Science Friday
Hosted by Flora Lichtman and Ira Flatow
This week, the U. S. reported its first human death from bird flu amid a rise in cases globally.
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This is Science Friday. I'm Ira Flatow.
And I'm Flora Lichtman. Today in the podcast, should we be preparing for a bird flu pandemic?
What I have been trying to focus on is to get us to where we're not at a March 2020 situation. You know what I'm saying?
Thank you.
Yeah, I have young kids. I don't want to be in a lockdown again. Like, nobody does.
This month, the US reported its first death from bird flu, a patient in Louisiana. Back in November, a teenager in Canada was hospitalized and in intensive care with the virus. And last year, more than 60 people were diagnosed with the virus in the US, according to the CDC. That's up from just one case in 2022. Now, just to add a little context, H5N1 avian influenza has been circulating globally in birds and even some mammals for many years. But alarm bells went off when the virus turned up in dairy cattle last year. And since then, over 900 herds have been affected, according to the CDC. So I'm sure many of us are having COVID flashbacks.
I know I am. But is that the right way to think about this? How alarmed should we be? What steps should we be taking? Here to tell us more are two influenza experts who have been following the situation closely. Let me introduce my guests. Dr. Seema Loktawala is co-director for the Center for Transmission of Airborne Pathogens and associate professor studying influenza viruses at Emory University in Atlanta. Dr. Richard Webby is the director of the WHO Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds, and a virologist at St. Jude's Children's Research Hospital in Memphis, Tennessee. Seema, Richard, welcome to Science Friday.
Thanks. I'm glad to be here.
Well, thanks. Thanks for having us.
So this question is for both of you. Just top level, how alarmed are you? Where are you both on the pandemic alarm bell scale? Seema, let's start with you.
On the pandemic risk portion of this, I'm at a moderate level. So moderate risk of it becoming a pandemic right now, in that where it is in its current form. But in my own aspect of where I am, I'm on high alert, the possibility of a pandemic, more so than I think I've been in the past.
Okay. Richard, what about you?
Yeah, it's a tough one. But I think I'm, yeah, somewhere similar to Seema. I'm not on the sort of pack my bags, ready to head to the hills stage. But my sense of unease has increased a little bit over the past six weeks or so from where we were before. Just, just with what this virus has been doing and, and some of the things we've been seeing.
Well, I want to get into this. I mean, we've been tracking H5N1 bird flu for decades. What's happened recently that is making you concerned?
So we know some of the changes this H5 bird flu virus has to make to switch from being a, you know, what is essentially is a bird virus to being a human virus. And I was a little bit reassured. I guess prior to the beginning of the holiday season that, you know, we really hadn't seen much evidence that the virus was making those changes that were required for that host switch. But then, you know, investigators showed that we're one mutation away potentially from a virus that bound better to the human cell than the avian cell. Before that, I probably would have put money on it being two or three changes.
So that information and then the sequencing of the virus from the case both in Canada and Louisiana suggested that the virus was making some changes in some of these areas of the genome that we know were important for this receptor switch as well.
We are seeing that already. And were we seeing those in the wild strains or were they happening within the body of these patients?
We can't answer that with a hundred percent certainty, but I think most of the evidence suggests that these were mutations that were actually made during replication in the people.
Seema, what about you? Do you feel the same as Richard that sort of the last six weeks have raised new alarms?
Definitely the last six weeks, and I would say actually maybe starting in September, October, I've increased my alarm and it's not necessarily for the same reasons Richard said, some are similar. Really, for me, it's the lack of a very strong response. You know, we've known about this outbreak in cattle has been there since April. You know, we're 10 months in and we don't know the full extent of the outbreak. And the lack of, you know, having a really strong plan in place, having seen a lot of traction from a response perspective increases my concern because now we're in flu season. Now we're in the time of year where we know influenza viruses transmit more efficiently between people.
Like Richard, I also agree that the, you know, cases in Canada and in Louisiana are concerning. I'm less concerned about the switch and receptor preference because it's something we expect to happen every single time the virus is in a human. It has the potential to adapt and it's constantly adapting.
You know, this virus has been showing up in sea lions and foxes and cats and cattle. Are the strains circulating in these different groups of animals? The same? Are they different?
You can think they're all H5 viruses, they're all H5N1 viruses, but they're all different sort of combination of other gene segments. So, no, they're not the same virus and they probably have different properties, but we're, you know, we're, I think, just starting to try and understand that.
Well, that was my question. Are the strains equally likely to infect humans now? And are they, you know, do people have the same response to the different strains?
I think probably if you ask 10 influenza virologists, you'll get six different answers on that one. The truth is, no, probably they're not the same. But, you know, it's something we need to do a better job of is understanding what happens with different combinations of genes.
