What a Leading Epidemiologist Says You Should Know About the Bird Flu

Michael Osterholm breaks down what the bird flu is, why it’s spreading to dairy cows and the pandemic lessons we failed to learn

Justin Perkins & Joel Bleifuss May 30, 2024

This article was last updated on May 30. For up to date information, check out the CDC’s bird flu information page.

Four years after the World Health Organizations declared the SARS-CoV-2 outbreak a global pandemic—from a novel virus thought to have jumped from wild animals to humans, although its origins remain murky—another virus has emerged as a possible global threat. In March, the avian influenza, or bird flu, was reported to have spread to dairy cows and a farmworker who had been in contact with them.

The Highly Pathogenic Avian Influenza (HPAI) A(H5N1) virus, as the bird flu is known scientifically, has been spreading through the United States since January 2022. So far, the virus has been discovered in more than 9,360 wild birds and has jumped species to more than 220 mammals, mostly carnivores or omnivores that contracted the disease by eating infected birds and mammals.

The virus has infected 486 commercial poultry flocks and 653 backyard flocks in in 48 states. In addition, this year, it has now been found to infect 52 dairy herds in 9 states. And, as of May 22, it has infected 2 humans, one in Texas and the other in Michigan, both of whom worked with dairy herds. [Update: On May 30, a third dairy worker tested positive for bird flu after exposure to infected cows in Michigan, and reported upper respiratory tract symptoms, according to U.S. officials.]

Though the threat to humans remains low, the virus presents many unknowns. Farmworkers, already a vulnerable population lacking adequate workplace protection or employer oversight, remain at the frontlines of the disease. (As of this writing, the 3 reported human cases of bird flu in the U.S. this year have been farmworkers, 2 who have worked with dairy cows and one that worked with poultry).

Barn Raiser sat down with Michael Osterholm, one of the world’s leading epidemiologists and founding director of the Center for Infectious Disease Research and Policy at the University of Minnesota, to discuss what we know and don’t know about the threat bird flu poses to both farmer workers and the general public.

For all the speculation swirling in the media about the avian flu as the harbinger of the next pandemic, Osterholm stresses that it is just as important to understand the ways our public health systems and our society is responding to or ignoring the lessons that should be learned from the Covid 19 pandemic.

Last year, Osterholm and his colleagues from the Biden administration’s Covid-19 transition advisory board wrote an op-ed for the New York Times that detailed 13 lessons the public health community has yet learn from the Covid pandemic. They concluded: “The United States is repeating its panic-and-forget approach to crises.”

In the following interview, Osterholm breaks down what the bird flu is, why it’s spreading to dairy cows, and how public health officials and the media can work to rebuild eroded public trust.

The current situation with the Highly Pathogenic Avian Influenza (HPAI) seems to be evolving in a troubling direction. What is this virus and how is it spread?

First of all, to give some perspective so that people understand, avian influenza viruses have existed in wild aquatic birds long before humans were on the face of the Earth. These birds have receptor sites for the virus in their G.I. tracks. And this is where the virus resides and for eons of time has not had a major negative impact on birds.

As species have evolved, birds continued to have what is called an alpha 2,3 sialic acid receptor site, meaning this is how the virus attaches to the cells in the gut of the bird so that the virus could infect those cells and therefore maintain itself. As humans evolved, we developed another set of receptor sites, in our respiratory tract, called alpha 2,6 sialic acid receptors. This is where the human viruses, the influenza viruses, attach that way. It is very difficult, if not virtually impossible, for an alpha 2,3 virus like the H5N1 bird flu virus to infect somebody that has alpha 2,6 receptor sites. The virus has to change sufficiently to become a human virus. And that’s what we worry about with pandemics.

Now, there are several ways that those viruses can do that. One is called reassortment. That is where a bird virus and a human virus get together in one set of cells in a lung and actually swap out genetic material and create a new virus. That’s exactly what happened in 2009 with the H1N1 flu virus. It turned out that, in fact, human and bird viruses got together in swine operations in Mexico, and out came a new H1N1 that caused that pandemic. Reassortment can also happen, although not as frequently, from ongoing mutations of the virus, where the changes occur such that they are more likely to infect humans.

