How worried should you be about bird flu?

Jordan: You can be forgiven if you feel like you’ve already been warned about bird flu. After all, it’s been around for decades. The first time you probably heard of H5N1 was the late nineties. And then every few years after that, when a new strain would force culling of poultry or sicken people who had come in direct contact with infected animals. But something’s different this time.

Clip 1: An unusual bird flu outbreak in dairy cows has now infected a number of herds in at least five states. Both Idaho and Michigan along the Canadian border have confirmed cases. The rise has health officials here diligently tracking the spread.

Jordan: Not only is it unusual to see this virus moving among cattle, especially in large numbers, but it also appears to be spreading through their dairy products.

Clip 2: The FDA says it found particles of the bird flu virus in samples of pasteurized milk. The agency says milk is still safe to drink, but additional testing is needed to confirm.

Jordan: Right now, no virus has yet been found in Canadian milk or Canadian cows, but the Canadian Food Inspection Agency is only now beginning to test. So we’ll find out today though, just the facts. What’s different about this strain of H5N1? What are scientists looking for and how worried do you need to be really? I’m Jordan Heath-Rawlings. This is The Big Story. Dr. Scott Weese is an infectious disease veterinarian at the Ontario Vet College at the University of Guelph. Hey Scott.

Dr. Scott Weese: Hi. How are you doing?

Jordan: I’m doing well. This is an ongoing series now on The Big Story of viruses I wish I didn’t have to talk about.

Dr. Scott Weese: Yeah, that’s our life these days, isn’t it?

Jordan: Yeah. Well start by telling us from a vet’s perspective, what is bird flu? And I guess in particular, what is the current strain that we are dealing with?

Dr. Scott Weese: Well, bird flu is just a pretty broad term for any influenza virus that infects birds and birds are the natural reservoir for this virus. There are all kinds of different types of influenza. We talk about H1N1, H5N1. Those are all different combinations of bits of the virus and all those different combinations are out there in wild birds. And occasionally we get strains that are more concerning and they can spill over into domestic poultry and cause a lot of disease or spill over into other animals, including people. So what we’re dealing with now though is a strain of H5N1 that’s unprecedented in how it’s been moving in wild birds internationally. Often we see it, it moves into poultry or you get the odd infection in people and it’s this sporadic thing. And what we’ve seen the last couple of years now, this strain has been circulating continually in large numbers in multiple countries moving between continents. And it’s just not something that we’ve seen before. And because we’ve got massive numbers of birds flying this all over the place, we’ve got a lot of chance of exposure of other animals, and that’s when we start getting more concerned.

Jordan: How dangerous is this strain? I guess firstly to domestic animals, but mostly to humans who may get it.

Dr. Scott Weese: We call this a high pathogen avian influenza, and that refers to what it does in poultry. It doesn’t mean anything for us, but this strain when it gets into things like chickens, it will kill them very quickly, large numbers of them. Other species is a bit variable. That again, other unprecedented thing about the strain is the number of different species it spilled over into. And we’ve seen infections in a range of wildlife ranging from things you’d expect like foxes, cats that will kill any birds if they’re infected. That’s a great way to exposure. But even large numbers of infections and deaths in species like seals, which aren’t something we would typically think about, but live in close contact with birds. So if you are a cat, we’ve seen a lot of serious infections, foxes, we’ve seen serious infections. We don’t really understand the milder infections very well, especially in wildlife because if you’ve got a group of foxes and they die, you’re more likely to identify, okay, that’s weird. Someone’s got to test them. If you’ve got a species that’s just feeling like crap for a couple days, right? Flu like disease, so you’ve got a wild animal that feels a little bit rough for a couple days, we’re unlikely to see that and we’re unlikely to test that. So we don’t really know how often we get run of the mill flu-like disease versus does this usually cause a nasty fatal infection when it does spill over? But we have seen those nasty fatal infections in cats, for example, the domestic species and a small number of dogs. In people, it’s not been that bad so far. Historically, if we look at H5N1 strains that have been typical in Asia, the mortality rates in people have been really high in the 30 to 50% range, realizing they’re probably milder infections that we miss, but an uptake means it can cause serious disease. Here we don’t seem to see as much with this strain, but again, it’s pretty early. And at this point I think we can say this strain doesn’t seem to have the potential to infect people as readily or cause severe disease as readily. So in a lot of ways we’re not as concerned about this strain. We’re worried about what this strain could become given time and some opportunity to change.

Jordan: H5N1 itself I gather, has been around for decades since we first detected it. What has changed recently? Is it just this strain and do we know when that happened?