Yeah, I absolutely agree with Richard. You know, you're going to get lots of different opinions on this because we don't have really great experimental data on it. What we do know, though, is that the cases from individuals who have worked in dairy parlors have been more mild in their presentation. And so the Louisiana case and the Canada case that tended to be more severe, obviously Louisiana case was fatal, is a different part of the family tree than the cattle virus.
Are those cases thought to come from birds?
Yes. So the Louisiana case and the British Columbia case are thought to be interactions with, I believe, migratory birds, so wild birds. That, I think, is really interesting for researchers like me and Richard, where we want to understand, you know, what's driving those differences in the presentation.
Well, this maybe gets to my next question. I mean, if we look at global infections in humans of bird flu over the last two decades or so, historically, it's been quite severe, like nearly half of the 900 reported cases in people resulted in death. But of the dozens of people who've been infected in the US last year that we know of, anyway, you know, most cases seem pretty mild. So what's up with that? What's going on there?
Yeah, I mean, I think this is probably due to a variety of factors. One is, you know, something that my lab has been studying is preexisting immunity in that some level of immunity that we've acquired in the more recent decades perhaps is providing some level of cross-protection to reduce the severity of disease, again, not against protecting against infection. It could also be, of course, the route of inoculation that these individuals were exposed to, that the dose in which they inhaled, or where it splattered on their eyes. We're talking about mostly dairy workers here or the poultry workers. Or it could be something about the virus itself. The other aspect could be that in the past, we've missed other infections that were more mild, and we're just capturing the ones that were more severe.
Richard, we talked to you in the summer of 2023, so, you know, a year and a half ago now. And you told us that as a human, it's, it was very difficult, it's very difficult to catch this virus. Is that still true?
Yeah, no, I think it is. Particularly, let's think about even the, what's going on in the dairy cattle right now. We know there's ridiculous amount of virus in the milk of an infected cow. Yeah, so the workers in these milking parlors are getting, you know, exposed to a lot of virus. And yes, we're probably missing a good percentage of those. But, you know, this is a virus that still would prefer to be replicating inside a bird than certainly a human.
Richard, you said that cows are carrying a lot of the virus. How much is a lot?
So if you, you know, think of a 10 with eight or nine zeros after it, that's how much per mil of milk out of these cows, so.
Is that a lot? I don't, I don't have a frame of reference, right?
Yes, I was, I was gonna say, you know, you can probably take 10 virus particles or less to infect a mouse in an experimental study. And so, you know, that's a lot of doses to infect a lot of different animals. If you're a flu virus, an H5N1 flu virus, it seems that the outer of a cow is a great place to be.
I think this is where maybe Richard and I disagreed just a little bit. Because I agree with Richard when he said in 2023, absolutely. Then the risk was really low, right? Because we're not around birds a lot. We're not around seals. But with cows, the interface with humans is really high. There's a lot of interactions. And as Richard just said, there is so much virus. I mean, I think as virologists, we are shocked at the amount of infectious virus, like 100 million particles per little milliliter of milk. And they're milked two to three times a day. And every cow in a dairy parlor, for most dairy parlors, I'm not saying everyone, their teats are cleaned by hand by a person.
And then their teats are force stripped, which means like, you know, squeezing them to initiate the letdown. And so these individuals are exposed to a lot of potential virus in this milk, as well as in people in processing facilities. So to me, I agree. Like, I, you know, I think this is why we've seen so many more infections in 2024 than we saw in 2023. And a sero survey from the CDC said that, you know, 7% of dairy farm workers were seropositive for H5 antibodies. And so I do think we're missing a lot of infections. And the reason I think that's important is because every time this virus gets into a human,
it has the potential to gain properties like Richard described about the receptor binding, but also other ones that we know are important for transmission, or we think are important for transmission, or properties that we don't even know are important for transmission, but are important. And that means it has the potential to continue to spread in humans.
We're going to take a quick break. But when we come back, what actions should we be taking?
Like, testing. There is not universal testing of bulk milk tanks.
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Seema, you know, I think a lot, like I said in the intro, I think a lot of people are thinking about this in terms of COVID, our, you know, our most recent pandemic experience. And I guess, what will a March 2020 look like for bird flu? Like, how will we know we're there? And is that even the right question to be asking?
You mean like when we all went into lockdown until March 2020?
I mean, yeah, like when we knew that this was a disaster, when like we widely knew this is a bad situation.
I think it's definitely going to have a lot more human infections, of course. That's probably going to be when we have maybe a March 2020 like situation. I think what I have been trying to focus on since I heard about this outbreak is to get us to where we're not at a March 2020 situation. You know what I'm saying?
Thank you. Yes.
Yeah, I have young kids. I don't want to be in a lockdown again. Like, no, nobody does. Nobody wants this virus to succeed in humans. Absolutely not. And so, one thing that I have been surprised by is that we haven't taken stronger steps to control the virus in the source.
