egg prices a few years ago when millions of U.S. chickens became infected. While bird flu may have slipped from the headlines, it hasn’t stopped worrying scientists who are concerned that the virulent H5N1 strain could mutate to make human-to-human transmission possible. We talk to five experts about what a bird flu pandemic might look like and what it would take to produce a vaccine.
Plus:
The Future of Bird Flu
During the past three years, the avian influenza virus H5N1 — widely known as bird flu — tore through the US poultry industry, causing massive disruptions and driving up the price of eggs. More than 166 million chickens have either died or had to be culled because of the virus since the initial outbreak. After infections began to drop this year, the Centers for Disease Control declared an end to the emergency in July 2025 and news of bird flu slipped from the headlines.
But the crisis isn’t over.
H5N1, which was first identified in the 1990s, surprised scientists during the recent pandemic with its ability to jump to mammals, including cattle, and to infect people. Now, as the potential for another outbreak grows — like other viruses, bird flu flourishes in colder temperatures — virologists and vaccine makers are worried that the virus could mutate so that it’s transmitted among people, potentially leading to a pandemic.
After first being detected in the United States in 2022, H5N1 quickly spread through the wild bird population, causing massive die-offs of geese, ducks, northern gannets and raptors like bald eagles, which feed on the carcasses of infected birds. From wild birds, the virus jumped to commercial and backyard chickens. In 2024, bird flu spilled over into cattle in Texas, a transmission that caught many scientists off guard. It was only after barn cats started dying in large numbers that virologists began to suspect that cows’ milk might be infected.
Another surprise: After the spillover, cows began infecting one another with H5N1 and the outbreak spread across the country. It also spread to humans. As of this writing, 70 people are known to have been infected with the virus and there has been at least one fatality. Almost all the infected patients worked or were exposed to cattle and there’s no evidence yet of sustained human-to-human infection.
The good news is that the food supply is considered safe. The infection often stops chickens from laying eggs, then kills them quickly. Infected cattle still produce milk but pasteurization inactivates the virus. Unpasteurized milk is still a threat: An FDA study last year found infectious H5N1 in 14 percent of the unpasteurized milk it sampled.
Right now, bird flu does not easily spread to people but, like all flu viruses, it can mutate. H5N1 is a segmented virus, meaning that its genetic material is separated into sections. Segmented viruses can combine with other viruses in a process called reassortment. For example, if a person had both bird flu (from proximity to livestock or infected birds) and regular seasonal flu at the same time, the genetic material could be reassorted into a new virus that would have features of both.
For that reason, many scientists believe it’s a question of when and not if there will be sustained person-to-person transmission. Three of the biggest influenza epidemics in the last century resulted from reassortments.
It’s impossible to predict how lethal an H5N1 pandemic could be. Bird flu can cause a massive immune response in human hosts — many times greater than from seasonal flu — potentially leading to pneumonia or organ failure. The World Health Organization has estimated that around half of all people infected die from the disease but there is no way of knowing how many mild cases weren’t detected. Nor can scientists explain why only one person out of 70 infected in the US has died. One theory is that exposure to the 2009 H1N1 pandemic may confer some immunity from H5N1.
In case of an outbreak, traditional vaccines would take about six months to develop, just as they do for seasonal influenza. Using messenger ribonucleic acid (mRNA), the process that produced the most effective Covid-19 vaccines, could potentially cut the development period in half and provide a more robust defense, according to some scientists.
We reached out to five experts on bird flu to find out what lessons we have taken — or that we should take — from the last outbreak, how to reform our agricultural practices, how an outbreak might affect the economy and what is the likelihood of a full-blown human pandemic.
How H5N1 Might Jump to Humans
“The virus and some of its gene segments have undergone significant adaptation in the poultry respiratory tract, making it more adept at jumping species. It’s challenging to pinpoint the exact changes that will be necessary [for sustained person-to-person transmission], but our dogmatic perspective on the problem suggests that a change in the virus’s ability to recognize sialic acid in the respiratory tract of humans is one of the conditions required for the virus to transmit.
Preliminary data from our lab indicates that the virus’s ability to infect human airway cells via respiratory droplets is severely limited. Yes, the virus could potentially target receptors in the respiratory tract, making it more effective. However, predicting the exact level of virulence is highly complex, as it depends on various factors.”
— Daniel Perez, a professor in the Department of Population Health at the College of Veterinary Medicine, University of Georgia
What Are the Chances Bird Flu Becomes a Human Pandemic?
“If you look back in history, flu pandemics happen regularly so we're going to have another flu pandemic. It's based on history and it's also based on the fact that the virus evolves. What we typically see is a virus that starts off as an animal virus, gains abilities to spread between people and that's what triggers a pandemic. So H5N1 checks those boxes: It's an animal virus that is gaining new abilities
It would need to gain the ability to spread between people and it can do that in two ways. Either it mutates to do that and it's shown the abilities to mutate. We have different receptors in our lungs than birds and so it's shown its ability to adapt, but it's still not particularly good. But I just think the more likely way that a pandemic would occur is for [H5N1] to swap genes with another flu virus that's capable of doing that already, like a seasonal virus.”
— Jennifer Nuzzo, a professor of epidemiology and director of the Pandemic Center at the Brown University School of Public Health
What a Human Pandemic Might Look Like
“We missed the potential for H5N1 to infect cattle, especially in the mammary tissue. This is still a large gap in our knowledge of how this happened.
