Science Friday
Hosted by Flora Lichtman
As local reports of dead birds rise, the greatest human risk continues to fall on some of the most vulnerable: farm workers.
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Hey, it's Flora Lixman and you're listening to Science Friday. Remember last winter when we were hearing a lot about bird flu?
There are new fears in this country about the potential impact of the H5N1 bird flu on humans.
It was concerning because there were confirmed cases in people and outbreaks in dairy cows and other mammals. But this year, besides sporadic local reports of dead birds, the story seems to have flown off the national news radar. So is not that much news actually good news? And how closely are we tracking bird flu after Doge cuts? Here with the fly overview is Dr. Seema Loktawala, co-director of the Center for Transmission of Airborne Pathogens and an associate professor at Emory University in Atlanta. Seema, thanks for being here.
Thanks for having me.
Give us a status report. Where are we with bird flu this year?
Yeah, I think, as you've mentioned, we don't have a lot of reporting happening, but it is still very prevalent, especially in backyard poultry, poultry farms, and in migratory bird populations. If anybody just Googles "bird flu," you will get a variety of headlines of, you know, vultures falling dead, or geese, or fears of outbreaks in elephant seals in California. But what we aren't seeing is a lot of information anymore about dairy cattle. But we should all be concerned again about egg shortages. You know, states are culling millions of birds to try to still contain this outbreak in poultry farms. That's ongoing.
And, you know, that interface is continuing. The virus is continuing to circulate in the U.S. It has not gone away.
Okay. I mean, to what degree is the federal government tracking bird flu? Do we know?
I think it's hard to know, you know, before with the cattle outbreak, we had a lot of, you know, surveillance efforts ongoing from the USDA and many others. Now that there aren't as many cases reported in cattle and most of it's in migratory birds, it's hard to know the extent of how much H5N1 or bird flu is traveling in these migratory flyways. We do know that when chicken poultry farms get infected, because birds like poultry and chickens act sick, so we can detect it really quickly. And then you have millions of animals that then have to be sacrificed to contain the
spread of the virus on that farm such that you're not devastating the entire farm. So it is still happening. The frequency of detections may be lower unless it's in poultry markets. That doesn't necessarily mean it's not there. One of the things that I would love to know more about is whether the USDA, the frequency of which it's still doing its milk testing program, whether we're still getting H5N1 in dairy cattle milk in the absence of symptoms. We know that a lot of cows are not feeling sick anymore. They're not having the same level, at least in the cattle industry, that they were seeing a year ago.
Oh, that's interesting. So the sim- there are fewer symptoms in cattle this year?
Because there's not a lot of testing of cattle at an individual level, right? So it's hard to know which cows have H5N1. What we do know, though, is that some farms are still testing positive in places like California and others. And Wisconsin had an outbreak in December this past year that was detected by the milk testing programs, but there aren't as many sick cows, right? So previously, bird flu in a cow was combined with other mastitis, which is like chunky, yogurty-looking milk, and as well as a drop in milk production. And so cattle farmers immediately started to notice an impact of bird flu in their production.
That doesn't seem to be happening anymore. We're seeing maybe more mild symptomatic or, you know, non-clinical cows that are infected that are continuing to shed the virus so that the milk is testing positive, but the symptoms aren't there.
What about dairy workers? I mean, I know that was a big concern last year. Are people getting sick with bird flu?
A lot of these individuals, both poultry farms and dairy farms, which have a lot of exposure to these viruses from these animals, are at high risk. What we found last year and through the course of this outbreak is that most of these presentations are mild in individuals, right? It's combined with conjunctivitis, mild influenza respiratory symptoms. We just came off of, you know, a pretty big influenza season, right? If you remember, November, December, lots of flu infections.
We remember, Seema.
That's right. So, so a lot of people are probably having, experiencing flu symptoms, but they don't necessarily go and get tested for flu. Everyone knows it, they just assume it, and you don't have to seek attention, medical attention. And unless we catch a test for a flu strain that is not a human seasonal flu strain, it does not get documented at the level of the CDC.
Okay. I mean, also, we've reported on this, on this show, that, you know, for immigrant populations, there's a disincentive to go get healthcare if you're worried about getting rounded up by ICE, for example.
That's right. And if you have mild respiratory symptoms and conjunctivitis, and you're still able to go to work or stay home for a day and then feel better, maybe you don't seek medical care.
There have been very few confirmed deaths in people from bird flu. When they have occurred, do we know how they were caused? What was the entryway?