What should we be doing? Walk us through it.
In my opinion, some of the things we should be doing, one is a stay-at-farm order. You know, cows are transported so much in this country, more than I ever imagined. And they are transported across farms within a state. They are transported across state lines. So we are getting a lot of spread of this virus because cows are being transported that are not known to be infected. So one, number one, is a stay-at-farm order. Because if we can do a stay-at-farm order, maybe we can then go in and assess the extent of this outbreak across every state in the US, across every herd. And so that we actually understand how big... Is this outbreak in cows?
Like, we don't even know that at the moment.
Oh, we don't even know that. No, we don't even know that.
When we say 900 herds, that's not actually a meaningful number.
That's only 900 herds in the States that are testing.
Okay.
Talking about COVID flashbacks, like testing, there is not universal testing of bulk milk tanks. Let's not even talk about individual cows at the moment, of bulk milk tanks across the US. That's not happening. And then, once a herd is positive, there is no information of which cows or how many cows on that herd are positive. And so, let's say the initial outbreak is 10% of the herd and 90% of that herd is not infected.
We're then just letting that virus spread to all of these susceptible, potentially susceptible cows.
Right. There are interventions we could be taking, is what I mean.
There are interventions we could be taking. So, of course, like, you know, PPE is also important. I have been to a number of dairy farms and I will be honest, I see a lot of farm workers wearing gloves, but not a lot wearing eye protection or respiratory protection. And so, that is a concern, of course. So, PPE could be enhanced and requirements around that could be enhanced. And vaccination, you know, this is really Richard's wheelhouse, you know, this is what he does. And there are stockpiled H5 vaccines.
Yeah, I think it makes a lot of sense to be at least offering the H5 vaccine we do have to these workers. Yeah, of course, offering it and actually getting into people's arms are two different things. I think there's a good experience from Finland where they actually did this. So, they tried to vaccinate workers involved in the fur industry over there. They got an abysmal uptake of vaccine in those workers. So, I think it's a good idea to offer it, but, you know, there's going to be, have to be a lot of outreach. It's got to have to be people who have the trust of the individuals working on these farms that says, say, "Hey, vaccination's a good thing. It's going to protect you. It's potentially going to protect your family." But, so, yeah, it's not something we can say, "Let's vaccinate and we're going to get, you know,
90% of these people vaccinated tomorrow." But I think it's something we absolutely should be thinking about.
Is there anything individuals should be doing? Should I get rid of my bird feeder? You know, is there something that I should do to keep myself safe?
So again, from my perspective, I, you know, I think you're probably fine with a bird feeder in the backyard, but you've, you've got to try hard to catch. I think that's, you know, probably still the case. So from a bird feeder in the backyard, the risk, you're, you're raising your risk minimally. But I, again, we've got to think this virus is widespread. It's widespread in wild animals that potentially, if your cat goes in and out, that cat could interact with wild birds. So you've just, I think people have got to be aware of the fact that the virus is out there. If you see something that looks sick, doesn't look right, you know, certainly if, if it's not your own cat, take a wide berth. If it is your own cat, you know, just think about that as well. Um, you know, perhaps wear a little foot gloves, wash your hands type things, talk to your vet. I say the cat, um, but there's lots of other animals as well.
Be careful with your sea lion. Yeah.
If you've got a sea lion out in your backyard, yes, absolutely. Just take, take note if it starts to sneeze.
Sima, any last thoughts?
Yeah, I'd add to Richard's like caution. Also, don't drink raw milk. Don't eat raw cheeses. Uh, it's not something that normally should be advised anyways, but really now, uh, it could be a, a way to have increased exposure to H5 and infection potential. And yeah, don't, don't, don't handle any dead animals or sick animals that you see lying around.
You know, people have been studying these H5 viruses since they really first emerged in 9097. And this batch of viruses that's circulating globally and, you know, in our own backyard now, probably are the nastiest virus that we've seen in terms of ability to cause disease, you know, either in laboratory model systems or, you know, you think of the, the mass die-offs we've seen in the sea mammals, um, the number of birds that are falling out of the sky. So yes, hard to catch, but it's a virus that has a scary ability to cause severe disease. So, you know, I can't say 10 people drinking more raw milk, they're all going to get sick. But having seen what this virus can do, I surely won't be drinking any.
That was very informative. Thank you both for joining me.
Yeah, thanks, Laura.
Thank you so much for having us.
Dr. Sima Loktawala is co-director for the Center for Transmission of Airborne Pathogens and associate professor studying influenza viruses at Emory University in Atlanta. Dr. Richard Webby is the director of the WHO Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds and a virologist at St. Jude's Children's Research Hospital in Memphis, Tennessee.
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