What we’re seeing right now is not a surprise in terms of human infections. Humans also have alpha 2,3 receptor sites in the cornea of their eyes. If the virus gets there, it can infect the eye, but it doesn’t cause systemic illness. That, again, is the alpha 2,6 receptor sites in our respiratory tract. So far, we have not seen any of the H5N1 bird flu virus in this country causing influenza-like illness, which is what we worry about because that’s when humans, when they get infected, can spread the virus that way. That’s how you get that dynamic person-to-person transmission and potentially a new pandemic.

What we’ve seen with H5N1 has a 28-year history. It first emerged in wild aquatic birds in 1996 in Asia, and in 1997 caused an epidemic in the markets of the Guangdong Province in South China and in Hong Kong. At that time, the markets of Hong Kong were cleaned out, as were most of the farms in the Guangdong Province area that supplied Hong Kong. And it appeared that somehow the virus was gone. Well, it wasn’t. In 2003, it came back, and infected a number of individuals in Southeast Asia, including Indonesia, Malaysia, Thailand and Vietnam. At that time, we saw 110, 120 cases a year with about a 35-to-50% case fatality rate. But the key factor was that humans had to have contact with the wild aquatic birds or domestic birds. I can remember distinctly sitting on the front porch of a house in Thailand, where a young child had just died because she slept in the same outdoor area as the fighting cocks, which had recently become ill from H5N1.

Then between 2006 and 2007, it virtually disappeared. There were fewer and fewer cases, and lower case fatality rates. That is until 2016, when we saw a big increase in cases in the wild Nile River valley in Egypt among duck farmers. There were about 145 cases, and over 50% of those infected died. We thought, oh, here it goes again, and then it virtually disappeared. In fact, since 2017 there have been the fewest number of human cases associated with H5N1 since the virus was first documented.  However, in the last two-and-a-half to three years, a new clade [subset] of the virus, “H5N1 clade 2.3.4.4.b,” has taken over, and this one now causes systemic illness in a number of mammals and birds. The systemic symptoms include neurologic disease and organ damage. And that’s why we’ve seen the big case fatality rates. Now along comes infection in bovine, which we’ve never seen as part of the influenza A picture [H5N1 is a subtype of the influenza A virus], and it appears that clearly it’s associated with their mammary gland.

What I mentioned earlier about reassortment and pigs in Mexico: It is notable that pigs as a species are uniquely qualified to serve as mixing vessels for influenza, because they have receptor sites for both alpha 2,3 and alpha 2,6 in their lungs, in their respiratory tract. And so that’s where we often think of a reassortment coming from. Well, it turns out that we have now discovered that the mammary gland in bovine, the udder, actually has receptor sites for both alpha 2,3 and alpha 2,6. It is still unknown what this is going to mean long-term and what we may see when seasonal flu comes back in the fall. If workers are infected with regular flu, and H5N1 is still occurring in bovine species, could the viruses get together in a bovine udder? We don’t know.

Michael Osterholm speaking at a Fortune Brainstorm Health panel, “Stopping Global Pandemics Before They Start” in November 2016. (Stuart Isett, Fortune Brainstorm Health via Flickr)

In terms of human illness now, we have two cases documented that both involve conjunctivitis. This isn’t surprising. I think we’ll have more. But this does not pose a serious risk to human health overall. Because, again, these are the alpha 2,3 receptor sites in the eye, not the alpha 2,6 receptor sites in the lungs. Both cases were also sampled in their throats, and they found no virus there at all. Again, there’s no evidence that that virus took off there. So, the bottom line message is that this virus, in bovine is likely spread to a very real degree in the milking process.

A cow has four different compartments in the udder, each of them independent milk producers. We have seen infection in one, two, three and all four of those compartments, which really corresponds to contamination on the milking equipment that they’re using, the rubber cups that are inserted under the teats. We have no evidence right now of airborne transmission from these cattle. I’m sure there are more cases out there than we know about with regard to conjunctivitis. I don’t think that’s true with more severe respiratory illness. If we had a cluster of cases there among workers, we’re much more likely to pick them up.

