Bird flu, feared as a possible pandemic, poses growing risk to people as pathogen spreads, scientists warn

CBS News

20-04-2025

Bird flu has been circling the globe for decades. So the discovery in 2024 that the deadly pathogen had jumped from a wild bird to a cow came as a shock to virus watchers. Now, in just over a year, the virus has ripped through America's dairy herds and poultry flocks. It has jumped to other mammals – including humans. Seventy Americans have caught the virus,
one has died
. Long feared as a possible pandemic, doctors and veterinarians fighting the virus told us Biden's government was slow to act; while the Trump administration has now laid off more than a hundred key scientists – all as the virus keeps spreading.
Dr. Kay Russo: At present, we're given a stick, and they put a blindfold on us, and we're sent into a gunfight and we're losing. We are losing.
Veterinarian Dr. Kay Russo told us we are running out of time to stop bird flu. She was called in when the virus H5N1 hit this dairy herd in Colorado last summer. It cost the farm about $400,000 to treat its sick cattle – most recovered. But as an added precaution, we suited up to ensure we didn't bring anything onto the farm ourselves.
Bill Whitaker: There's no front or back.
Dr. Kay Russo: There's no front or back. It's high fashion.
Bill Whitaker: It's real high fashion.
It's not clear how bird flu is spread from cow to cow, but milking equipment is a prime suspect. The virus is thought to linger on the auto-milker waiting for the next cow. Workers here in milking parlors have also fallen sick.
Bill Whitaker: So what concerns you the most?
Dr. Kay Russo: The pandemic potential for a virus like this one. And you know that is the worst case scenario, right? And ultimately one we want to avoid. I can't say that that's gonna happen but we don't want to play with fire.
It
started in Texas
. In early 2024, cows were suffering from a mysterious disease: their fevers spiked, their milk dried up, they were coughing, drooling, lethargic. Soon there were more sick cattle in neighboring states. Kay Russo joined a conference call of worried vets to try to figure it out.
Dr. Kay Russo: I started asking questions. "What are the birds doing on the farm?" And one of the veterinarians replied, "well, they're all dead."
Bill Whitaker: So they're seeing dead birds on the farms –
Dr. Kay Russo: Yep. Yep. You know we started to see the cats that were demonstrating neurologic symptoms. And--and more alarmingly the workers were complaining of flu-like symptoms.
Tests confirmed Russo's worst fears: H5N1 had jumped to cattle for the first time. In past outbreaks, bird flu has often been deadly in people.
Dr. Kay Russo: If you look at cases worldwide of H5 influenza, the mortality rate's fifty per cent. And so we're all kind of you know, talking to each other. What does this mean? And that was a scary space to be in.
Despite the urgency, Russo and other vets told us the Biden administration was slow to act. It was a month before the U.S. Department of Agriculture required cows to be tested before interstate travel, and 10 months before a raw milk testing program was launched. Today, some states test weekly, some hardly at all.
Bill Whitaker: Do we have enough information about how this virus is spreading?
Dr. Kay Russo: I would say today, no. And that comes down to boots on the ground where you have a strike force that comes in the middle of an outbreak and--and just starts collecting data.
Russo told us at the moment the virus has the upper hand.
Dr. Kay Russo: I think it's a numbers game, and the more we let it move unchecked, the more likely we're gonna have even a bigger mess on our hands.
Poultry farmers have had to kill tens of millions of birds – removing them with trailers – and driving
egg prices
sky high. Now, a new strain of bird flu has been discovered in cattle. It has led to more severe disease in some people.
Dr. Kamran Khan: This is a threat that is very significant and very real. And I recognize also this is a moment where it's easy to sound like an alarmist. What I'm here to tell you is this is a very serious threat to humanity. And the longer we let this persist, the greater the risks are going to be.
Dr. Kamran Khan is an infectious disease physician in Toronto. His company, BlueDot, was among the first to flag the virus in China that became the COVID pandemic. Khan told us bird flu is just as concerning. He showed us how fast the virus has spread among dairy cattle.
Bill Whitaker: This seems like almost a wildfire to me.
Dr. Kamran Khan: Yeah, absolutely.
Now add in poultry outbreaks.
Bill Whitaker: So this is virtually the whole country?
Dr. Kamran Khan: Pretty much.
Next, Dr. Kamran Khan showed us a map of all the confirmed human cases of bird flu in the last five years. Most have been in Asia – until now.
Dr. Kamran Khan: What you start to see around 2024 is you start to see a case in Texas, and then you start to see this sudden, rapid increase in cases across the country.
Bill Whitaker: All over the place.
Dr. Kamran Khan: What's happening here is wild birds have infected cows, who have then infected other cows, who have then infected humans. And so there's this complex web of all of these different animal species now passing the virus in different directions.
Bill Whitaker: Is this one of those things you have never seen before?
Dr. Kamran Khan: The world has never seen this kind of situation and it's showing us that the virus is capable of adaption. If you allow it, it will just get better and better at infecting other mammals, including potentially humans.
Most of the confirmed cases in the U.S. have been farmworkers. Most had mild symptoms. The one person who died had underlying health conditions. The Centers for Disease Control and Prevention say the virus still poses a low risk to the general public. But Khan told us many cases are going undetected.
