October 5, 2023 • 27 mins
What risk does H5N1 pose to humans? We hear from David Quammen, author of “Spillover,” about the vast and complicated interplay between influenza, the environment, animals, and humans. Then, molecular virologist Wendy Puryear helps us understand why seals on a remote island can be an early warning system.
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Episode Transcript
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Speaker 1 (00:03):
Over the past year, a particular strain of the flu
has been making headlines around the world.
Speaker 2 (00:08):
Some types of bird flu exists harmlessly in wild birds,
but a new, highly contagious strain is fatal to chickens
and it's spreading around the US. New reports from January
document millions of infected birds in nearly every state.
Speaker 1 (00:22):
Despite its name, this bird flu has not stayed in birds.
It's known as H five N one, and in the
US alone, it's been found in bobcats, bears, dolphins, foxes, skunks,
and otters. And as the list of infected mammals keeps growing,
humans are getting nervous because bird flu sometimes does make
(00:42):
its way to people, and when that happens, it can
be deadly. So today we're going to try to understand
where the flu comes from, how it jumps from species
to species, and what this all means for humans. Also,
we'll hear an account from the front lines of influence
of research, And by front lines, I mean a little
(01:03):
island in the North Atlantic that's full of seals.
Speaker 3 (01:08):
You've got a bunch of scientists all geared up in
our field gear and we are crawling through army crawl
style through the dunes to sneak up on a seal pup.
It can be somewhat comical if you didn't know what
was going on.
Speaker 1 (01:24):
I'm Jacob Goldstein. This is incubation. Okay, you ready, Let's
talk about viruses.
Speaker 4 (01:34):
Okay, let's talk about viruses.
Speaker 1 (01:37):
For today's episode, I called up David Kwalman. He's a
journalist who writes about ecology and evolutionary biology, and he
wrote a book called Spillover Animal Infections and the Next
Human Pandemic. David has spent years tracking viruses like the
flu across animal species and he's documented their spillover into
the human world. I'd like to talk about when people
(01:58):
figured out that flu was a disease of birds.
Speaker 4 (02:02):
Yes, there is a wonderful eminent influenza scientist and physician
named Rob Webster, originally a New Zealander who has been
at Saint Jude's Memorial Children's Hospital for most of his
career studying influenza, and back in the nineteen sixties I
(02:23):
think it was nineteen sixty seven, he and a friend
of his were walking along a beach in Australia and
they found a bunch of dead birds lying on the beach. Shearwaters.
What killed all these birds all of a sudden. Well
then they wondered whether, I don't know, could it have
been maybe an influenza. Maybe we should do a little
(02:45):
research on that. So they went to their boss and
they said, we want to go to the Great Barrier
Reef and live on an island for a few weeks
and sampled dead birds and any birds that we can
catch and see if we can find influenza. And their
boss happened to know that Webster was a passionate sport fisherman,
(03:09):
and he looked at these two young guys and he says,
you guys are delusional. Webster told me that verbatim. He said,
this man looked at them and said, you guys are
delusional if you think I'm going to pay for you
to go and live on an island off the Great
Barrier Reef and fish. But they persist, and eventually they
get a small stipend for the who so they go
(03:31):
out there and do this research and they find flu
in birds. And from that effort and a lot of
research that followed after it. But thanks largely to Rob
Webster and his friend, we know now that all of
(03:54):
the human influenza A type viruses that infect us come
from wild aquatic birds.
Speaker 1 (04:03):
Huh. And to ask sort of the dumb question, why
is that important? Why is that a big deal?
Speaker 4 (04:09):
Well, with any sort of viral threat that's getting into
humans periodically, dramatically, murderously, it's important to know how how
is that getting into humans, so we can prevent them
from getting into us.
Speaker 1 (04:26):
So let's talk about H five N one. It's been
around for a while.
Speaker 4 (04:30):
Right, This version of H five N one has been
around since nineteen ninety six. It was found killing some birds,
and then in two thousand and five it killed a
large number of bar headed geese at a place called
Chinghai Lake in western China. From there it has gone
from infecting wild birds to infecting domestic birds and then
(04:55):
infecting mammals.
Speaker 1 (04:57):
I want to just talk for a minute about the
influenza virus. It's interesting, right, It's interesting how it works,
how it functions. So just like, tell me about the
influenza virus.
Speaker 4 (05:08):
The influenza viruses belong to a family of RNA viruses,
meaning that their genome, the little information molecule inside the
protein capsule of the virus, is written in the molecule
RNA rather than DNA. DNA is the famous double helix molecule.
(05:29):
It's very stable, it has self repairing mechanisms, and so
when it copies itself, it corrects its mistakes, doesn't make
very many mistakes. When RNA, a single strand of RNA
copies itself, it makes a lot of mistakes. RNA viruses
evolve quickly and are capable of jumping from one kind
of host into another. The influenza viruses also have another trick.
(05:52):
They have segmented genomes. So their genomes twelve to fourteen
thousand letters of RNA is segmented into eight segments that
pop apart between one and the next. So imagine an engine,
a locomotive, and six box cars and a caboose, and
(06:13):
that's your influenza virus.
Speaker 1 (06:16):
So now we have this virus, the flu virus, and
the whole genome can change quickly and does change quickly
because it's RNA rather than DNA. And on top of that,
you have this sort of segmented you know, railcar like
nature that allows for kind of rapid change as well.
Speaker 4 (06:36):
And that rapid change is accomplished by swapping of pieces
with other viruses. If two different particles of influenza replicate
themselves in the same cell at the same time, then
there is this event, this trick called reassortment that can occur.
