Note: Transcripts may contain errors. If you wish to re-use all, or part of, a transcript, please contact CBC for permission. Please check the corresponding audio before quoting in print. Copyright © CBC 2024

The Dose Transcript for April 18, 2024

Host: Brian Goldman

BRIAN GOLDMAN: Hi, I'm Dr. Brian Goldman. Welcome to The Dose. You've probably heard about avian flu. It's a type of influenza A known as H5N1. It's called avian flu because over the past few decades, it has struck birds on farms and in the wild. But now, it's infecting cattle. H5N1 has been identified in herds of cattle across six states, including the Canadian border states, Michigan and Idaho. It's that and some other developments that have smart flu watchers concerned. So this week, we're asking, what's going on with H5N1 bird flu? Hi, Raywat. Welcome back to The Dose.

RAYWAT DEONANDAN: Thank you so much for having me back.

BRIAN GOLDMAN: As an eminent watcher of emerging infections, what makes you decide that it's time to go public with your thoughts and concerns?

RAYWAT DEONANDAN: Haha, when people ask me to. That's what it comes down to. And these days, people ask me very frequently to be public about thoughts around infectious disease, because that seems to be on a lot of people's minds these days.

BRIAN GOLDMAN: And that's why we came to you. But before we begin, can you give us a hi, my name is? Tell us what you do and where you do it. Just adlib.

RAYWAT DEONANDAN: Hi, my name is Raywat Deonandan. I'm a global health epidemiologist with the University of Ottawa.

BRIAN GOLDMAN: Let's go right to the beginning. What is H5N1 bird flu?

RAYWAT DEONANDAN: H5N1 is a strain of influenza. And it's not the typical seasonal flu that we're all used to, that most of us line up at the drugstores to get our seasonal flu vaccine for. It's a different beast entirely, and we've known about it since the 60s. I think it was first detected in Scotland. But since the late 90s, it's been known to occasionally infect people. And when it does, it can be quite lethal. So it's a serious concern. It exists mostly in the bird population, hence avian flu. Occasionally, it jumps to mammals, as it's been doing lately. And occasionally, it jumps from mammals and from birds into people. That's when it gets scary. What we're really concerned about is will it move from people to people in a sustained way?

BRIAN GOLDMAN: How is it related to human flu?

RAYWAT DEONANDAN: I'm not a Geneticist or a virologist, but there are obviously some genetic differences that make it distinct. It lives primarily in birds, hence the name avian flu. It's adapted to exist in birds. But occasionally, it can develop a mutation that allows it to jump into mammals, and perhaps from mammal to mammal. What we're concerned about is it will share DNA with a flu that is adapted to live in humans and learn how to live in humans, in which case it will move from person to person with presumably the same alacrity with which the seasonal flu moves from human to human. And that's troubling because it is sufficiently different that it's more lethal.

BRIAN GOLDMAN: In the current outbreak involving cattle in the United States, at least one human being has been infected, as reported by the Centre for Disease Control in the United States. Do we know how that happened?

RAYWAT DEONANDAN: The assumption is that that person got it from contact with dairy cows. It's unclear if that's true or not, but it's probably true. In fact, pretty much every known case of avian flu infecting human being since 2000 or so has been the result of a human being in contact with some kind of animal. There's some suspicion that maybe a handful of cases were when a human being got it from another human being. That's a rarity. But in this case, it seems pretty clear that it was an agricultural worker who got it from being in close proximity with a dairy cow.

BRIAN GOLDMAN: Over the years, there have been, what, 800 cases in which human beings have been infected with H5N1, something like that, a little more than that?

RAYWAT DEONANDAN: Yeah, like 860 or 80 or so. The exact number escapes me at the moment, but those are the known cases. And of those known cases, more than half have died. That's the scary part. We call that the case fatality rate, the fraction of known cases that die. So we're looking at somewhere between 50 and 60%, which is terrifying. However, it's important to keep in mind that there are likely instances of people getting it and not even knowing about it because their symptoms were so poor, in which case the actual fatality rate will drop considerably. How much? Well, that is unclear. And some modelling suggests that the true fatality rate for H5N1 in humans is probably around 14 to 30%, which is also pretty terrifying. That's extremely high for an infectious disease. So it's not probably as deadly as the current data suggests, but it probably will be significantly deadly if it moves into a truly human modality.

