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From The New York Times, I'm Sabrina Tavernisi, and this is The Daily. The outbreak of bird flu that is tearing through the nation's poultry farms is the worst in US history. But scientists say it's now starting to spread into places and species it's never been before. Today, My colleague, Emily Anthes, explains. It's Monday, April 22nd. Emily, welcome back to the show.

Thanks for having me. Happy to be here.

Emily, we've been talking here on Daily about prices of things and how they've gotten so high, mostly in the context of inflation episodes. One of the items that keeps coming up is eggs. Egg prices were through the roof last year, and we learned It was related to this. Avian flu has been surging in the United States. You've been covering this. Tell us what's happening.

Yeah, so I have been covering this virus for the last few years, and The bird flu is absolutely tearing through poultry flocks, and that is affecting egg prices. That's a concern for everyone, for me and for my family. But when it comes to scientists, egg prices are pretty low on their list of concerns because they see this bird flu virus behaving differently than previous versions have. They're getting nervous in particular about the fact that this virus is reaching places and species where it's never been before.

Okay, so bird flu, though, isn't new. I remember hearing about cases in Asia in the '90s. Remind us how it began.

Bird flu refers to a bunch of different viruses that are adapted to spread best in birds. Wild water birds, in particular, are known for carrying these viruses. And flu viruses are famous for also being shapeshifters. So they're constantly swapping genes around and evolving into new strains. And as you mentioned back in the '90s, a new version of bird flu, a virus known as H5N1, emerged in Asia, and it has been spreading on and off around the world since then, causing periodic outbreaks.

And how are these outbreaks caused?

So wild birds are the reservoir for the virus, which means they carry it in their bodies with them around the world as they fly and travel and migrate. And most of the time, these wild birds, like ducks and geese, don't even get very sick from this virus, but they shed it. So as they're traveling over a poultry farm, maybe if they happen to go to the bathroom in a pond that the chickens on the farm are using or eat some of the feed that chickens on the farm are eating, they can leave the virus behind. And the virus can get into chickens. In some cases, it causes mild illness. It's what's known as low pathogenic avian influenza. But sometimes the virus mutates and evolves, and it can become extremely contagious and extremely fatal in poultry.

Okay, so the virus comes through wild birds but gets into farms like this, as you're describing. How have farms traditionally handled outbreaks when they do happen?

Well, because this threat isn't new, there is a pretty well-established playbook for containing outbreaks. It's sometimes known as Stamping Out. And brutally, what it means is killing the birds. So the virus is so deadly in this highly pathogenic form that it's destined to kill all the birds on a farm anyway once it gets in. So the response has traditionally been to proactively depopulate or cull all the birds so it doesn't have a chance to spread.

So that's pretty costly for farmers.

It is, although the US has a program where it will reimburse farmers farmers for their losses. The way these reimbursements work is they will reimburse farmers only for the birds that are proactively culled and not for those who die naturally from the virus. The thinking behind that is it's a way to incentivize farmers to report outbreaks early.

Okay, lots of chickens are killed in a way to manage these outbreaks, so we know how to deal with them. But what about now? Tell me about this new strain.

This new version of the virus, it emerged in 2020. After the deadly outbreak of the novel coronavirus, the authorities have now confirmed an outbreak of the H5N1 strain of influenza, a bird flu. And pretty quickly it became clear that a couple of things said it apart.

A bald eagle found dead at Carvin's Cove has tested positive for the highly contagious bird flu.

This virus, for whatever reason, seemed very good at infecting all sorts of wild birds that we don't normally associate with bird flu. He was stepping and then falling over and using its wing to ride itself. Things like eagles and condors and pelicans. We've just lost a parliament of owls in Minneapolis. Yeah, a couple of high-profile nests. Also in the past, wild birds have not traditionally gotten very sick from this virus. This version of the virus not only spread widely through the wild bird population, but it proved to be devastating.

They're washing up along the East Coast of the country, from Scotland down to Suffolk.

We were hearing about mass die-offs of seabirds in Europe by the hundreds and the thousands.

And the bodies of the dead dot the island wherever you look. Wow. Okay, so then, as we know, this strain, like previous ones, makes its way from wild animals to farmed animals, namely to chickens. But it's even more deadly.

Absolutely. In fact, it has already caused the worst bird flu outbreak in US history. More than 90 million birds in the US have died as a result of this virus.

90 million birds?

Yes. I should be clear that that represents two things. So some of those birds are birds who naturally got infected and died from the virus. But the vast majority of them are birds that were proactively cold. What it adds up to is 90 million farmed birds in the US have died since this virus emerged. And it's not just a chicken problem. Another thing that has been weird about this virus is it has jumped into other kinds of farms. It is the first time we've seen a bird flu virus jump into US livestock. It's now been reported on a number of dairy farms across eight US states, and that's just something that's totally unprecedented.