Speaker 1 (06:54):
And that reassortment is really bad for say, our immune system. Right,
and suddenly we've never seen anything like this one before.
Speaker 4 (07:04):
That's right, that's right. And so why does a virus
get called H five N one? The numbers refer to
the fact that there are you know, fifteen or twenty
variations of the possible H segment and a number of
other possible variations of the end segment. So you have
H five N one, H two and nine, and the
(07:27):
H and the end.
Speaker 1 (07:27):
Are proteins that are on the surface of the virus, right,
and so that our immune system record, that's correct. So okay,
so we have this virus. It has this ability to
change very quickly. How does it go from species to species?
We know that it's largely in birds. How does it
move among species?
Speaker 4 (07:49):
Well, by contact is the first answer to that. That's
the ecology side. A wild bird becomes infected with an influenza,
let's say a duck, a wild duck. Rob Webster says,
the duck is the trojan horse when it comes to
bird flu avian influenza.
Speaker 1 (08:09):
Like it I like a semi mixed metaphor.
Speaker 4 (08:13):
What he means by that is it's the secret carrier.
When a duck becomes infected with avian influenza at least
many types of avian influenza, it doesn't show symptoms, it
doesn't fall down. It continues to migrate and congregate with
other birds, carrying the virus and pooping it out into lakes, ponds,
(08:37):
streams wherever it goes, depositing this little gift of virus,
and other birds then are susceptible to that virus when
they pick it up. And then if your chickens and
your geese start to fall dead, you might think about
that trojan horse in the form of a duck that
came through and brought that virus.
Speaker 1 (08:58):
Okay, so now it's gone from bird to bird. How
does it go from bird to mammal?
Speaker 4 (09:03):
A virus such as influenza gets into animal cells by
attaching to particular receptors on the surface of those cells.
In birds, it attaches to a particular kind of receptor.
Humans have a different kind of receptor. Pigs have both
(09:24):
the bird like and the mammalian receptor. So a pig
can become infected with a virus that is adapted to
attaching to the bird receptor, and then while it's multiplying
in the pig, that virus can evolve to be able
to attach also to the mammal type receptor. When it
(09:45):
comes out of the pigs, it's capable of infecting humans.
Speaker 1 (09:49):
Ah, so it's easy for a pig to get bird flu,
and pigs are this sort of mixing vessel basically, where
a bird flu can mutate into a flu that can
infect other kinds of mammals, including humans. That's right, Okay,
So I think now we have a really good base
(10:11):
of knowledge to talk about H five N one, this
strain of flu that is currently infecting birds. First, tell
me the scope of it, like how much is it
infecting birds? How many birds is it infecting?
Speaker 4 (10:28):
Well, this version of H five N one for the
last couple of years has been circling the planet. It's
probably killing millions of wild birds. And if and when
it gets into those bird species, wildbird species that are endangered,
like the hooping crane with nine hundred individuals on the planet,
(10:51):
or the California condor with maybe three hundred individuals, it
has the potential to knock those out entirely, to drive
both of those species over the brink of extinction.
Speaker 1 (11:04):
You've described what's happening with age five in one as
a kind of pandemic that is happening right now.
Speaker 4 (11:10):
Yes, for birds, For wild birds, it's a pandemic, and
for domestic birds it's a pandemic. If you have a
million chickens on a poultry farm and the bird flu
comes in by way of a duck that happens to
come and poop in their water trough and some of
those chickens get infected, that virus can spread through those
million chickens very quickly, which means billions and billions and
(11:34):
trillions and trillions of viral particles replicating. Each time the
virus replicates itself, there's a potential for it to make mistakes,
to have a mutation, a random mutation, and several of
those random mutations can create a virus that can infect
(11:55):
the guy who's cleaning out the cages. So the fact
that we have thirty three billion chickens on this planet
at a given moment means that there is this huge
petri dish for the encouragement of evolution in the bird
flu virus. Millions of birds in poultry operations around the
(12:18):
world have either died or been killed preventively to stop
the spread of this this virus in commercial operations.
Speaker 1 (12:27):
And infections of people have been thankfully rare so far, Yes,
they have been rare. Right And crucially, there's no evidence
that it can go from person to person. It just
goes from bird to person when people are working very
very closely with birds.
Speaker 4 (12:41):
So far, Yes, that is being watched very carefully, although
probably not as carefully as it should be watched. There
is such a randomness, such an element of randomness involved
in influenza evolution, that you can know what its capacity
to evolve quickly is, but you can't say what's going
(13:06):
to happen tomorrow.
Speaker 1 (13:08):
Plainly, the terrible day that we hope will not come
is when there is demonstrated human to human transmission of
H five and one short of that, what should I
look out for, like, as a person who wants to
be well informed about this, Like, what's the signal that
I need to, you know, buy some bottle of water
(13:31):
and lock the door.
Speaker 4 (13:32):
Well, one of the signals that is increasing in volume
is the infection of mammals with H five N one
bird flu. So when you see another story about well,
bird flu just killed another porpoise, bird flu just killed
another dolphin, another seal. That is a warning alarm, and
(13:57):
the more it happens, the loud of the alarm gain.
Speaker 1 (14:06):
We'll be back with more in just a minute. My
guest for the second half of the show is Wendy
per Year. She's a molecular virologist at the Coming School
of Veterinary Medicine at Tuffts University and her job is
(14:28):
looking out for that key warning sign that David Kwaman
was talking about. She studies wild mammals to try and
detect when they're being infected with H five N one.