Yeah, most of them have been caused by backyard poultry or direct contact with birds, either through handling of sick birds or being in close contact with them.
You know, I know you have a pre-print out on Bio Archive, looking at virus in the air and water. Do I have that right?
That's right.
Can you give us a top-level view?
I can. So, we were very fortunate and worked closely with, you know, the Milk Producers Council in California and the California Department of Food and Agriculture to get on a number of dairy farms, my group and Jason Lombard's team, and look at where the virus is on these dairy farms. And in particular, you know, we study how viruses move through the air. And so, we were really interested in the air, as well as these manure lagoons, which sound really gross. But like, if you're collecting milk from a sick cow, that milk has to get disposed of on a farm. And sometimes, they feed it to the calves. But most of the time, they pour it down into their waste streams. And those waste streams do not come into our, like, waste streams. They're separate. They're collected separate into something known as
a manure lagoon. And these water sources are used as watering holes for birds that are migrating. They're used to irrigate farmland. They're used to clean out barns, etc. And so, what we found was not only did we detect, you know, viral RNA, right? We just talked about like, how you can detect viral RNA in milk. No, we detected an infectious virus in the air and on, in the manure lagoons.
Wow. You did not tell us about manure lagoons last time. I'm certain I would remember.
Yeah, it has become an eye-opening experience, the manure lagoons.
Could wild birds get infected from a manure lagoon?
Potentially, yeah. We found infectious virus in the manure lagoons. They're very big. We do think the milk sort of stabilizes the virus. And so, it may be retaining some infectivity in like, the fat that sort of stays at the top of manure lagoons. It is feasible, right? Because in migratory birds, H5, most bird flu viruses are fecal-oral. So, they drink the water. You know, they sort of are like, you know, maybe even taking it up in their cloaca. And so, all of these routes may be feasible when they come and stop at a manure lagoon.
Oh, my God, fecal-oral. We're really in it right now, Seema. We're deep, we're in deep right now. We have to take a break so I can process that deep dive. But don't go away because we're going to talk about wild birds. You know, bird flu's been around for decades. What is different now? Stay with us.
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Bird flu has been around in birds circulating since the 90s. I remember back when we were getting those reports. Is it different now and how?
It is different now because we've never had this level of detection in the US. So yes, there has always been bird flu, particularly in Southeast Asia and those flyaways that sort of permeate in mainland China, in Vietnam, Cambodia. Those are areas that have always had a recurrence of H5 and bird flu. The extent to which the virus has now spread across multiple different migratory flyways, such that we then found it, of course, in Europe. And then all of these streams, right? They come together quite, you know, robustly in different areas of these little pockets of where birds, you know, can interact with each other.
And so now there have been lots of introductions into the US, both from the Pacific and the Atlantic flyways. And so we have never had to contend with that. Back when we had a few poultry outbreaks, prior to this outbreak, they sort of were contained in poultry and there were just, you know, very modest spillovers. But now we're seeing an extensive amount of viruses in these migratory birds that don't get very sick. Some of them do, right? This is when we were worried about the condors, if you remember, in California. But the fact that it's so prevalent is very concerning. And we should all be concerned about that because then that means it's always going to be a problem that our poultry workers and our poultry industry is going to have
to contend with, as well as the dairy industry and backyard poultry farms. Anybody who has a backyard flock of chickens or turkeys, you should be concerned.
This year, we're also seeing a big outbreak of bird flu in sea lions, right?
Yeah, these aquatic mammals are really interesting, right? Seals and sea lions, both in the coast of South America as well as here in California. There's a lot of aquatic mammals that are becoming infected. And that's because the interface between migratory birds and aquatic mammals is really high. And we don't really understand how many interactions these animals have, how close they are. But all of that can be concerning, and we think that's the route of transmission. Of course, what happens then is people want to go and see sea lions and seals on beaches. Or they're taking care of them, right? Because they're sick and these are mammals. And so the interface within humans becoming infected is high.
Do we have a bird flu vaccine for poultry, for example?
Yes, I think there's a number of different bird flu vaccines that have been developed for poultry purposes specifically.
Do you see any interest or evidence that those are going to be rolled out? What would it take to start using them?
I mean, I think this is sort of a really interesting question, right? Both for not just poultry, right? We can talk about cattle, like places where we think we should be concerned about the human animal interface. Things that concern me are that the more we let these viruses circulate in the wild, the more opportunity we give them to change and evolve and adapt to become successful in humans. And so we should be concerned about all of the animals, poultry included, pigs and cows that humans are known to have a really robust relationship with, right? These are concerning domestic animals because humans interact with them all the time. Why we haven't?