It's showing up at dairy farms now. You're saying that bird flu has now spread to cows. How did that happen?

We don't know exactly how cows were first infected, but most scientists best guess is that maybe an infected wild bird that was migrating shed the virus into some cattle feed or a pasture or a pond, and cattle picked it up. The good news is they don't seem to get nearly as sick as chickens do. They are generally making full recoveries on their own in a couple of weeks.

Okay, so no mass calling of cows.

No, that doesn't seem to be necessary at this point. But the bad news is that it's starting to look like we're seeing this virus spread from cow to cow. We don't know exactly how that's happening yet, but anytime you see cow to cow or mammal to mammal transmission, that's a big concern.

Why is Why is that exactly?

Well, there are a bunch of reasons. First, it could allow the outbreak to get much bigger, much faster, which might increase the risk to the food supply. We might also expect it to increase the risk to farm workers, people who might be in contact with these sick cows. Right now, the likelihood that a farmer who gets this virus passes it on is pretty low. But anytime you see animal-to-mammal transmission, it increases the chance that the will adapt and possibly, maybe one day, get good at spreading between humans. To be clear, that's not something that there's any evidence of happening in cows right now. But the fact that there's any cow-to-cow transmission happening at all is enough to have scientists a bit concerned. Then if we think more expansively beyond what's happening on farms, there's another big danger lurking out there. That's what happens when this virus gets into wild animals, vast populations that we can't control.

We'll be right back. Emily, you said that another threat was the threat of flu in wild animal populations. Clearly, of course, it's already in wild birds. Where else has it gone?

Well, the reason it's become such a threat is because of how widespread it's become in wild birds. So they keep reintroducing it to wild animal populations pretty much anywhere they go. So we've seen the virus repeatedly pop up in all sorts of animals that you might figure would eat a wild bird. So foxes, bobcats, bears. We actually saw it in a polar bear, raccoons. So a lot of carnivores and scavengers. The thinking is that these animals might stumble across a sick or dead bird, eat it, and contract the virus that way. But we're also seeing it show up in some more surprising places, too. We've seen the virus in a bottle-nosed dolphin in all places. Wow. And most devastatingly, we've seen enormous outbreaks in other sorts of marine mammals, especially sea lions and seals. So elephant seals, in particular in South America, were just devastated by this virus last fall. My colleague Aporva Mandvili and I were talking to some scientists in South America who described to us what they called a scene from hell of walking out onto a beach in Argentina that is normally crowded with chaotic, living, breathing, breathing elephant seals and the beach just being covered by carcass after carcass after carcass.

God. Mostly carcases of young, newborn pups. The virus seemed to have a mortality rate of 95% in these elephant seal pups, and they estimated that it might have killed more than 17,000 of the pups that were born last year, so almost the entire new generation of this colony. These are scientists that have studied these seals for decades, and they said they've never seen anything like it before.

Why is it so far-reaching, Emily? I mean, what explains these mass die-offs?

There are probably a few explanations. One is just how much virus is out there in the environment being shed by wild birds into water and onto beaches. These are also places that viruses like this haven't been before. It's reaching elephant seals and sea lions in South America that have no prior immunity. There's also the fact that these particular species, these sea lions and seals, tend to breed in these huge colonies all crowded together on beaches. And so what that means is if a virus makes its way into the colony, it's very conducive conditions for it to spread. And scientists think that that's actually what's happening now, that it's not just that all these seals are picking up the virus from individual birds, but that they're actually passing it to each other.

Basically, this virus is spreading to places it's never been before, virgin snow territory, where animals just don't have the immunity against it. Once it gets into a population packed on a beach, say, of elephant seals, it's just like a knife through butter.

Absolutely. An even more extreme example of that is what we're starting to see happen in Antarctica, where there's never been a bird flu outbreak before until last fall, for the first time this virus reached the Antarctica mainland, and we are now seeing the virus move through colonies of not only sea birds and seals, but Penguin colonies, which have not been exposed to these viruses before. It's too soon to say what the toll will be, but penguins also, of course, are known for breeding in these large colonies, probably don't have many immune defenses against this virus, and, of course, facing all these other environmental threats. There's a lot of fear that you add on the stress of a bird flu virus, and it could just be a tipping point for penguins.

Emily, at this point, I'm wondering why more people aren't talking about this. I didn't know any of this before having this conversation with you, and it feels pretty worrying.

Well, a lot of experts and scientists are talking about this with rising alarm. In terms that are quite stark. They're talking about the virus spreading through wild animal populations so quickly and so ferociously that they're calling it an ecological disaster. But that's a disaster that sometimes seems distant from us, both geographically. We're talking about things that are happening maybe at the tip of Argentina or in Antarctica, and also from our concerns of our everyday lives. What's happening in penguins might not seem like it has a lot to do with the price of a carton of eggs at the grocery store. But I think that we should be paying a lot of attention to how this virus is moving through animal populations, how quickly it's moving through animal populations, and the opportunities that it is giving the virus to evolve into something that poses a much bigger threat to human health.