BRIAN GOLDMAN: 14 to 30% case fatality rate would put it higher than most of the diseases for which we have vaccines like measles, chickenpox, whooping cough, tuberculosis. Would it be more than tuberculosis?

RAYWAT DEONANDAN: Yeah, I think so. But it's important to keep in mind that even though it's more fatal than those diseases, it's not more contagious. I think as a result of COVID, everybody knows what the reproduction number is now. Reproduction number is the average number of cases that an infected person will create before their infection has resolved, and you can be resolved either through getting cured or through dying. And so before you’re resolved, how many people on average will you infect? For measles, it's thought to be between 12 and 18, you know, which is very, very high. For COVID, currently maybe six, seven, eight. For flu, it tends to be around, you know, two or three. So it's not nearly as contagious so far. But if you do manage to get it, you have a higher chance of dying. And keep in mind, we've known about this disease for at least 20 years. We've been studying it closely for at least 20 years. It's not something new like COVID was, and we have vaccines. That's the good news, right? So we have an effective commercially available poultry vaccine that is being used in many countries already to create a buffer zone around domesticated poultry in the case of the disease running wild in those populations. But the FDA has approved a couple of formulations for use in humans as well, so it wouldn't need the rediscovery of a new vaccine technology in order to ramp up production. All we gotta do is press the production button and produce a whole bunch of these vaccines right now. Keep in mind, though, that the data around the human H5N1 vaccines is based on how well it produces antibodies. We don't know exactly if that will translate to actual immunity. Probably will, though.

BRIAN GOLDMAN: You know, we talked about the idea, the notion that one dairy worker or someone who was in close proximity to a dairy farm might have been affected directly. But how is H5N1 currently spreading right now? What do we know about that?

RAYWAT DEONANDAN: It seems like the cows are getting it from contaminated milking equipment, which is interesting, right? So touching common surfaces. We call that fomite transmission. Like an example of fomite transmission would be if I've got a cold, I cough in my hand, I touch a doorknob, somebody else comes along, touches the same doorknob and touches their face and become infected. So I have infected that person via the fomite, and the fomite in this case would be a doorknob. So it looks like there’s fomite transmission via contaminated milking equipment. You can get infected by eating an infected animal, and that seems to be how a lot of wild animals are getting it. And in fact, we've detected H5N1 in polar bears, sea lions, penguins, foxes. You know, the presumption there is they’re getting it from eating dead birds. And you can get it from being coughed on in the face. You have direct transmission of some kind. So droplets. There's probably an airborne component to it. That's unclear, but there probably is. So there's a whole variety of ways that one could acquire it and that the cows are likely acquiring it.

BRIAN GOLDMAN: It sounds like that would be a kind of an occasional occurrence. The nightmare scenario, as you've laid out, as others have laid out, is that H5N1 acquires the ability to go from human to human. What would be the process for that?

RAYWAT DEONANDAN: The textbook process for that would be if it infects somebody who's already infected with a similar virus, like a flu virus, that is adapted to human presence. Then viruses have this nasty habit of swapping DNA. Say, hey, I've got this little chunk of genetic material that allows me to do this. Do you want it? And H5N1 says, yes, I want that, and it learns then how to infect other people. So Michael Osterholm, a famous flu scientist, has suggested that he's not as concerned about this disease infecting cows and birds as he would be if it were to infect pigs, because pigs tend to be the home of more influenza strains that we share with them. So imagine this gets into a pig that is infected with a human influenza. Suddenly, it learns how to infect us very, very quickly. That is a nightmare scenario. Or it ends up in a person who's also infected with, you know, seasonal flu and learns how to infect the rest of us, which is why it's always a good idea to avoid being infected with a number of viruses, including seasonal flu.

BRIAN GOLDMAN: How much protection would we have from the vaccines that are available right now for H5N1?