Speaker 3 (14:38):
It's H five N one two three four four B.
It's like it's very it just rolls off the tongue right.
Speaker 1 (14:44):
Wendy told me about a moment last spring when she
got an alarming phone call. It came from Linda Dohity,
who runs an organization called Marine Mammals of Maine.
Speaker 3 (14:52):
So she called me as I was pulling into my
parking spot and she's like, Wendy, I think we might
have a problem. We have some seals that are are
coming in. They're showing really strong respiratory signs like I'm
really nervous that high path has arrived here in the seals.
Speaker 1 (15:11):
High path means high pathogenicity, which means bad flu strains
like H five N one.
Speaker 3 (15:17):
Honestly, this kind of felt like our mission impossible moment,
so I instructed her to overnight samples to me. So
she has all of the supplies in house there of
the different vials that we need, and it's really it's
the same exact stuff that we all have used doing
COVID screening, so it's you know, they get swabbed, it
(15:38):
goes into a viral transport media into a little tube, but.
Speaker 1 (15:41):
From a seal, so they're sticking like a Q tip
up the seals nose.
Speaker 3 (15:45):
Yes, so we stick Q tips up the seals nose.
So we do nasal samples and rectal samples, which thankfully
we haven't done with humans. And those all came to
me overnight and we immediately ran those samples as soon
as they arrived here in the lab, and we detected
a really strong signal for the H five N one
(16:07):
for the high path influenza.
Speaker 1 (16:11):
Whendy ran the tests again just to make sure, and
she got the same result. H five N one had
made its way to seals along the coast of Maine.
She sounded the alarm, notified the FEDS, and fortunately this
outbreak passed pretty quickly, but Wendy and other scientists are
still worried about future outbreaks. Let's just talk about why
this moment is a big deal, Like, why is this
(16:33):
such an important moment?
Speaker 3 (16:34):
So one of the major reasons is that there's a
lot of different forms of influenza that circulate in wildlife,
but when it makes that shift into mammals, because it's
usually circulating in birds, and when it shifts over into mammals,
obviously we're a mammal. So that means it is one
step closer to being of concern for human health and
pandemic potential.
Speaker 1 (16:54):
It's basically it's just getting closer to us in a
biological sense exactly.
Speaker 3 (16:59):
Yeah, they're all been referred to as a as a sentinel.
They're able to give us a heads up of what
sort of things might be moving from birds into a mammal,
But not to say that the seals themselves aren't. For
it's not just about the human health. So it's also
that you know, there is concern that it was going
to have a very large impact on wildlife as well,
because this is a whole new virus that is going
into a species that hasn't seen this virus before, so
(17:23):
potentially they don't have the immune protection in place to
be able to handle that. So it's human health, it's
the animal health, it's all of it.
Speaker 1 (17:30):
How do marine mammals get a hive in one this
high path flu That.
Speaker 3 (17:34):
Is an excellent question and that is one of the
things that we are actively still trying to find out.
So there are a couple of different ways. It seems
pretty clear it's coming from wild birds. So the bird
is where the virus is circulating and it spills over
and makes its way into seals. So the question is
how exactly it could be the case that the seal
(17:55):
is actually consuming an infected.
Speaker 1 (17:58):
Bird, eating it, yeah, eating it, Yeah.
Speaker 3 (18:01):
And that's what we've seen a lot of terrestrial mammals
that that seems to be.
Speaker 1 (18:04):
How I mean, do seals eat birds well.
Speaker 3 (18:08):
In some cases, yes, but it is not It certainly
is not a common thing on their their venu and
given the number of seals that we saw with high
path influenza, it seems very unlikely that each of them
were having the unusual meal of a bird, so it
is it's the highest probability in my mind, is that
(18:29):
the virus is being shed into the environment and that
the seals are coming into contact with it, whether it
is bird poop on the beach and they're you know,
ingesting it or inhaling it that way, or we see
little bodies of water where birds are pooping in the
water there and the seals are then hanging out in
that water too, So that's certainly possibility.
Speaker 1 (18:51):
I mean, it's worth noting that with birds, flu, unlike
in humans, is is a fegal oral. It's a like
a gas through intestinal right right exactly.
Speaker 3 (19:01):
That's an important point. So in birds it's a it's
a gi so it's they're they're shedding it in their
feces and.
Speaker 1 (19:07):
That's how birds spread it to each other like humans
get some diseases that way, like from drinking dirty water,
and that's the way flu works for birds, but not
for people exactly.
Speaker 3 (19:18):
Yeah, so it's possible that that's how it's getting into
seals as well. Okay, it's also possible that the seals
are spreading amongst themselves once it gets into that population,
and that's something that is still being very actively looked at.
It's not clear yet, it's not really ruled in or
ruled out.
Speaker 1 (19:35):
I mean, you mentioned that just kind of like as
one of several options. But that's a huge, huge, high
stakes question for people, right, Like the virus going from
birds to seals is way different than the virus going
from mammal to mammal. Right, that is a huge, huge,
profoundly important public health question. It absolutely is. I'm shocked,
(19:58):
frankly that we don't know the answer. Scared, Yeah, I know.
Speaker 3 (20:01):
But the thing is is it's not an easy answer
to get because you need a pretty sizable data set
to really be able to say anything with confidence. And
the number of sequences that we were able to get
from viruses off of seals is a small enough number
that the data is still not clear. It's not really
convincing one way or the other.