We’re in totally uncharted territory. I still agree with the WHO [World Health Organization] and the CDC [Centers for Disease Control and Prevention] that the overall risk is low for humans right now. That would only change if the virus took a dramatic change and became capable of infecting humans by being able to utilize that alpha 2,6 receptor site. We haven’t seen that happen yet since the beginning of H5N1 around the world. And hopefully we won’t continue to see it, either.

Is there a concern that the avian flu could get into the pig population?

There absolutely is. Now, the good news is, studies that have looked at H5 and its potential to infect swine, haven’t really demonstrated that they’re highly vulnerable. In studies that have been done, it’s been very difficult to transmit H5 in swine. Could that change tomorrow? Sure could.

That’s one of the things that’s an underlying message here, is that everything I tell you is current as of today [May 23]. And when I say today, I mean at this hour. Come talk to me three hours from now and God knows what we’re going to know. And so that’s one of the challenges we have is that things move so quickly right now. This is where we need a great deal of humility in how we talk to the public, how we talk to farmers, to say: This is what we know and this is what we don’t know. This is what we’re trying to learn. This is how we’re going to learn it. We need to have a real dose of humility in what we’re doing.

What about beef cattle on the range? Is possible that they might become infected?

This is a major question we don’t have an answer for. There’s been very limited testing done on beef cattle. Remember, the way that the cases in dairy cattle were picked up was because of a reduction in milk production, which is something you wouldn’t have with beef cattle. So from that perspective, we’re sort of learning about what that means. I’m not sure, if that is a function of an absence of evidence or evidence of absence. At this point, we don’t know.

Avian influenzas may have been around for a long time, but something that is new is the industrial scale of agriculture that we have nowadays. Do you see that as posing certain challenges in the development of this disease or the responses to it?

Well, I think it’s an easy target. If you look at the movement of this virus, it is clearly among largely migratory birds. You look at the major impact on animal species, so far it has been on wild animals, not domesticated animals. Outside of the poultry production side, I’d have to say we haven’t really seen domesticated animal production playing a big role. And that’s why the migratory seasons have become very important for us. During this most recent spring migratory season, we saw so much H5N1 spreading in mammals, literally like butter on a knife spread across the country.

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What should the role of government agencies like the CDC be in response?

Well, first of all, we have to understand that in the United States, we have what’s called states’ rights issues. In the Constitution, there are a number of roles and responsibilities of the federal government that are laid out clearly. If they’re not laid out there, then they fall back to the states. Public health is not one of them. So historically, as much as people think about a national public health response agency, really, they’ve always been at the beck and call of states. States can decide whether CDC comes into their state and works on things.

Now, as somebody who spent, 25 years of my life at a state public health agency as a state epidemiologist, I can tell you that in Minnesota we had a very good relationship with CDC. Sometimes we needed them. Most times we did not. So, at this point, CDC really is trying to provide national leadership on things like testing, recommendations, development and communication across the states to help them understand what’s happening.

But on the ground activity is still largely done by the states. The CDC can be invited in. They have not yet, in most states, been invited in, not because the states haven’t invited them—the farmers haven’t invited them in. Even the state health agencies are not able to go on these farms. This has been a real problem, and it’s one that I think we need to take a very careful look at, because the farmer has every right to be concerned about their loss of milk production, etc., and the potential that their farm may be labeled as a flu farm.  

I have a primary concern about human health, and we need to be following closely what’s going on in these farms to see if something does happen to this virus. Does it change? If it changes, how is it changing? What does it mean in terms of human infection? Are the viruses more likely now to be able to infect humans if they’re changing? We need to get access for testing, and that has been a real challenge.

What’s the solution then for getting that access while also respecting farmers?

I think we’re starting to see some response relative to tracking the transmission on farms through the U.S. Department of Agriculture’s [USDA] program for reimbursement. Note that if you look at the challenges we’ve had with avian influenza in poultry production—turkeys, chickens, etc.—we have had incredibly good collaboration there, but that’s for a very specific reason. USDA has a reimbursement program set up for farmers that lose animals due to influenza and specifically, in the poultry world, if you start to see deaths in your birds, you want to know immediately is that is influenza because this will wipe through your operations very quickly.