RAYWAT DEONANDAN: It really is unknown. The poultry vaccine appears to be a very high efficacy. Seasonal flu vaccine gives us between 40 and 60% on a good year of protection against symptomatic disease. Sometimes, it's very, very low because it's not well-matched to the circulating strain. The good news right now is that the genetic testing of the H5N1 strain that's infecting the cows in the USA is extremely close to that that was used to produce the human H5N1 vaccines that are currently stockpiled. That means it's going to be a good match. But we don't know what the actual efficacy is going to be because the only testing that's been done is on how much antibodies are produced when a person is given that injection. So we don't know how it actually works in real life, but there's every expectation that it should work fairly well.

BRIAN GOLDMAN: Hopefully, we won't ever have person to person spread of H5N1, but the fact is we already have a vaccine. We're not trying to play catch up to develop a vaccine after the horse has left the stable, as it were.

RAYWAT DEONANDAN: That's exactly right. And it's an old technology vaccine. So that should quell some of the concerns people have over mRNA technology, for example. But as an aside, it is possible to make an mRNA vaccine for this also. And that would be an advantage because you could produce it much more quickly.

BRIAN GOLDMAN: So we've talked about the potential of this vaccine to be efficacious. How available is it? Who's got it?

RAYWAT DEONANDAN: It's not commercially available. So the poultry one is. So farms could buy that one right now for the poultry. The human one has been licensed in the sense that you could use it on humans, but you can't buy it. As a result, the FDA has stockpiled a certain number for emergencies, and I don't know if Canada has stockpiled any or even if Canada has licensed them. I wouldn't be surprised if we had. So one of the challenges here is in the event of an epidemic, how quickly can we manufacture these things? And that is a concern because it's an older technology. They have to be incubators and eggs, you know, things like that. So it could take a long time, which is why I think it's probably a good idea to look into mRNA production.

BRIAN GOLDMAN: What about antiviral treatments?

RAYWAT DEONANDAN: Success using monoclonal antibodies treating flu has been limited. Not nearly the game changer as one would have hoped. But we do have antivirals like Tamiflu, and that seems to be quite effective. In fact, the one person in the USA that has been infected with H5N1 in this current outbreak has been treated with Tamiflu and is doing quite well. So that is effective. But again, do we have a lot of Tamiflu on hand in case this was suddenly affect tens of thousands of people? I don't think we do. The rate limiting step is availability of these resources.

BRIAN GOLDMAN: What are some of the ways that industry is responding to bird flu outbreaks?

RAYWAT DEONANDAN: We have a history of the last few years of culling large numbers of farm animals and wild animals. Tens of millions of both wild birds and farm birds have been killed when the presence of H5N1 is detected. And that sounds cruel, but it's necessary. That's done all around the world. So a silent army of invisible public health workers is keeping us safe by doing that dirty work. As I mentioned, some countries are mass inoculating their farm poultry populations to prevent deeper spread. I don't know if anyone's looked into inoculating the herd animals yet. I don't think that's a possibility because there are some, to my knowledge, a vaccine that's been approved for that population. But it doesn't seem to be hurting the cows, the H5N1, that is. It seems to be affecting their milk and therefore challenging onward spread of the disease, but doesn't seem to be lethal towards cows. And of course, there's monitoring. There's surveillance of the herds and surveillance of the farm workers, which to my mind, is more important. If we can keep our eye on the people in close proximity with those who are in close proximity with potentially infected animals, then we can swoop in and inoculate strategically and prevent onward spread.

BRIAN GOLDMAN: What about our eating habits? Should we avoid beef, milk or eggs because of what we've been hearing, for instance, about outbreaks in cattle?

RAYWAT DEONANDAN: Well, I'm a vegetarian, so you're asking me to contribute to the propaganda that I really want to spout out at you. But no, I don't think there is sufficient reason based on this alone to curtail eating habits. I think it's probably sufficient to just follow general hygiene practices like cooking your meat. Don't eat raw meat. Making sure your milk is pasteurized. Don't eat, don't drink raw milk. Like keeping your raw meat and eggs separate from the rest of your food when you buy it, in the fridge and things like that to prevent cross-contamination. I think if we follow those guidelines, we’re probably free from acquiring this disease via the food chain.