Bill Whitaker: Why do you say that?
Dr. Kamran Khan: So in a recent study of dairy workers their blood was tested for antibodies to H5N1, not looking for the virus, but looking for the immune system's memory of this virus. And it turns out that 7 per cent of them, one out of roughly every 15 workers actually had antibodies to H5N1.
Bill Whitaker: People are not generally getting very sick from this. So what's the reason for all the alarm?
Dr. Kamran Khan: Influenza is a particularly formidable virus. It is constantly changing. And the more that we allow it to evolve and adapt by infecting people, I mean, this is kinda Darwinian evolution here, right? It can change in ways that actually make it even more deadly, or more easily transmissible, or even resist against some of the antiviral medications that we have.
Khan told us every new infection increases the odds bird flu could lead to severe disease – as we saw during COVID. In North America, six people now have ended up in the hospital with bird flu. More worrying, five people had no known exposure to sick animals.
One girl in Mexico died
two weeks ago.
Dr. Kamran Khan: We are really at risk of this virus evolving into one that has pandemic potential. And the reality is none of us know whether this is next week, or next year, or never. I don't think it's never. But it may be here far sooner than any of us would like.
Many scientists told us vaccines could be our best defense. There is a vaccine for bird flu, but it has not been licensed by the Food and Drug Administration. Moderna has a new one – but the Trump administration has paused its final funding. There are vaccines for poultry too – but they haven't been used because many of America's trading partners will not import vaccinated birds. A glimmer of hope: the USDA's milk testing program.
Dr. Keith Poulsen: This is repurposed from COVID testing from three or four years ago.
Dr. Keith Poulsen is director of the Wisconsin Veterinary Diagnostic Lab, part of the USDA's plan to test raw milk for H5N1. Pasteurization kills the virus, but raw milk can be loaded with it.
Bill Whitaker: Is this where you would identify the virus?
Dr. Keith Poulsen: Yeah. It can detect even just one positive cow in a group of a thousand.
Forty-five states are now doing some form of testing. Poulsen told us it's helped to slow the spread of the virus in some states.
Bill Whitaker: When you see the outbreak curve level off or start to decline, do you go like "Whew. We dodged one?"
Dr. Keith Poulsen: I don't think we go "whew" until we're deactivated, our lab. We're still in outbreak response mode. And while we may have fewer detections, we know that there are still viruses circulating based on all the data from the virologists that's we're talking to. And we want to make sure that we catch it fast.
The CDC is trying to ramp up its testing. But there's another problem: almost half of farmworkers are undocumented and may be reluctant to be tested.
Dr. Angela Rasmussen: If we're not testing people, if we're not looking for people who might get it, if we're not looking for evidence of an early cluster of human-to-human transmission, then we're going to miss it.
Dr. Angela Rasmussen is an American virologist working in Canada. Rasmussen told us it's not just the number of human cases that is alarming, but that the virus is jumping to more mammals. Every new spillover gives the virus another chance to evolve and potentially spread person to person.
Bill Whitaker: So we are now seeing the virus has spread from birds to cattle, and now to foxes, goats, pigs, rats, cats, raccoons–
Dr. Angela Rasmussen: The fact that this virus can infect so many different types of mammals is a huge concern in terms of its ability to infect people.
Bill Whitaker: One of your colleagues told us that if this should spiral into a pandemic, this flu could make Covid look like a walk in the park.
Dr. Angela Rasmussen: I agree.
Bill Whitaker: You're scaring me.
Dr. Angela Rasmussen: I'm scared about it myself. I don't sleep very much these days, Bill.
Rasmussen was among the scientists given expert briefings by the Biden administration in 2024. She told us Biden's team miscalculated the threat at first.
Dr. Angela Rasmussen: It was some gambling and some wishful thinking. Thinking this isn't actually gonna be that big of a deal. And it turns out it was a very big deal.
Bill Whitaker: Has the Trump Administration gotten its arms around this problem?
Dr. Angela Rasmussen: No, I would say is the short answer. But the other-- the longer answer is that I don't actually entirely know what is –what is going on.
Bill Whitaker: Why is that?
Dr. Angela Rasmussen: Many of the people who were working on this, at least at CDC, have--have been fired from the federal government. So the influenza division at CDC has been decimated, and in fact, there is a communications ban that has been put on these federal workers.
Bill Whitaker: -- what do you think of that?
Dr. Angela Rasmussen: I think it's insane, actually, that I have to have conversations on encrypted messaging apps with my colleagues, who I would normally just send emails to.
Hundreds of federal scientists and health workers who track bird flu have been
laid off
. Some may be rehired. The CDC declined to answer our questions, saying it continues to respond to the H5N1 bird flu outbreak. Colorado vet Kay Russo – and others – told us they feel stymied: the current distrust of science and vaccines is hurting their fight to try to prevent the next pandemic.
Dr. Kay Russo: I would scorch the earth if this ends up in children deaths. And so as a mother, as a veterinarian, as a scientist, I'm just asking you, trust us, because I will do everything in my power and there's plenty of folks behind me that will do the same, to keep this from getting to that point.
Produced by Heather Abbott. Associate producer, Matthew Riley. Broadcast associate, Mariah Johnson. Edited by Warren Lustig.