The USDA will actually reimburse you for putting down birds that are not yet dead if, in fact, there is influenza in that barn. A farmer has every reason to quickly know, do I have H5N1 or any of the other influenza viruses in my flock? Well, we don’t have that yet officially for bovine and swine. USDA is moving in that direction. We are expected within 30 to 60 days, to have some kind of reimbursement program in place that would incentivize farmers to allow for testing.

What do you think the public health community has learned from the response to the Covid-19 pandemic? And how does the experience with Covid shape the current response to the avian flu?

Well, this is a topic that’s very near and dear to my heart. I’m just finishing writing another book. This one is called the Big One. It’s all about the lessons that should have, and could have, been learned from Covid to prepare us for pandemics of the future. And I’m afraid we have not done a good job learning those lessons.

There are a group of us that have lobbied hard to have a 9/11-like commission empowered, not to point fingers, not to blame, but to say: What should have and could have been learned from the pandemic that would better prepare us for future? And we have not done that.

One of the real casualties in the pandemic situation was the issue of trust.

Public health relies a lot on collaboration and cooperation. You can’t make people do some things, you know? The real challenge is convincing them to do some things for their own self-interest or for the good of their loved ones or neighbors. Right now, I think overall trust in public health authorities is at an all-time low in my 50-year career. And this is a real challenge. Thousands and thousands of Americans died from Covid that would not have had to if they’d been vaccinated. By itself it is enough to make any future response to a pandemic much more complicated than it even was four years ago.

Speaking of trust, it seems like the media shares some responsibility as well. Especially today in terms of the public’s perception and their sense of trust in the various media sources they turn to. What is the role of the media as it intersects with public health?

That’s a critical point because as we talk about the issue of trust in public health, how does that happen? Well, a large part of communication comes through the media. The media had no real clue how to deal with the Covid pandemic, initially. Unfortunately, that carried through much of the pandemic.

On January 20, 2020, I posted a note on our website saying the pandemic is here. We need to move and take action. But the WHO didn’t declare a global pandemic for almost another two months.

In March of 2020, I wrote an op-ed in the Washington Post, where I said: Do not do lockdowns. This will not work. And the reason it won’t work is because we’re going to be in this for at least three or more years. No one wanted to believe it at the time. There was a mindset that this was like a hurricane or a forest fire: It may be bad for a couple of days, but we’ll get over it, we’ll move on. And that set a tone for communication. And when that didn’t happen, that added to the mystique of, “What do we really know and not know?” People in my business ended up making some, frankly, very rigid conclusions about what was going to happen, shared that with the public and look what happened.

For example. I had an opportunity to work with coronaviruses earlier in the 21st century. In 2003, I was a part-time service support for Secretary Tommy Thompson at HHS [Department of Health and Human Services]. This was post 9/11, and worked on SARS and realized the challenges with SARS. And then I became very involved with MERS [Middle East Respiratory System], serving as an advisor to the royal family of the United Arab Emirates as MERS emerged on the Arabian Peninsula. And then in 2015, I was in Seoul, Korea, at Samsung Medical Center at their invitation to help them deal with a very large outbreak of MERS that occurred from somebody who brought it back from the Middle East and transmitted in the hospital.

And what I learned in vaccine work suggested that these vaccines provided only limited long term protection. Even if you were able to get vaccinated. We had no reason to think that this wasn’t going to happen with SARS-CoV-2 [the virus that caused the Covid-19 pandemic]. By the end of 2020, when everyone was really high on the vaccine and ready to launch it, we more or less gave people the sense that, well, we have data that says this vaccine is 94-96% effective in stopping transmission. But that was data from the first two months of the trial. I urged people, to dampen your comments here and say we don’t know what it’ll be like at six months. It could be so very protective. It could be waning immunity, and, if that’s the case, you may need booster doses.