BRIAN GOLDMAN: And finally, I wanted to speak to you on this episode of The Dose because you wrote a blog and you expressed concern. And I know on social media, you've said that you're concerned. You're watching H5N1. What are you hoping to accomplish by talking to us on The Dose and by writing your blog, which was intended for the public?

RAYWAT DEONANDAN: Yeah, a few things. One is to curtail the panic, because those laypeople who are watching are probably scared because they hear about the scary case fatality rate. Second is to understand why professional public health scientists are watching this, because we are aware this could be a scary pandemic if it becomes one. Third is to prepare people in case it does acquire human to human sustained transmission, to prepare us to step up and do the right thing, which will be to accept vaccination when it becomes available. And lastly, to recognize that this is not an apocalyptic scenario necessarily. There are some advantages we have here. So the good news is that so far, there is no evidence of sustained human to human transmission. Second is that it's not as contagious as something like COVID. Third is it's not new. We've known about this for decades. Fourth is we have a vaccine. All we got to do is step up its production. Next is we have a treatment, Tamiflu. So there's a lot of good news here. The bad news, of course, is that it might make the leap into sustained human to human transmission, in which case we're looking at another public health emergency. So I want people to be aware of the good news and the bad news, and the fact that there are public health measures that can be taken to curtail the bad news if people participate and cooperate. So I want greater cooperation from the population. COVID has shown us that there is deep distrust of the so-called experts, deep distrust of authority. Some of that has been exacerbated by some people in the political corners. But I think by getting ahead of the narrative, laying out the facts as we know them, maybe we can buy some more trust.

BRIAN GOLDMAN: As a physician and somebody who's been a flu watcher myself for many, many years, I hope that you're right. Raywat Deonandan, thank you so much for speaking with us.

RAYWAT DEONANDAN: It's my pleasure. Thank you so much.

BRIAN GOLDMAN: Raywat Deonandan is a global health epidemiologist and research chair in university teaching at the University of Ottawa. Here's your dose of smart advice. H5N1 influenza A is called avian flu because it primarily infects birds. It's been showing up in other species, for example, the recent outbreaks in cattle in the U.S. Experts say that strains of pandemic flu typically show up first in animals and then jump species to humans. Cattle are unlikely to kick start a new human pandemic strain, but pigs could. Pigs infected with both human and avian flu at the same time are quite adept at swapping genetic material between the two viruses. In that way, the human flu virus becomes more infectious and more deadly in the process. For H5N1 to cause a pandemic, it has to be able to pass from human to human. So far, that hasn't happened. But humans have been infected with H5N1. Recently, the U.S. Centre for Disease Control reported that a person in the United States tested positive for H5N1 after being exposed to dairy cattle in Texas that were presumed to be infected with the virus. Both the Centre for Disease Control and the World Health Organization say more than 800 people have been infected with H5N1 since 2003. Of those, more than half have died. A case fatality rate like that is almost unheard of when it comes to flu. Experts have suggested that the case fatality rate may be closer to 14 or 15%, which is still a high rate. Unlike COVID when it first arrived, scientists already know a lot about H5N1, so it's less mysterious. H5N1 vaccines have been developed for use in poultry. Some vaccines have been developed for humans. These vaccines have been shown to produce antibodies against H5N1. What we don't know is how effective they would be in an actual outbreak. Antiviral treatments such as oseltamivir or Tamiflu appear to be effective in humans who have been infected with avian flu. And Health Canada says you can reduce your risk of H5N1 from farm products. Make sure the foods you eat are thoroughly cooked and the milk you drink pasteurized. H5N1 isn't something to be worried about, but rather, something to be prepared for. That means good surveillance and testing in animals and people. It means having a solid pandemic plan that includes building stockpiles of vaccines. If you have topics you'd like discussed or questions answered, our email address is thedose@cbc.ca. If you liked this episode, please give us a rating and review wherever you listen. This edition of The Dose was produced by Sameer Chhabra. Our senior producer is Colleen Ross. The Dose wants you to be better informed about your health. If you're looking for medical advice, see your health care provider. I'm Dr. Brian Goldman. Until your next dose.

Back To Top »

Provide Transcript Feedback

CBC would like to acknowledge the support of the Broadcasting Accessibility Fund.

What's going on with H5N1 bird flu? - Transcript

More Stories Like This