Speaker 1 (20:25):
So, Okay, that's the sort of abstract, high level story.
I also want to talk about your field work. As
I understand you go out and basically hang out with seals.
Tell me about that.
Speaker 3 (20:37):
So we have several different sites around the Gulf of Maine.
The primary one that I personally go to is Montomoy,
and that is off of Cape Cod, Massachusetts.
Speaker 1 (20:46):
What part of the year do you go to Montomoy?
Speaker 3 (20:48):
The time when everybody wants to go to the islands
off of Cape Cod in the middle of the winter
January and February. Montamoi is one of my favorite places
on the planet. Though it's off of Cape Cod, it's
very remote there is there's there are no developments there,
there's no heat, electricity, running water. The boats go and
(21:09):
drop us off and we have whatever food and water
and safety gear we brought with us. And there is
an old lighthouse there. It's actually two hundred year old
lighthouse just had its anniversary. It hasn't been operational for
the last hundred years. So the Park Service is very
gracious in letting us use that as basically a base camp.
Speaker 1 (21:28):
And it's you and a few researchers and how many seals.
Speaker 3 (21:31):
Oh, lots of seals. So in the region, it's estimated
that there's probably about fifty thousand, but on Monomoy we're
talking a couple of thousand at that period of time.
Speaker 1 (21:41):
That's a lot of seals, A lot of seals. I mean,
what's it smell like?
Speaker 3 (21:48):
So the very first time that I went out to Monomoy,
we're all geared up and we land on the beach
and we start to walk over to the seals, and
there's this pungent smell of skunk, and I was like, oh,
somebody must have been spray I by skunk on there
like their field clothes, and we're just none of us
are talking about it, so I'm just gonna We're just
going to carry on. And then eventually I came to
realize that no, no, that muskie smell, that is the
(22:09):
smell of the seals. So it smells very similar to
skunk in my opinion.
Speaker 1 (22:14):
What do they sound like? Is it loud like you
hear like a thousand seals going off.
Speaker 3 (22:20):
During the day, Typically not at all unless they're they're
kind of bickering and fighting and having some territorial little battles.
At night time, it's sort of a consistent, low bellowing
that you hear in the background while you're while you're
trying to sleep. It's actually quite nice ambient noise.
Speaker 1 (22:44):
It does sound a feeling that sounds better than the
smell certainly right. So so you're out there, what do
you do?
Speaker 3 (22:52):
We are going out and actually capturing the pups, and
we focus on the pups because they are, give take,
about one hundred pounds as opposed to the adults, which
can be around eight hundred pounds. So we're able to
physically restrain the pups. And that's why we're there during
January and February because that's the pupping season. It can
be somewhat comical if you didn't know what was going on.
(23:14):
You've got a bunch of scientists all geared up, and
we are crawling through army crawl style through the dunes
to sneak up on a seal pup and put this
bag over the seal that we then capture it, and
we're doing sample collections. We're doing measurements to look for
just the overall health of the animals, and then we
(23:37):
put a tag on them. In some cases we put
on a satellite tag so we can actually follow their
movement and then we release them and all of that
can happen and as quickly as six minutes, and then
we max it out at twenty minutes. So if we
hit twenty minutes, we release the seal.
Speaker 1 (23:54):
So when you go out in the winter and you
are swabbing baby seals, like you are doing the sentinel work,
you're like out there looking for H five in one
to be the early warning system for the rest of us. Exactly.
Speaker 3 (24:09):
We are trying to pick up anything that might be
developing the ability to go from birds to mammals and
then trying to figure out is that something that then
presents the possibility that it could then come into humans
or other wild mammals, but mammals in general.
Speaker 1 (24:26):
So if I hope not, When let's say, if someone
finds a clear instance of H five in one spreading
from mammal to mammal, what will that mean?
Speaker 3 (24:41):
That is the point where we collectively need to get
much more serious about preparing for it. The good news
with high path influenza is I like to say, it's
not COVID, so it's we see it coming. We know influenza,
we have vaccines against influenza. We have seed stocks that
(25:02):
are maintained to be able to rapidly grow up vaccines,
so we have the capacity to respond. It's important that
we continue to do very robust surveillance so that we
know if or when these changes happen, and what exactly
they look like.
Speaker 1 (25:18):
I will say, after talking to you about what's happening
with H five N one and mammals, I'm certainly not
not worried, but I am less worried than I was
before I talk to you.
Speaker 3 (25:31):
Excellent. I like to think that we will be prepared
for the human health side of things, that we will
be prepared to respond pretty efficiently and pretty rapidly should
it become a concern for human health. My bigger concern
is for wildlife. That's a much trickier one for us
to be able to mitigate, and it could have a
(25:54):
very long lasting, very negative impact to several wildlife species.
But I think from human health we will be able
to hopefully respond well.
Speaker 1 (26:04):
I appreciate all your time.
Speaker 3 (26:05):
Yeah, absolutely.
Speaker 1 (26:08):
One last thing. About a month after we spoke with Wendy,
H five N one was detected in seals off the
coast of Washington State. It was the first time AGE
five and one had been detected in marine mammals off
the west coast of the United States. Thanks to my
guest today, David Quarman and Wendy per Year. Next week
(26:29):
we'll be talking about HPV human peppellomavirus and about how
the HPV vaccine explains American's complicated relationship to all vaccines.
Speaker 3 (26:41):
The HPV story is so interesting because support was coming
from everywhere, but backlash was coming from everywhere too, Like
all over the Political Spectrum.