If we had done that, that would have helped us a lot, because in the summer of 2021, when we saw large outbreaks occurring among people who had been vaccinated six months before, boy, that hurt us tremendously in terms of credibility. We could have avoided that. It was all a matter of having humility and just saying, this is what we know, this is what we don’t know, and this is what we’re learning.

I saw the same thing with modeling. Modeling is something that, I think, is the bane of my existence, especially groups that do black box modeling about what’s going to happen. [A black box model generates predictions without anyone knowing the internal logic that lead to those predictions.] Well, we had no idea what was going to happen with this virus, it was all tied to the variant emergence. But I was on talk shows, TV shows, one thing after another with some of the leading “modelers” in the country who were predicting 6 to 8 months out what was going to happen. We actually tracked several of the results of these organizations that did the modeling, and they were wrong 80-to-90% of the time. But guess what? The media had them on time after time after time, because that’s who they had to do modeling. They didn’t have a good way to police themselves.

Then on top of it, so many of the media outlets, whether it be print or audio, visual TV, they would have all these different shows or different reporters that would be dealing with this issue. And the problem was they weren’t coordinated across their organization. So, we had, you know, six, seven, eight producers at one cable station that would be dealing with the issue for their show. One person for this show, one for that show. No coordination whatsoever. They should have learned how important it would be to collaborate, coordinate and bring together their resources to have credibility. And they never did that. So, I’d say we have a lot to learn about communication, and it should start, first of all, with humility. It should, second of all, be based completely on what do we know and not know.

Don’t be afraid to acknowledge you don’t know something. Just tell people what you’re going to do to try and find out.

What will you be looking at in the upcoming flu season?

It’s going to be an interesting time. We’ll have to see what the overlay of seasonal flu and H5N1 in animals with close proximity to humans is going to look like. I don’t know. It’ll be up to Mother Nature to decide. Is that gonna throw us a curveball? We just don’t know.

What can we do to be best prepared?

Well, I think first of all, I don’t have a lot of hope for the current vaccines. They have some matching capacity right now with the strains of virus, relative to the ones that we’ve stockpiled. But the problem is that the virus that’s going to ultimately infect humans is necessarily going to have to change, meaning 2.3.4.4.b isn’t going to be the same virus that we’re seeing circulating around right now. Just like the example of H1N1 in 2009 and how the pandemic strain from Mexico replaced the seasonal strain—the vaccines had no cross protection.

What we’re going to be looking at carefully right now is what are our vaccine needs. It’s possible that all the vaccines we’ve stockpiled will have little impact on the new emerging strain.

If a pandemic does begin, we’re going to have to be very quick to identify that virus, to put it into the appropriate form so it can be manufactured as a vaccine, and hope for the best. That to me right now is by far the most important aspect of pandemic preparedness for the future.

Justin Perkins

Justin Perkins is Barn Raiser Deputy Editor & Publisher and Board Clerk of Barn Raising Media Inc. He is currently finishing his Master of Divinity at the University of Chicago Divinity School. The son of a hog farmer, he grew up in Papillion, Neb., and got his start as a writer with his hometown newspaper the Papillion Times, The Daily Nebraskan, Rural America In These Times and In These Times. He has previous editorial experience at Prairie Schooner and Image.

Joel Bleifuss

Joel Bleifuss is Barn Raiser Editor & Publisher and Board President of Barn Raising Media Inc. He is a descendent of German and Scottish farmers who immigrated to the Upper Midwest in the 19th Century to become farmers in Wisconsin, Minnesota and the Dakotas. His grandmother was born in the Scottish Highlands to parents listed in the Census of Great Britain, 1881 as “farm servants” on land owned by the Duke of Fife. Joel himself was born and raised in Fulton, Mo., a small town on the edge of the Ozark Highlands. He got his start in journalism in 1983 as a feature writer and Saturday reporter/photographer for his hometown daily, the Fulton Sun. Bleifuss joined the staff of In These Times magazine in October 1986, stepping down as Editor & Publisher in April 2022, to join his fellow barn raisers in getting Barn Raiser off the ground.

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