Bird flu has also infected cattle, cats and some humans

[00:00:00] Host Amber Smith: Upstate Medical University in Syracuse, New York invites you to be "The Informed Patient" with the podcast that features experts from Central New York's only academic medical center. I'm your host, Amber Smith. We've heard about bird flu in the news lately, so I'm checking in with Upstate's chief of infectious disease for what's important to know about this virus. Dr. Elizabeth Asiago-Reddy is also an associate professor of medicine at Upstate. Welcome back to "The Informed Patient," Dr. Asiago-Reddy.

[00:00:31] Elizabeth Asiago-Reddy, MD: Great to be here, Amber. Thank you.

[00:00:34] Host Amber Smith: My overarching question is, how concerned do we need to be about bird flu?

[00:00:41] Elizabeth Asiago-Reddy, MD: I think we're in a place right now where we definitely need to be concerned, but we don't have, right now, an immediate threat to human health. So I think an appropriate level of concern is occurring in terms of investigating what's going on in animals and trying to make sure that it doesn't impact humans.

[00:01:02] Host Amber Smith: I know that we're sort of in the middle of the traditional influenza season. Are we testing people to see if it's influenza or if it might be bird flu?

[00:01:12] Elizabeth Asiago-Reddy, MD: Yes. The way things are working right now -- and to a certain extent, it depends on which type of influenza test you take -- bird it will test positive as an influenza A virus. And if you test at Upstate, for example, this will actually subtype the virus right away to let us know which influenza A virus it is.

If it is indeterminate, meaning that it's not one of the human influenza A viruses that we expect to see circulating, it will be sent to the New York State Wadsworth Laboratory for more detailed investigation. And at that point, they could determine if it was an avian influenza.

[00:01:55] Host Amber Smith: But at this point it mostly infects wild birds, or caged birds, or...?

[00:02:02] Elizabeth Asiago-Reddy, MD: It is impacting all sorts of birds at this point. So wild birds, by far and away, are the largest reservoir because we're not able to control them, and they are circulating across the globe. So they are really the reason why we have this ongoing situation with influenza on an annual basis anyway.

But the poultry and backyard flocks are being impacted by this because, of course, they come into contact with wild birds.

[00:02:37] Host Amber Smith: What about other animals? I've heard of dairy cows and cats, right?

[00:02:42] Elizabeth Asiago-Reddy, MD: Yeah, so dairy cows are really the biggest one that stand out. And this is something that's new. We haven't seen this level of infection in dairy cows in the past.

What we have seen in the past, and what's more typical, has been infection in pigs. You may remember swine flu from about 10 years ago or so. Pigs, we know for a long time they have certain receptors in their lung system that make them more susceptible to influenza viruses. And we didn't expect this quite as much in dairy animals.

So we're still figuring out why is this happening? Is there something about the virus that has changed that has made it more likely to infect dairy cows? And what does this mean moving forward? But what we have seen since last spring, spring of 2024, is that there has been a multi-state outbreak of an avian type of influenza virus.

So this is an H5N1 virus -- that's our typical avian influenza virus -- in dairy cattle. And multiple herds of dairy cattle have been impacted, and especially in California, but all across the Western United States in particular.

[00:04:00] Host Amber Smith: I've heard of poultry and duck farms recently that had to euthanize all of their chickens and ducks because of bird flu. Are they having to euthanize cattle on dairy farms?

[00:04:12] Elizabeth Asiago-Reddy, MD: They typically have not had to euthanize the cattle. But there is a lot of difficult management that needs to go on because these cattle now need to be separated from others so that they're not impacting the other cattle. So, bird flu among birds tend to spread almost immediately so that all members of the flock are immediately impacted.

The, dairy cattle, there's been some cases where you can separate certain members of the herd out so the herd, the entire herd, is not necessarily impacted, but it is significantly resulting in reduced milk production, and listlessness, low energy in the dairy cattle that are impacted. So it's having very significant economic impacts on those herds.

[00:05:01] Host Amber Smith: Now what about cats? Do we know how the cats have gotten bird flu?

[00:05:06] Elizabeth Asiago-Reddy, MD: Presumably by the same mechanism, although it has not been such a widespread problem to date, and especially I think because cats are more, hey're not grouped together, so they may have sporadic interactions with birds, but we don't have herds of cats for the most part. So the potential for spread, widely among cats, is much lower.

And so when a poultry farm has to cull all of their chickens, is that effective? Are they able to stop the flu that way? It is effective, but as you can imagine, it's very significant. You lose the entire flock of animals. So, it's very problematic. And in addition to the flock itself, nearby flocks also need to be assessed. So if you have farms that are next door, or down the road, et cetera, those also need to be tested and then made sure that it hasn't impacted them as well. And so it takes, this is obviously one of the things that we're seeing in terms of egg prices and reduced availability of eggs is the fact that entire flocks have had to be culled because of this avian influenza.