We are a really scientifically advanced society. We can develop vaccines for all sorts of emerging pathogens. We have swine influenza vaccines for other subtypes. We could develop cattle vaccines easily.
It is a question not of development of something that could be useful. It is a question of appetite to implement them.
Do farmers have an appetite to implement them?
Oh, I absolutely think so. I, you know, I think the cattle industry definitely, when they were having a huge production drop and having to kill their animals or send them to beef, or they didn't know which animals were infected. I mean, the number of farmers that said to me, like, if I could know which cows were infected, I would remove them from my farm because they also didn't want the virus spreading amongst their cows. I bet you any poultry farmer is absolutely mortified that they have to kill millions of chickens to just contain the outbreak. And so, yeah, they're getting reimbursed from the USDA, but it's still not a useful business strategy.
So absolutely, I think they would want to implement something that would prevent them from these economic losses.
Okay, so last time we had you on, which was early last year, January 2025, this was right after the first reported death in a person from bird flu in the US. And we asked you what your level of concern was about this becoming a pandemic. And you basically said moderate, you know, you were a moderate level of concern. Where are you today?
I'm still moderate and mostly because I don't think we're doing enough to contain the outbreak. Like I just mentioned, we have the ability to start to implement strategies to reduce this virus spilling over into poultry, pigs and cows. It's not in pigs yet, right? But we're lucky for that because it doesn't mean it doesn't, it's not trying. And the more it tries, the more viruses can be successful. We are letting this virus have a thousand shots on goal every day. And so maybe it takes one in a billion to finally make it a pandemic. But we're letting it have that opportunity. And that's my concern.
What's holding us back?
I think last year I would have said, what's holding us back is that we are very fragmented in the way that we can do implementation of interventions. Right? So I learned a lot of things since this outbreak emerged in 2024. And what I learned that was surprising to me and maybe to others is that the USDA and the CDC cannot make requirements of commercial businesses. But those state departments of agriculture can make requirements of businesses within their state.
Right? U.S. federal government regulations apply to things moving across state lines or at the federal level. They cannot say to you, farmer X, now you have to abide by this, regardless of whatever state legislation there is. But the states can do that. And so I think for the cattle industry, I think this is in their rearview mirror. They're not as concerned anymore about bird flu.
I'm sure the poultry industry is very concerned, and I am sure the swine industry is just holding its breath, hoping it does not impact them. But what we should be doing is being more proactive such that we don't have to be reactive, which would include lots of different implementation of interventions. Things that reduce the spread of viruses on cattle farms, right? Things that we found in our preprint study of ways to mitigate where the virus is on these farms, thinking about how to implement the same sort of strategies in poultry farms, filling out where the virus is and ways to stop its spread, as well as implementation
of vaccines, PPE for individuals working with them, more knowledge for people with backyard poultry farms. I don't think everybody realizes how much bird flu there is in North Carolina, in Pennsylvania, in, you know, California, Texas, Georgia, wherever. Like, it is almost everywhere.
Combination, it sounds like, of education and political will.
Yeah. Isn't it always that, though?
That's it. It's always that. That's always the answer. I don't know why I ask.
The other thing to note is that if you're walking around in the summertime now going to parks and things and you see a dead bird, please do not touch it. Do not let your children touch it. You should call animal control. You can put on appropriate PPE and that would include not just gloves, but also something that's like a respiration, like a mask.
Don't put on your PPE. Call a professional.
Yes. But just don't touch any dead birds, please.
And what about raw milk, as long as we're doing news you can use?
Please don't drink raw milk. You know, Louis Pasteur, he did us all a really great service.
Yeah. Pasteurization is our friend. Seema, thank you for filling us in. I appreciate it.
Of course. Anytime. Thanks for having me, Flora.
Dr. Seema Lakshmiwala is the co-director of the Center for Transmission of Airborne Pathogens and an associate professor at Emory University in Atlanta. This story was published with the assistance of the Journalism and Women's Symposium Health Journalism Fellowship, supported by the Commonwealth Fund. This episode was produced by Kathleen Davis. Thank you so much for listening. And if you have a question or a lead you'd like us to look into, 877-4-CY-FRY is our number. Thanks for listening. I'm Flora Lichtman.
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