Dr. Scott Weese: Well, I don’t think we really know the why, the component of why this has become such a thing in birds. Food viruses change all the time. They mutate a little bit and that can make them more or less able to be transmitted between birds and other species. It’s just a normal event with viruses that circulate. And for some reason the strain really took off. And sometimes we see changes based on the character of the virus. Something’s happened there. Sometimes we’ve just seen changes based on circumstance. It happened to get into a group that really spread it really effectively. And I don’t think we really know why this has become such a big deal internationally in birds. But there are certain things that we look for in these virus strains that will tell us whether there’s a greater ability to infect mammals and a greater ability to infect our respiratory tract. And that’s one of the things we’re worried about is we want to see strains or we’re looking for strains that are able to infect our respiratory tract because that means we might be able to spew this virus out a lot more effectively. So we’re looking for things that create a greater chance for the virus to spread between people and to cause serious disease between people. Why this strain has done what it’s done versus the older H5N1 that typically cause these really sporadic cases. I don’t think we know yet.

Jordan: You mentioned it’s been found in a ton of different animals, which is one of the unique things about it. I think the headlines a lot of people have seen recently have been referring to cattle. Where has it spread among cattle? And I’ve also seen reports of it appearing in milk and dairy products. What do we know about that?

Dr. Scott Weese: Well, this is in the US right now. We don’t have evidence in Canada, but we don’t really know if it’s in Canada yet. And it’s one of these absence of evidence versus evidence of abscess. We’re in more of absence of evidence stage at this point, right? So in the US about a month or so ago, start reports of influenza and cattle, which was surprising because cattle aren’t really a species. We think about when it comes to flu. We think about things like poultry. Obviously pigs, pigs have their own flu viruses. Pigs are susceptible to our flu viruses and other flu viruses. So they’re a species we pay a lot of attention to. Cattle really have been a non-entity historically when it comes to different types of flu strains. And the reports came out of the US saying, okay, cattle were infected and it was causing disease, but mild disease, making them feel a little bit off. Their milk production would drop, their appetites would drop, the milk would look abnormal and they would get over it. And also a human infection associated with that. So that was unique and then was found in other farms and which raises the question, okay, what’s going on? Ultimately, this originated in a bird. That’s the logical thing, but is it being spread cow to cow? Is it being spread cow to other animals? So people, domestic animals or back into birds that can spread it more and how far has it gone? Those are a lot of the questions that we’ve had and we really haven’t answered all that really effectively yet. But what it looks like now is this virus probably jumped into cattle maybe at the end of last year or December or so and came from a bird and it changed in that bird or in that jumped to cattle to a strain. It’s just a little bit different and for some reason more able to infect cattle. And what’s kind of weird about cattle is they don’t seem to be shedding much of the virus at all in their respiratory tract, which is our typical thing we think about with flu. But they shed a ton of it in milk, and this is probably how it’s spreading on farms. You have lactating dairy cattle, the cattle that are milking, it’s easy to have cross contamination when they’re being milked. So they hook up a milking machine to one cow and then they clean the next cows out or before they go there. But there’s always a chance of milk being spread down the line, and that’s probably how it’s been spread within farms. And then movement of cattle is suspected to have been the source of how it’s moved across the US. Now, is it in Canada? We don’t really know at this point.

Jordan: Should we be concerned about the fact that it has been found in dairy products and what do we know about the potential for harm to humans from consuming those things?

Dr. Scott Weese: Yeah, I think the food side really isn’t the concern here. It gets all the attention. It sure does for good reason, but I’m more worried about this being in cattle than I’m worried about being things that come from cattle and that we get exposed to. So the good thing is influenza viruses are pretty wimpy. They don’t survive very well outside of the host and cooking and pasteurization will kill them. So the food safety concern is basically just for raw milk. And there are a lot of other food safety concerns. There are a lot of reasons you shouldn’t drink raw milk, a lot of infectious disease risks. This just adds on to that pile, but pasteurization will kill it, cooking will kill it. So there shouldn’t be any concerns about getting this through food.

Jordan: In the human cases that we have seen, and I know there have been few of them, are we able to trace where people are becoming infected? Because I know from the past four or five years of all these different viruses we’ve covered, the real danger comes from human to human transmission.