[00:06:22] Host Amber Smith: This is Upstate's "The Informed Patient" podcast. I'm your host Amber Smith, and I'm talking with Upstate infectious disease chief, Dr. Elizabeth Asiago-Reddy about bird flu.

So how similar is bird flu, or different, is it from traditional influenza?

[00:06:40] Elizabeth Asiago-Reddy, MD: What is the most important that makes it different is that it, right now, even though it has a limited capacity to infect humans, it has not developed the capacity to spread from one human to another.

So that is where we end up in a pandemic, or at least an epidemic situation, is when a person can become infected with an influenza virus and pass it on to another person. So avian influenza, as it stands right now, people who have very close contact either with a dairy cattle or with birds that are sick with this virus, can become infected. But they cannot pass -- as we've seen so far, and this is where we need to monitor closely -- they cannot pass it on to another person, even in their household, et cetera. So it strictly has evolved to infect and to be passed between the animals that we're seeing it infect at this point.

Otherwise, when we're talking about symptoms, these can be highly variable. So right now, there are a small number of cases. There have been about 50 cases that have been transmitted in the last year from dairy cattle to humans. Those cases have involved actually fairly mild symptoms, more on average milder than what we see from your typical Influenza A that's circulating right now. So it's kind of flu-like symptoms, with feverish, kind of malaise, that type of thing. Actually, a number of these people have not even had fever. They've had congestion without fever, conjunctivitis, which is redness of the eyes has been a prime feature of this particular strain of virus.

Now, there is another version of the H5N1 avian influenza virus that has recently been detected in a dairy herd in Nevada. That is a slightly different version than what we were seeing all throughout last year. And that version is responsible for the deaths of individuals. There was a woman in Louisiana who had a small backyard flock and who cared for a sick bird, and she ended up passing away. She was older than 65 years old. I don't have other details about her health history. And there was also a teenager in Canada who was impacted by bird flu who became very severely ill and required intensive care, but has fully recovered.

Those two individuals both had this different strain of, H5N1 than what we've been seeing throughout the rest of the year. That has happened this year, in 2025. So we are definitely keeping our eyes on that because even though we haven't seen a demonstration that that virus can be passed from person to person, the level of symptoms was more severe than with the one that we were seeing throughout 2024.

[00:09:43] Host Amber Smith: And the seasonal flu vaccine that we got in the fall, that doesn't work against bird flu?

[00:09:50] Elizabeth Asiago-Reddy, MD: Not specifically. I mean, there may be some degree of benefit, but it's not specifically targeted against these types. And the reason for that is because, the way that the vaccines are designed is on the hemagglutinin and neuraminidase proteins. And so that's what the H and the N stand for. Those are proteins within the influenza virus that are responsible for causing a lot of what makes you sick when you get the flu.

And so vaccines are designed to target the specific combination of hemagglutinin and neuraminidase that we expect to see in human influenza from year to year. So currently the vaccines that we have are protecting against H1N1 and H3N2, as well as an Influenza B. So you can see there's some crossover there with the H5N1, but it's not a perfect match for H5N1. And you know, there would be no reason right now to do widespread vaccination of people against avian influenza because we're not seeing it in a widespread way in humans.

Because of the way these vaccines are made, the potential exists to make a vaccine relatively quickly, because we know the basic process of putting together a vaccine that involves these types of components.

[00:11:13] Host Amber Smith: Well, let me ask you, because we're heading towards spring anyway, any advice for whether it's safe to have bird feeders in your backyard?

[00:11:23] Elizabeth Asiago-Reddy, MD: So far the CDC has not recommended against bird feeders. And part of that is because bird feeders tend to attract a diverse array of birds, and they don't often actually reside in the bird feeder. So yes, they're potentially interacting with each other, but they're not actually living together. And so it doesn't seem like it's a very significant risk for, let's say, concentrating an epidemic of bird flu.

Also the general recommendation across the board is don't pick up dead birds that you see lying around, whether they were part of your own backyard flock or they were at your bird feeder, et cetera. That is a critical and pretty easy way of protecting yourself. Obviously if it's a wild bird, you're probably going to just ignore it or move it out of the way if you need to. If it's a member of a flock that you're raising. So let's say you have backyard chickens. And you, if that's the case, then you can actually Google. There are numbers where you should call to try to get assessed. So you can call your veterinarian. That's step one if you're not sure where else to call. And then from there they'll direct you toward testing and seeing whether there is actually a danger to the entire flock.

[00:12:43] Host Amber Smith: Now, what about eating eggs? Is it safe to eat eggs from grocery stores or from farmer's markets?