Speaker 1 (26:51):
Incubation is a co production of Pushkin Industries and Ruby
Studio at iHeartMedia. It's produced by Gabriel Hunter Chang, Ariela Markowitz,
and am Gaines McQuaid. Our editors are Julia Barton and
Karen Schakerjie Mastering by Anne Pope, fact checking by Joseph Friedman.
Our executive producers are Katherine Girardeau and Matt Romano. I'm
(27:12):
Jacob Goldstein. Thanks for listening.
Over the past year, a particular strain of the flu
has been making headlines around the world.
Speaker 2 (00:08):
Some types of bird flu exists harmlessly in wild birds,
but a new, highly contagious strain is fatal to chickens
and it's spreading around the US. New reports from January
document millions of infected birds in nearly every state.
Speaker 1 (00:22):
Despite its name, this bird flu has not stayed in birds.
It's known as H five N one, and in the
US alone, it's been found in bobcats, bears, dolphins, foxes, skunks,
and otters. And as the list of infected mammals keeps growing,
humans are getting nervous because bird flu sometimes does make
(00:42):
its way to people, and when that happens, it can
be deadly. So today we're going to try to understand
where the flu comes from, how it jumps from species
to species, and what this all means for humans. Also,
we'll hear an account from the front lines of influence
of research, And by front lines, I mean a little
(01:03):
island in the North Atlantic that's full of seals.
Speaker 3 (01:08):
You've got a bunch of scientists all geared up in
our field gear and we are crawling through army crawl
style through the dunes to sneak up on a seal pup.
It can be somewhat comical if you didn't know what
was going on.
Speaker 1 (01:24):
I'm Jacob Goldstein. This is incubation. Okay, you ready, Let's
talk about viruses.
Speaker 4 (01:34):
Okay, let's talk about viruses.
Speaker 1 (01:37):
For today's episode, I called up David Kwalman. He's a
journalist who writes about ecology and evolutionary biology, and he
wrote a book called Spillover Animal Infections and the Next
Human Pandemic. David has spent years tracking viruses like the
flu across animal species and he's documented their spillover into
the human world. I'd like to talk about when people
(01:58):
figured out that flu was a disease of birds.
Speaker 4 (02:02):
Yes, there is a wonderful eminent influenza scientist and physician
named Rob Webster, originally a New Zealander who has been
at Saint Jude's Memorial Children's Hospital for most of his
career studying influenza, and back in the nineteen sixties I
(02:23):
think it was nineteen sixty seven, he and a friend
of his were walking along a beach in Australia and
they found a bunch of dead birds lying on the beach. Shearwaters.
What killed all these birds all of a sudden. Well
then they wondered whether, I don't know, could it have
been maybe an influenza. Maybe we should do a little
(02:45):
research on that. So they went to their boss and
they said, we want to go to the Great Barrier
Reef and live on an island for a few weeks
and sampled dead birds and any birds that we can
catch and see if we can find influenza. And their
boss happened to know that Webster was a passionate sport fisherman,
(03:09):
and he looked at these two young guys and he says,
you guys are delusional. Webster told me that verbatim. He said,
this man looked at them and said, you guys are
delusional if you think I'm going to pay for you
to go and live on an island off the Great
Barrier Reef and fish. But they persist, and eventually they
get a small stipend for the who so they go
(03:31):
out there and do this research and they find flu
in birds. And from that effort and a lot of
research that followed after it. But thanks largely to Rob
Webster and his friend, we know now that all of
(03:54):
the human influenza A type viruses that infect us come
from wild aquatic birds.
Speaker 1 (04:03):
Huh. And to ask sort of the dumb question, why
is that important? Why is that a big deal?
Speaker 4 (04:09):
Well, with any sort of viral threat that's getting into
humans periodically, dramatically, murderously, it's important to know how how
is that getting into humans, so we can prevent them
from getting into us.
Speaker 1 (04:26):
So let's talk about H five N one. It's been
around for a while.
Speaker 4 (04:30):
Right, This version of H five N one has been
around since nineteen ninety six. It was found killing some birds,
and then in two thousand and five it killed a
large number of bar headed geese at a place called
Chinghai Lake in western China. From there it has gone
from infecting wild birds to infecting domestic birds and then
(04:55):
infecting mammals.
Speaker 1 (04:57):
I want to just talk for a minute about the
influenza virus. It's interesting, right, It's interesting how it works,
how it functions. So just like, tell me about the
influenza virus.
Speaker 4 (05:08):
The influenza viruses belong to a family of RNA viruses,
meaning that their genome, the little information molecule inside the
protein capsule of the virus, is written in the molecule
RNA rather than DNA. DNA is the famous double helix molecule.
(05:29):
It's very stable, it has self repairing mechanisms, and so
when it copies itself, it corrects its mistakes, doesn't make
very many mistakes. When RNA, a single strand of RNA
copies itself, it makes a lot of mistakes. RNA viruses
evolve quickly and are capable of jumping from one kind
of host into another. The influenza viruses also have another trick.
(05:52):
They have segmented genomes. So their genomes twelve to fourteen
thousand letters of RNA is segmented into eight segments that
pop apart between one and the next. So imagine an engine,
a locomotive, and six box cars and a caboose, and
(06:13):
that's your influenza virus.
Speaker 1 (06:16):
So now we have this virus, the flu virus, and
the whole genome can change quickly and does change quickly
because it's RNA rather than DNA. And on top of that,
you have this sort of segmented you know, railcar like
nature that allows for kind of rapid change as well.