Dr. Scott Weese: That’s what we’re worried about in the big picture. So we get concerned when we see more transmission and more species. So the concern about cattle is spreading cattle cow just creates more opportunity for this virus to get more adept in infecting mammals. And it also is more exposure to us. So spill into us, where the virus can change more. What we really don’t want to see as a person has human influenza, one of the strains we have circulating, and then they get exposed with cow with flu and they get infected with both of those. And then that creates the opportunity for a new flu virus that maybe is human flu virus enough that it spreads really readily, but is still different enough that our immune system doesn’t recognize it very well. And that’s how you get into the new pandemic viruses. So from a human standpoint, the infections that have happened so far largely have been really well understood. So then one of the first ones was a person who got it from his ducks and he had a lot of ducks lived in the house. It’s really close contact there. Okay. The one that was associated with cows in the US was a dairy farm. There’s not a lot of information about that person. They had mild conjunctivitis. So inflammation of the eye. When you’re working with cattle, you’re working with milk, there’s a great chance that milk can get aerosolized or splashed and it would make sense that the eye would be a place for that. So at this point, when we’re seeing human infections, these are typically people that have been involved in really close contact with poultry or people that are involved in culling poultry on flocks that are infected or this case in the dairy farm, it’s probably linked to contact with milk. We need to see more, and this is where we need more surveillance on how much infection do we get when you’ve got an exposed or an infected group. And that’s something that we’re really lacking at this point, but it does seem that it’s not spread very widely or very easily, which is what we’d expect based on the nature of this virus not really having a lot of those genetic markers that we would see with a nicely transmissible strain.

Jordan: This has been around for quite some time. Do we have a vaccine for H5N1 and do we know if it works with the current strain?

Dr. Scott Weese: Well, we have flu vaccines. Flu vaccines that we get every year are targeted based on what strains we think are circulated and circulating. H5N1 has not been on the radar or something that you’re going to need to vaccinate against. So I don’t think we have a big stockpile of H5N1. The good thing about flu vaccines is we know really well how to produce them. It’s pretty straightforward. It’s just a matter of substituting this strain for different strain. So it’s not like COVID where you have to go from zero to a hundred right away figuring out how to vaccinate against this virus. What works, what doesn’t work here? We already know what works and what doesn’t work for flu vaccines, it’s just a matter of switching out the vaccines, just like would happen if we had a change in normal human strains that we need to substitute it. So that’s good news that we know how to make flu vaccines. We know how to manufacture, distribute, and everything that’s there. Concern about this virus from a vaccination standpoint is mainly that we don’t really know whether any of the existing vaccines would give us any protection. I’ve seen some suggestion, okay, maybe we’ll have a little bit of protection from some of the vaccines that we have, but I think that’s still a bit of a guess. So we do really want an H5N1 vaccine if this becomes a human to human issue. And this is always the debate of how quickly do you start ramping up production. We can say, okay, right now we want to be proactive. Let’s start making millions and millions of doses of this. We may never use it, but we’re investing money in that. Right? In some ways that makes sense. But you also might say as well, this strain, we’re worried about this strain. It’s probably not going to change tremendously if it becomes a human strain. But if we put all this time and effort and money into creating this strain, how well is that going to protect us from the strain that actually becomes the human to human strain? And the answer’s probably okay, but we don’t really know that. So it’s a guess, right? So you want to wait long enough that you’ve got a strain and it’s really closely related to the one that’s circulating, but you don’t want to wait too long that you’re playing catch up and there’s no way to predict where that sweet spot is because we have no idea if this is going to become a more human virus tomorrow or whether it’s happened already or whether it’s going to be in a year or whether it’s never going to happen. So that’s I think the challenge in some of the vaccination planning is when do you pull the trigger and put all those resources into a vaccine that you may not use or might not be the one you want to use when the tide comes around?

Jordan: All of this is fairly reassuring with regards to the danger to humans, which is obviously what most people listening to this will be worried about. But what kind of impact could this have if it continues to spread to so many different mammals? How damaging could this be to wildlife, to cattle production, to a whole bunch of things?