There are many possibilities for emergence of human-to-human transmissible H5N1. I am particularly concerned about H5N1 reassorting with human seasonal H1N1 or H3N2 viruses to gain the properties important for transmission. There are already examples of variants in nature that H5N1 has the potential to broaden or alter its receptor preference.
These viruses could become more virulent, but the interesting thing is that the human cases so far have largely been mild, likely due to preexisting immunity to human seasonal H1N1 strains. A change in receptor preference is unlikely to alter that.”
— Seema Lakdawala, an associate professor and co-director for the Center for Transmission of Airborne Pathogens at Emory University School of Medicine
Vaccines and the Promise of mRNA
“The usual flu vaccine isn't an activated virus. They grow the virus in eggs, then kill it and put that into a vaccine. What RNA has — instead of taking the protein from the virus — it takes the genetic code of the protein and puts it into an mRNA that's delivered.
When you give a mRNA, the cells make thousands if not tens of thousands of copies of that protein. There's a huge amplification. The big difference is it makes a much more potent immune response. If the [virus] mutates, you still have protection. You don't get that with an activated virus. It's incredibly fast. We make personalized cancer vaccines in four to six weeks. The bird flu could probably be made in a few months
The one thing that hasn't happened yet is the [bird flu] mutation to allow human-to-human transmission. When that occurs, we're going to have a new pandemic. We’re really not prepared at all because the government is pulling back on respiratory virus vaccines using mRNA. So we are really unprepared.”
— Drew Weissman, a professor of medicine at the Perelman School of Medicine at the University of Pennsylvania, director of the Penn Institute for RNA Innovation and co-winner (with Katalin Karikó) of the 2023 Nobel Prize in Medicine for his contributions to the mRNA vaccine for Covid-19
Food Supply and Safety
The structure of our food system can magnify risks. In the US, we rely on large, highly concentrated operations and supply chains. This scale of production is efficient, but when disruptions hit, the impacts can spread quickly. During Covid, we saw this with bottlenecks in meat processing, where just a handful of plants handle a large share of production. With bird flu, we’re seeing similar vulnerabilities in poultry and dairy, where concentrated herds and flocks make the system more exposed. By contrast, countries like Canada, with smaller and more dispersed operations, haven’t experienced the same scale of disruption.
We need to build more resilience into the food system. That means strengthening biosecurity, investing in early warning systems, and making supply chains more flexible when shocks hit. Diversifying production, geographically and by scale, can help reduce risks, but it requires trade-offs. More critically, we need to seriously consider all options available, including vaccines for livestock against bird flu to help stop the spread of the virus and avoid the kind of cascading effects we’ve been seeing.”
— David Ortega, a professor and the Noel W. Stuckman Chair in Food Economics & Policy at Michigan State University-
Magazine and Journal Articles Worthy of Your Time
The death rays that guard life, from Works in Progress
3,600 words, or about 15 minutes
Clean drinking water is a key pillar of public health. Clean air could be, too. Obviously it isn’t possible to clean all the air around us, but in areas where there are high concentrations of people — schools, offices, shops — an underused technology makes it possible. Instead of relying solely on expensive ventilation systems or bulky filters, researchers are exploring germicidal ultraviolet light as a means of killing pathogens in the air. The concept isn’t new: UV light was first used to kill microbes in the late 19th century, but concerns about skin irritation and inconsistent results stalled its adoption. Now, a safer variant called far-UVC has revived interest. One 2024 study found that far-UVC lamps can reduce airborne viruses by 98 percent, equivalent to cycling a room’s air 36 times per hour. So why isn’t it everywhere? Large-scale trials are scarce, partly because it’s hard to isolate how people are exposed to pathogens outside treated spaces, which makes it difficult to assess the technology’s effectiveness. But early adopters — including Mount Sinai Hospital — are testing it in real-world settings. If further research backs the early promise, far-UVC could one day make clean air a public health standard that is as fundamental as clean water.
Unlocking a Million Times More Data for AI, from The Institute for Progress
3,100 words, or about 13 minutes
The idea that AI is hitting a wall because we’re running out of data to train it on has become a common refrain. But that’s not exactly true. The largest AI models today are trained on no more than 180 terabytes of text and images, yet the world contains an estimated 180 zettabytes of digital information, roughly a billion times more. So the problem isn’t scarcity, but access. And for good reason: A lot of this data — from medical records and financial transactions to proprietary research and customer databases — is locked away to ensure privacy. This report explores how such data might be unlocked without compromising the owner’s privacy or control. One part of the solution, known as a mixture of experts, partitions AI models so that specific types of data are used to train specific functions, as agreed upon by data owners. Another involves ensuring that the hardware used for training can keep data encrypted as it’s transferred and processed on secure chips. Both technologies exist today. What’s missing is an effort to deploy them at scale — and the report argues that DARPA, or a similarly capable government agency, may be uniquely positioned to lead that push.
Reimagining School In The Age Of AI, from Noema
3,400 words,or about 14 minutes
Earlier this year, we explored how educators could — and should — use AI, with a particular focus on AI tutors. This new essay pushes that idea further. Greg Easley, a technologist and adjunct professor at The New School in New York City, imagines an education system where AI tools don’t just personalize lessons but design entire, evolving curricula for each student. “Instead of following a fixed curriculum, the app would dynamically construct your learning path,” he writes. “This would enable a non-linear learning map that evolves in real time, tailored to the student’s unique progress and needs.” Teachers, meanwhile, would focus more on “orchestrating personal growth” and “helping [students] understand how to learn.” The approach raises plenty of questions, from how grading would work to whether such a system could be equitable. But it’s a provocative look at how AI could reshape education if taken to one of its more radical logical conclusions.