Speaker 4 (06:36):
And that rapid change is accomplished by swapping of pieces
with other viruses. If two different particles of influenza replicate
themselves in the same cell at the same time, then
there is this event, this trick called reassortment that can occur.
Speaker 1 (06:54):
And that reassortment is really bad for say, our immune system. Right,
and suddenly we've never seen anything like this one before.
Speaker 4 (07:04):
That's right, that's right. And so why does a virus
get called H five N one? The numbers refer to
the fact that there are you know, fifteen or twenty
variations of the possible H segment and a number of
other possible variations of the end segment. So you have
H five N one, H two and nine, and the
(07:27):
H and the end.
Speaker 1 (07:27):
Are proteins that are on the surface of the virus, right,
and so that our immune system record, that's correct. So okay,
so we have this virus. It has this ability to
change very quickly. How does it go from species to species?
We know that it's largely in birds. How does it
move among species?
Speaker 4 (07:49):
Well, by contact is the first answer to that. That's
the ecology side. A wild bird becomes infected with an influenza,
let's say a duck, a wild duck. Rob Webster says,
the duck is the trojan horse when it comes to
bird flu avian influenza.
Speaker 1 (08:09):
Like it I like a semi mixed metaphor.
Speaker 4 (08:13):
What he means by that is it's the secret carrier.
When a duck becomes infected with avian influenza at least
many types of avian influenza, it doesn't show symptoms, it
doesn't fall down. It continues to migrate and congregate with
other birds, carrying the virus and pooping it out into lakes, ponds,
(08:37):
streams wherever it goes, depositing this little gift of virus,
and other birds then are susceptible to that virus when
they pick it up. And then if your chickens and
your geese start to fall dead, you might think about
that trojan horse in the form of a duck that
came through and brought that virus.
Speaker 1 (08:58):
Okay, so now it's gone from bird to bird. How
does it go from bird to mammal?
Speaker 4 (09:03):
A virus such as influenza gets into animal cells by
attaching to particular receptors on the surface of those cells.
In birds, it attaches to a particular kind of receptor.
Humans have a different kind of receptor. Pigs have both
(09:24):
the bird like and the mammalian receptor. So a pig
can become infected with a virus that is adapted to
attaching to the bird receptor, and then while it's multiplying
in the pig, that virus can evolve to be able
to attach also to the mammal type receptor. When it
(09:45):
comes out of the pigs, it's capable of infecting humans.
Speaker 1 (09:49):
Ah, so it's easy for a pig to get bird flu,
and pigs are this sort of mixing vessel basically, where
a bird flu can mutate into a flu that can
infect other kinds of mammals, including humans. That's right, Okay,
So I think now we have a really good base
(10:11):
of knowledge to talk about H five N one, this
strain of flu that is currently infecting birds. First, tell
me the scope of it, like how much is it
infecting birds? How many birds is it infecting?
Speaker 4 (10:28):
Well, this version of H five N one for the
last couple of years has been circling the planet. It's
probably killing millions of wild birds. And if and when
it gets into those bird species, wildbird species that are endangered,
like the hooping crane with nine hundred individuals on the planet,
(10:51):
or the California condor with maybe three hundred individuals, it
has the potential to knock those out entirely, to drive
both of those species over the brink of extinction.
Speaker 1 (11:04):
You've described what's happening with age five in one as
a kind of pandemic that is happening right now.
Speaker 4 (11:10):
Yes, for birds, For wild birds, it's a pandemic, and
for domestic birds it's a pandemic. If you have a
million chickens on a poultry farm and the bird flu
comes in by way of a duck that happens to
come and poop in their water trough and some of
those chickens get infected, that virus can spread through those
million chickens very quickly, which means billions and billions and
(11:34):
trillions and trillions of viral particles replicating. Each time the
virus replicates itself, there's a potential for it to make mistakes,
to have a mutation, a random mutation, and several of
those random mutations can create a virus that can infect
(11:55):
the guy who's cleaning out the cages. So the fact
that we have thirty three billion chickens on this planet
at a given moment means that there is this huge
petri dish for the encouragement of evolution in the bird
flu virus. Millions of birds in poultry operations around the
(12:18):
world have either died or been killed preventively to stop
the spread of this this virus in commercial operations.
Speaker 1 (12:27):
And infections of people have been thankfully rare so far, Yes,
they have been rare. Right And crucially, there's no evidence
that it can go from person to person. It just
goes from bird to person when people are working very
very closely with birds.
Speaker 4 (12:41):
So far, Yes, that is being watched very carefully, although
probably not as carefully as it should be watched. There
is such a randomness, such an element of randomness involved
in influenza evolution, that you can know what its capacity
to evolve quickly is, but you can't say what's going
(13:06):
to happen tomorrow.
Speaker 1 (13:08):
Plainly, the terrible day that we hope will not come
is when there is demonstrated human to human transmission of
H five and one short of that, what should I
look out for, like, as a person who wants to
be well informed about this, Like, what's the signal that
I need to, you know, buy some bottle of water
(13:31):
and lock the door.
Speaker 4 (13:32):
Well, one of the signals that is increasing in volume
is the infection of mammals with H five N one
bird flu. So when you see another story about well,
bird flu just killed another porpoise, bird flu just killed
another dolphin, another seal. That is a warning alarm, and
(13:57):
the more it happens, the loud of the alarm gain.