Dr. Scott Weese: We don’t know, it’s a lot to answer there. For cattle production, the good thing about cattle is it’s not like poultry. If it did to cows, what it does to poultry, it’d be a different story because you can’t just replace a cattle herd in a couple weeks with a bunch of new cows. It takes a long time. These are really large animals. There’s a lot of effort goes into building up your farm, but it doesn’t cause serious disease and it’s a self limiting disease, meaning you get over it just like we do with flu. So from a production standpoint, it’s probably limited in that farm gets infected, they’ve got some impact, it’s going to cost them some money. And milk cows probably aren’t going to have long-term consequences. And if it becomes a big enough deal, then we know how to make flu vaccines for different species. We can make a flu vaccine for cow. So I think from that standpoint, it’s probably not a big deal unless this virus changes and that causes more severe disease. While the animal populations are the wildcard, right? And we had concerns when pandemic flu happened in the early two thousands. We had a lot of concerns of, okay, what’s going to happen with some of these really rare primate populations? Gorillas, where the numbers are really small deaths with few animals might be substantially relevant. And where we know we can infect them, we get close to ’em and they’re close enough to us that if it can hurt us, it can probably hurt them. So that’s why we saw some same discussions with covid, right? We don’t want to see this spill over into some of these small number high-risk species. So we do have some situations where endangered species or loss of a small number or in a distinct area could be a significant problem. So we have to realize that’s maybe an issue more broadly. This isn’t something that’s going to wipe out our fox population or raccoon population, presumably. We see lots of new diseases come in, they can have an impact, but if a large percentage of ’em survive and then they’re protected, this is something that may just circulate at a low level and cause problems but not be a major conservation issue. From a overall wild animal impact standpoint, birds are still the issue because sometimes in some species, the situations can get massive kills. Thousands upon thousands of birds, when you’ve got a susceptible species that lives in really close confines like some birds do. So there are some animal health components for sure. There may be some conservation components predating all this with avian flu in the last couple of years predating the dairy situations. We’ve had concerns about some of the raptor populations in Canada because we’ve seen quite a few deaths of things like eagles that aren’t massive numbers, longer to reproduce the populations and that seem to be quite susceptible to severe disease. So there are some issues. I don’t think we know what the big picture would be as this strain continues to spread.

Jordan: This is my last question. Just taking all of this into consideration, risk to humans, risk to animal populations. What you’re seeing this virus due so far, as a veterinary infectious disease specialist, how worried are you?

Dr. Scott Weese: I don’t think we’re worried. I think we’re paying attention to it. We’ve always paid attention to flu and a new flu strain comes or it’s in a different species. We want to sort it out. We just don’t want more influenza circulating in different animal species because that creates the chance of bad things to happen. There’s an uncertainty stage right now. I wouldn’t say I’m worried. I think the odds of this becoming a pandemic human virus are probably really low. I think the cattle aspect brings in certainly a new dynamic. And if you’re a cattle farmer or a dairy farmer, it’s very relevant to you from an animal health standpoint and from your business standpoint and from a human health standpoint, from this strain right now, only people that really should be concerned are people that work with cattle and work around milk. Because if it gets into the herd, you’ve got a chance of being infected. Your general population, we’re not at risk as long as you’re not drinking raw milk. And again, the odds of this strain being that the pandemic virus changing into the pandemic virus are pretty low. This virus is still circulating in wild birds readily in lots of different areas and still jumping into mammals periodically. So dairy cattle are the devil we know right now, but there are a lot of other mammals getting infected sporadically that we just don’t know about. So maybe that’s a good news, bad news type of thing. I think that we can contain things in cattle, which is good. If we know we have this virus on a farm, we can probably prevent its spread. If we identify what’s going on in Canada, we can come up with strategies to maybe get rid of it from the population. If it’s here, this is a virus that’s potentially eradicable in cattle with good infection control measures. We can’t eradicate it in wild birds. There’s just no way to do that. We’re not vaccinating every bird and vaccination is not even going to protect from shedding anyway. Right? So from the general population standpoint, the concern is really just continuous circulation of the viruses. Could something happen? The imminent risk standpoint is people that have contact with animals that might be infected. So dairy farmers are on the radar now. People that work with wild bird rehabilitation and just general contact with birds. That’s why we say stay away from wildlife. And the question of things like bird feeders, should we be taking bird feeders down right now? And probably because bird feeders bring birds in closer proximity to us, into our cats, and bring birds in closer proximity to each other, which might create some risk for that. But for your average person, it’s something I guess to be aware of, but not something you’d be concerned about.

Jordan: Dr. Weese, thank you so much for this.

Dr. Scott Weese: Thank you.

Jordan: Dr. Scott Weese from the University of Guelph. That was The Big Story. For more, you can head to TheBigStorypodcast.ca to find all sorts of other episodes about all sorts of other viruses and how much you should worry about them. You can also give us feedback by emailing hello@TheBigStory podcast.ca or by calling us and leaving a voicemail. To do that, just dial 416-935-5935. The Big Story is in every podcast player. It’s on the website that I just gave you, and it’s in your smart speaker if you ask it to play The Big Story podcast. Thanks for listening. I’m Jordan Heath-Rawlings. We’ll talk tomorrow.