[00:12:50] Elizabeth Asiago-Reddy, MD: As we've seen thus far, it is safe to eat eggs, but that's why we cook eggs. OK, so, we should not be eating raw eggs across the board, period, for a number of different reasons, this being one of them. The virus is unlikely to really concentrate itself on eggs anyway. It would really have to be like a very fresh, raw egg for us to be able to get influenza virus from it because it would be expected to be on the outer surface of the egg. So eggs, no. The way that we're eating them, it's not really a concern.

Chicken, eating chickens that have been immediately slaughtered, that is really the potential risk that could occur. So people who are slaughtering their own chickens, buying chickens that are fresh slaughtered, then you want to take care to make sure you're washing all surfaces, washing your hands fully, cooking the chicken before you're eating it, and not consuming raw parts of the chicken, or particularly chicken blood.

[00:13:50] Host Amber Smith: What about raw milk?

[00:13:52] Elizabeth Asiago-Reddy, MD: I'm glad you asked that question, because this has been a source of questions back and forth. I think there was recently a pretty big publication of lay press talking about some of the potential benefits associated with drinking raw milk. But the reality is, is that raw milk is a danger in this situation. This is definitely one of the reasons why we would recommend against drinking raw milk, amongst the potential for other pathogens as well, but absolutely this can be transmitted in raw milk.

[00:14:23] Host Amber Smith: Now what about people who work on dairy or poultry farms? Are there any protective measures they should be or could be taking to protect themselves?

[00:14:33] Elizabeth Asiago-Reddy, MD: Yes, and there are a lot of details on CDC websites that are available to review how to take care of yourself depending on the situation that you're in. So certainly your boss should be explaining what are the necessary steps based on the, the situation at hand.

If there has been any identification within a flock, then people are recommended to wear specific types of personal protective equipment to keep themselves safe, or the same thing if there has been recognition within a dairy herd. So that depends on what the recognition has been, what your specific role is in terms of how you interact with the animals, and again, all of this is available through the CDC as well as several agricultural organizations, on how to protect yourself and what would be recommended.

[00:15:23] Host Amber Smith: How could this become more of a concern?

[00:15:25] Elizabeth Asiago-Reddy, MD: So the concern that exists is that now that dairy herds have been exposed to this over a long period of time, the longer that this is living in any group of animals, the more likely it is that it could mutate, right?

That's just the same way it is with any kind of virus. So if we have more and more dairy herds that are impacted, and especially if we see sort of recirculation of the virus, like one of the things that's concerning is that this new version that made those two people so sick has been detected in cows who have already been exposed to the other version. So that's nerve wracking because it allows for the possibility of recombination and creation of new viruses that have new mechanisms of transmission. So all it has to do is take a step that allows a new mechanism of transmission that would allow it to transmit from human to human, and that's where we're in big trouble.

The more time it has circulating around in any given population, the more likely it is that something like that could happen. So that's what happened with swine flu, is that for whatever reason, the right combination occurred, and it was able to not only go from pigs to humans, but now from human to human.

I agree that we have reason to be concerned based on these dairy herds and what's happening. But we just don't know. It could be any random moment. And the way you can contrast it is influenza B. So Influenza B only infects humans, and we see less illness, less change in illness for influenza B, and no real worldwide pandemics of influenza B because it's just a stable presence within the human population. It doesn't have as much opportunity to mutate as it does with an animal reservoir.

[00:17:11] Host Amber Smith: Interesting. What about, is there seasonality to bird flu? Will things change or get better in the summer, in the warmer months, or not?

[00:17:21] Elizabeth Asiago-Reddy, MD: Yes, there is seasonality, and all of the human flu that -- we think ultimately this probably all came from birds in the beginning, right? -- but, yes, there is seasonality in terms of when things are worse. But that's the other thing that's concerning about the dairy herds is that they've been perennially infected, because this hasn't really gone away since it was first identified about a year ago.

So the concern is, has this become endemic in some dairy herds, and what does that mean about the ability for it to mutate over time?

[00:17:57] Host Amber Smith: Well, this has been very informative, and I appreciate you making time for this interview, Dr. Asiago-Reddy.

[00:18:02] Elizabeth Asiago-Reddy, MD: Yes. Thank you very much.

[00:18:04] Host Amber Smith: My guest has been Dr. Elizabeth Asiago-Reddy. She's an associate professor of medicine and chief of infectious disease at Upstate. "The Informed Patient" is a podcast covering health, science and medicine, brought to you by Upstate Medical University in Syracuse, New York, and produced by Jim Howe, with sound engineering by Bill Broeckel, and graphic design by Dan Cameron. Find our archive of previous episodes at upstate.edu/informed. If you enjoyed this episode, please invite a friend to listen. You can also rate and review "The Informed Patient" podcast on Spotify, Apple podcasts, YouTube, or wherever you tune in. This is your host, Amber Smith, thanking you for listening.