Speaker 1 (14:06):
We'll be back with more in just a minute. My
guest for the second half of the show is Wendy
per Year. She's a molecular virologist at the Coming School
of Veterinary Medicine at Tuffts University and her job is
(14:28):
looking out for that key warning sign that David Kwaman
was talking about. She studies wild mammals to try and
detect when they're being infected with H five N one.
Speaker 3 (14:38):
It's H five N one two three four four B.
It's like it's very it just rolls off the tongue right.
Speaker 1 (14:44):
Wendy told me about a moment last spring when she
got an alarming phone call. It came from Linda Dohity,
who runs an organization called Marine Mammals of Maine.
Speaker 3 (14:52):
So she called me as I was pulling into my
parking spot and she's like, Wendy, I think we might
have a problem. We have some seals that are are
coming in. They're showing really strong respiratory signs like I'm
really nervous that high path has arrived here in the seals.
Speaker 1 (15:11):
High path means high pathogenicity, which means bad flu strains
like H five N one.
Speaker 3 (15:17):
Honestly, this kind of felt like our mission impossible moment,
so I instructed her to overnight samples to me. So
she has all of the supplies in house there of
the different vials that we need, and it's really it's
the same exact stuff that we all have used doing
COVID screening, so it's you know, they get swabbed, it
(15:38):
goes into a viral transport media into a little tube, but.
Speaker 1 (15:41):
From a seal, so they're sticking like a Q tip
up the seals nose.
Speaker 3 (15:45):
Yes, so we stick Q tips up the seals nose.
So we do nasal samples and rectal samples, which thankfully
we haven't done with humans. And those all came to
me overnight and we immediately ran those samples as soon
as they arrived here in the lab, and we detected
a really strong signal for the H five N one
(16:07):
for the high path influenza.
Speaker 1 (16:11):
Whendy ran the tests again just to make sure, and
she got the same result. H five N one had
made its way to seals along the coast of Maine.
She sounded the alarm, notified the FEDS, and fortunately this
outbreak passed pretty quickly, but Wendy and other scientists are
still worried about future outbreaks. Let's just talk about why
this moment is a big deal, Like, why is this
(16:33):
such an important moment?
Speaker 3 (16:34):
So one of the major reasons is that there's a
lot of different forms of influenza that circulate in wildlife,
but when it makes that shift into mammals, because it's
usually circulating in birds, and when it shifts over into mammals,
obviously we're a mammal. So that means it is one
step closer to being of concern for human health and
pandemic potential.
Speaker 1 (16:54):
It's basically it's just getting closer to us in a
biological sense exactly.
Speaker 3 (16:59):
Yeah, they're all been referred to as a as a sentinel.
They're able to give us a heads up of what
sort of things might be moving from birds into a mammal,
But not to say that the seals themselves aren't. For
it's not just about the human health. So it's also
that you know, there is concern that it was going
to have a very large impact on wildlife as well,
because this is a whole new virus that is going
into a species that hasn't seen this virus before, so
(17:23):
potentially they don't have the immune protection in place to
be able to handle that. So it's human health, it's
the animal health, it's all of it.
Speaker 1 (17:30):
How do marine mammals get a hive in one this
high path flu That.
Speaker 3 (17:34):
Is an excellent question and that is one of the
things that we are actively still trying to find out.
So there are a couple of different ways. It seems
pretty clear it's coming from wild birds. So the bird
is where the virus is circulating and it spills over
and makes its way into seals. So the question is
how exactly it could be the case that the seal
(17:55):
is actually consuming an infected.
Speaker 1 (17:58):
Bird, eating it, yeah, eating it, Yeah.
Speaker 3 (18:01):
And that's what we've seen a lot of terrestrial mammals
that that seems to be.
Speaker 1 (18:04):
How I mean, do seals eat birds well.
Speaker 3 (18:08):
In some cases, yes, but it is not It certainly
is not a common thing on their their venu and
given the number of seals that we saw with high
path influenza, it seems very unlikely that each of them
were having the unusual meal of a bird, so it
is it's the highest probability in my mind, is that
(18:29):
the virus is being shed into the environment and that
the seals are coming into contact with it, whether it
is bird poop on the beach and they're you know,
ingesting it or inhaling it that way, or we see
little bodies of water where birds are pooping in the
water there and the seals are then hanging out in
that water too, So that's certainly possibility.
Speaker 1 (18:51):
I mean, it's worth noting that with birds, flu, unlike
in humans, is is a fegal oral. It's a like
a gas through intestinal right right exactly.
Speaker 3 (19:01):
That's an important point. So in birds it's a it's
a gi so it's they're they're shedding it in their
feces and.
Speaker 1 (19:07):
That's how birds spread it to each other like humans
get some diseases that way, like from drinking dirty water,
and that's the way flu works for birds, but not
for people exactly.
Speaker 3 (19:18):
Yeah, so it's possible that that's how it's getting into
seals as well. Okay, it's also possible that the seals
are spreading amongst themselves once it gets into that population,
and that's something that is still being very actively looked at.
It's not clear yet, it's not really ruled in or
ruled out.
Speaker 1 (19:35):
I mean, you mentioned that just kind of like as
one of several options. But that's a huge, huge, high
stakes question for people, right, Like the virus going from
birds to seals is way different than the virus going
from mammal to mammal. Right, that is a huge, huge,
profoundly important public health question. It absolutely is. I'm shocked,
(19:58):
frankly that we don't know the answer. Scared, Yeah, I know.
Speaker 3 (20:01):
But the thing is is it's not an easy answer
to get because you need a pretty sizable data set
to really be able to say anything with confidence. And
the number of sequences that we were able to get
from viruses off of seals is a small enough number
that the data is still not clear. It's not really
convincing one way or the other.