The way it's spreading in wild animals, even in remote places like Antarctica, that's important to watch, at least in part because there's a real danger to people here.

We know that the virus can infect humans, and that generally it's not very good at spreading between humans. But the concern all along has been that if this virus has more opportunities to spread between mammals, it will get better at spreading between them. That seems to be what is happening in seals and sea lions. Scientists are already seeing evidence that the virus is adapting as it passes from marine animal to marine animal, and that could turn it into a virus that's also better at spreading between people. If somebody walks out onto a beach and touches a dead sea lion, if their dog starts playing with a sea lion carcass, you could imagine that this virus could make its way out of marine mammals and into the human population. If it's this mammalian adapted version of the virus that makes its way out, that could be a bigger threat to human health.

So the sheer number of hosts that this disease has, the more opportunity it has to mutate, and the more chance it has to mutate in a way that would actually be dangerous for people.

Yes, and in particular, the more mammalian hosts. So that gives the virus many more opportunities to become a specialist in mammals instead of a specialist in birds, which is what it is right now.

Right. I like that, a specialist in mammals. So what can we do to contain this virus?

Well, scientists Scientists are exploring new options. There's been a lot of discussion about whether we should start vaccinating chickens in the US. The government, USDA labs, have been testing some poultry vaccines. It's probably scientifically feasible. There are challenges there, both in terms of logistics, just how would you go about vaccinating billions of chickens every year? There are also trade questions. Traditionally, a lot of countries have not been willing to accept poultry products from countries that vaccinate their poultry. There's concern about whether the virus might spread undetected in flocks that are vaccinated. As we saw with COVID, the vaccine can sometimes stop you from getting sick, but it doesn't necessarily stop infection. Countries are worried they might unknowingly import products that are harboring the virus.

What about among wild animals? I mean, how do you even begin to get your head around that?

Yeah, I mean, thinking about vaccinating wild animals maybe makes vaccinating all the chickens in the US look easy. There has been some discussion of limited vaccination campaigns, but that's not feasible on a global scale. Unfortunately, the bottom line is there isn't a good way to stop spread in wild animals. We can try to protect some vulnerable populations, but we're not going to stop the circulation of this virus.

Emily, we started this conversation with a curiosity that the Daily had about the price of eggs. Then you explained the bird flu to us, and then somehow we ended up learning about an ecological disaster that's unfolding all around us and potentially the source of the next human pandemic. That is pretty scary.

It is scary, and it's easy to get overwhelmed by it. I feel like I should take a step back and say, none of this is inevitable. None of this is necessarily happening tomorrow. But this is why scientists are concerned and why they think it's really important to keep a very close eye on what's happening both on farms and off farms as this virus spreads through all sorts of animal populations. One thing that comes up again and again and again in my interviews with people who have been studying bird flu for decades is how this virus never stops surprising them. And Sometimes those are bad surprises, like these elephant seal die offs, the incurusions into dairy cattle. But there are some encouraging signs that have emerged recently. We're starting to see some early evidence that Some of the bird populations that survived early brushes with this virus might be developing some immunity. So that's something that maybe could help slow the spread of this virus in animal populations. We just We don't entirely know how this is going to play out. Flu is a very difficult, wily foe, and so that's one reason scientists are trying to keep such a close, attentive eye on what's happening.

Emily, thank you.

Thanks for having me.

We'll be right back. Here's what else you should know today. On this vote, the Yeiser 366 and the Yeiser 58, the bill is passed. On Saturday, in four back-to-back votes, the House voted resoundingly to approve a long-stalled package of aid to Ukraine, Israel, and other American allies, delivering a major victory to President Biden, who made aid to Ukraine one of his top priorities.

On this vote, the yays are 385 and the nos are 34, with one answering present. The bill is passed without objection.

The House passed the component parts of the $95 billion package, which included a bill that could result in a nationwide ban of TikTok.

On this vote, the yays are 311 and the nays are 112. The bill is passed. One voting present.

I missed it, but thank you. In a remarkable breach of custom, Democrats stepped in to supply the crucial votes to push the legislation past hardline Republican opposition and bring it to the floor.

The House will be in order Sure.

The Senate is expected to pass the legislation as early as Tuesday. Today's episode was produced by Ricky Nowetzky, Nina Feltman, Eric Krupke, and Alex Stern. It was edited by Lisa Chou and Patricia Willings. Contains original music by Marion Lozano, Dan Powell, Ron Nemistow, and Sophia Landman, and was engineered by Chris Wood. Music is by Jim Brunberg and Ben Lansberg of WNDY. Special thanks to Andrew Jacobs. That's it for The Daily. I'm Sabrina Tavernisi. See you tomorrow.