Avian flu has been spreading across the United States since 2022, with several cases even being detected in humans, including 10 in Colorado.
Now, federal health officials are reporting that a Nevada dairy worker has tested positive for a variant of the virus that hadn’t yet been identified in cattle.
The Colorado Department of Agriculture is asking people to report sick domestic birds that have died from unknown causes to the Colorado State Veterinarian’s office using a reporting form available on the department’s website. People are also being asked to send dead birds to Colorado State University’s diagnostic laboratory.
People can also contact their local Colorado Parks and Wildlife office with reports of dead wild birds.
Utah’s Department of Agriculture and Food is asking the public to report domestic birds with symptoms of bird flu to the State Veterinarian’s office. Anyone who finds groups of five or more dead wild birds should contact their local Division of Wildlife Resources office.
Wyoming is asking residents to report instances of illness and unexplained death of domestic birds to the Wyoming Livestock Board. People can report dead wild birds to the Fish and Game Department, with a reporting form available online.
Rocky Mountain Community Radio’s Caroline Llanes spoke with Cornell University’s Amandine Gamble, an assistant professor who focuses on infectious diseases, wildlife, and ecology, to learn more about the virus.
Editor’s note: This interview has been edited for length and clarity.
Llanes: So what can you tell me about this current avian flu outbreak that we're seeing now? Is this different from what we were seeing in 2024?
Gamble: The outbreak we are experiencing now in the U.S. and in the rest of the world has been actually kind of the same old variant that has been lasting for a few years, that started circulating in the 90s in Asia, and that has just been slowly spreading through the world. But since about 2022 — so it really started in late 2021 and blew up in 2022 — the virus suddenly started spreading very quickly and, especially in wildlife. So we've always had, you know, outbreaks in poultry farms here and there in Asia and in Europe. It's the virus itself that seems to have evolved to become more transmissible. So what we think usually happens is that a highly pathogenic variant of the virus evolved in poultry farms but then can spillover to wildlife, and when they're in wildlife, they can mix with a low pathogenic avian influenza virus and they can acquire some of their genes, and then they become a mix of the two viruses and they can acquire new traits. So, for instance, on top of being highly pathogenic, they also become more transmissible, which we think is what happened with the strain we have now.
Llanes: How is this kind of little mini outbreak that we're seeing now different to what we might have seen from this virus in the past?
Gamble: One important thing we noticed with that specific branch of the family tree of avian influenza viruses is that we've detected it in way more species than we had before. In the past, it was poultry farms, and we would have geese and ducks around poultry farms. And every now and then, rarely maybe a gull or another bird, but that was it. We didn't really have big outbreaks in wildlife. In 2022, we detected huge outbreaks in seabirds in Scotland. But we also had the virus reaching Antarctica, and we had outbreaks in penguins, and that's the same virus. We say 'now we can travel so fast, the world is so connected.' It's true for viruses. So it reaches really remote places.
And so, besides more birds, also we had more mammalian species infected than we've ever had with any influenza virus. And so, for instance, in North America, we hear a lot about dairy cows at the moment, but also in wildlife, we had raccoons and foxes. There was a polar bear at some point, there are walruses, lots of mammals that are also being infected. If mammals are infected so easily and can die from infection, even though, you know, it's originally a bird virus, does it mean that we humans, as much as we also are at higher risk than we were in the past?
I don't know what is the egg from the chicken. I don't know if we have more host species now because it's spreading so fast that it's reaching new areas or if it's spreading so fast because it's infecting so many host species that it has more opportunity to spread. But it's like the intensity is bigger than what we've ever experienced. And the diversity of species that are being affected is wider than what we've ever seen. And both are probably related. But I think that's the main feature of this virus.
Llanes: Let's talk a little bit about the impacts of climate change. Does a warming climate impact how these outbreaks occur and spread?
Gamble: It's the annoying answer, but it depends. I think the system where it's the best studied is with vector-borne diseases like mosquito-borne disease and tick-borne diseases because we have a clear understanding of, as the planet is getting warmer, we are getting more and more places that become suitable for the mosquitos, all the ticks to live. Like places where it used to be too cold to live, now it's good enough for them to spend winter, for instance. So we think that explains why we have the expansion of some viruses like West Nile virus or we have Lyme disease in ticks, like those pathogens, we think there is that relationship with climate.
For other pathogens, I think it's a bit harder to say. Sometimes when people say “climate change,” what they really mean is anthropogenic changes, so like human-induced changes. And for that, there is a clear link with a lot of diseases. Because for instance, I was telling you how avian influenza, we think that it evolved from poultry farming. And, you know, that's a human activity, we think, leading to the emergence of a disease that wouldn't exist if we didn't have that specific activity.
So I think if we extend from not just climate change, but anthropogenic changes, that then there is like, yes, for sure there is more, and there is going to be more because also we have more contacts with wildlife because we are fragmenting their habitats, because we're destroying a bit of forest here and a bit of wetland here and there for urbanization, and agriculture. We're making the interface between wildlife and humans longer. And so we have more opportunities for pathogen exchange. There is also the whole discussion about how because we are degrading the habitat of wildlife, then wildlife might be in poorer health states. And if they have less resources to sustain themselves, then one of the first things they would sacrifice is immunity, because you know that we still need to be able to breed and find shelter and so on. But then they might invest a little bit of their resources in fighting infectious disease, so they might shed more infectious disease. So everything interacting together, it’s very hard to make a clear relationship, but we definitely see some evidence for some diseases.
Llanes: What are researchers going to be looking for as we continue to get more information and data about these outbreaks?
Gamble: I'm on the wildlife research side, so I think that for wildlife, like a big thing is, as we speak, most of the wildlife surveillance has been very passive and opportunistic. Every now and then, someone will bring a dead animal to a wildlife rehab center or a sick animal to a wildlife center and be like, ‘It has the flu.’ But there's been very little like systematic screening. So it means we have a very poor understanding of, for instance, what is the actual extent of the outbreak in wildlife because it's, you know, first, we're missing a lot of dead cases. Even if we were collecting all the dead animals, we would still miss a lot because of being scavenged by something else or they'll actually be too deep in the grass.
But also, there are probably a lot of infections, you know, like for humans, where we have infections that are not lethal, and we need to know about those because there are some individuals that could potentially play a role in spreading the virus. If they're infected but they're not sick, they can move around and contribute to moving the virus around. So yeah, more active surveillance. Obviously, there are a lot of things happening in the lab, like trying to understand why the symptoms are so different between different animals. I think that there's going to be more transmission between wildlife and domestic animals. Looping back to my (point), we need more systematic surveillance on both sides.
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