Speaker 1 (20:25):
So, Okay, that's the sort of abstract, high level story.
I also want to talk about your field work. As
I understand you go out and basically hang out with seals.
Tell me about that.
Speaker 3 (20:37):
So we have several different sites around the Gulf of Maine.
The primary one that I personally go to is Montomoy,
and that is off of Cape Cod, Massachusetts.
Speaker 1 (20:46):
What part of the year do you go to Montomoy?
Speaker 3 (20:48):
The time when everybody wants to go to the islands
off of Cape Cod in the middle of the winter
January and February. Montamoi is one of my favorite places
on the planet. Though it's off of Cape Cod, it's
very remote there is there's there are no developments there,
there's no heat, electricity, running water. The boats go and
(21:09):
drop us off and we have whatever food and water
and safety gear we brought with us. And there is
an old lighthouse there. It's actually two hundred year old
lighthouse just had its anniversary. It hasn't been operational for
the last hundred years. So the Park Service is very
gracious in letting us use that as basically a base camp.
Speaker 1 (21:28):
And it's you and a few researchers and how many seals.
Speaker 3 (21:31):
Oh, lots of seals. So in the region, it's estimated
that there's probably about fifty thousand, but on Monomoy we're
talking a couple of thousand at that period of time.
Speaker 1 (21:41):
That's a lot of seals, A lot of seals. I mean,
what's it smell like?
Speaker 3 (21:48):
So the very first time that I went out to Monomoy,
we're all geared up and we land on the beach
and we start to walk over to the seals, and
there's this pungent smell of skunk, and I was like, oh,
somebody must have been spray I by skunk on there
like their field clothes, and we're just none of us
are talking about it, so I'm just gonna We're just
going to carry on. And then eventually I came to
realize that no, no, that muskie smell, that is the
(22:09):
smell of the seals. So it smells very similar to
skunk in my opinion.
Speaker 1 (22:14):
What do they sound like? Is it loud like you
hear like a thousand seals going off.
Speaker 3 (22:20):
During the day, Typically not at all unless they're they're
kind of bickering and fighting and having some territorial little battles.
At night time, it's sort of a consistent, low bellowing
that you hear in the background while you're while you're
trying to sleep. It's actually quite nice ambient noise.
Speaker 1 (22:44):
It does sound a feeling that sounds better than the
smell certainly right. So so you're out there, what do
you do?
Speaker 3 (22:52):
We are going out and actually capturing the pups, and
we focus on the pups because they are, give take,
about one hundred pounds as opposed to the adults, which
can be around eight hundred pounds. So we're able to
physically restrain the pups. And that's why we're there during
January and February because that's the pupping season. It can
be somewhat comical if you didn't know what was going on.
(23:14):
You've got a bunch of scientists all geared up, and
we are crawling through army crawl style through the dunes
to sneak up on a seal pup and put this
bag over the seal that we then capture it, and
we're doing sample collections. We're doing measurements to look for
just the overall health of the animals, and then we
(23:37):
put a tag on them. In some cases we put
on a satellite tag so we can actually follow their
movement and then we release them and all of that
can happen and as quickly as six minutes, and then
we max it out at twenty minutes. So if we
hit twenty minutes, we release the seal.
Speaker 1 (23:54):
So when you go out in the winter and you
are swabbing baby seals, like you are doing the sentinel work,
you're like out there looking for H five in one
to be the early warning system for the rest of us. Exactly.
Speaker 3 (24:09):
We are trying to pick up anything that might be
developing the ability to go from birds to mammals and
then trying to figure out is that something that then
presents the possibility that it could then come into humans
or other wild mammals, but mammals in general.
Speaker 1 (24:26):
So if I hope not, When let's say, if someone
finds a clear instance of H five in one spreading
from mammal to mammal, what will that mean?
Speaker 3 (24:41):
That is the point where we collectively need to get
much more serious about preparing for it. The good news
with high path influenza is I like to say, it's
not COVID, so it's we see it coming. We know influenza,
we have vaccines against influenza. We have seed stocks that
(25:02):
are maintained to be able to rapidly grow up vaccines,
so we have the capacity to respond. It's important that
we continue to do very robust surveillance so that we
know if or when these changes happen, and what exactly
they look like.
Speaker 1 (25:18):
I will say, after talking to you about what's happening
with H five N one and mammals, I'm certainly not
not worried, but I am less worried than I was
before I talk to you.
Speaker 3 (25:31):
Excellent. I like to think that we will be prepared
for the human health side of things, that we will
be prepared to respond pretty efficiently and pretty rapidly should
it become a concern for human health. My bigger concern
is for wildlife. That's a much trickier one for us
to be able to mitigate, and it could have a
(25:54):
very long lasting, very negative impact to several wildlife species.
But I think from human health we will be able
to hopefully respond well.
Speaker 1 (26:04):
I appreciate all your time.
Speaker 3 (26:05):
Yeah, absolutely.
Speaker 1 (26:08):
One last thing. About a month after we spoke with Wendy,
H five N one was detected in seals off the
coast of Washington State. It was the first time AGE
five and one had been detected in marine mammals off
the west coast of the United States. Thanks to my
guest today, David Quarman and Wendy per Year. Next week
(26:29):
we'll be talking about HPV human peppellomavirus and about how
the HPV vaccine explains American's complicated relationship to all vaccines.
Speaker 3 (26:41):
The HPV story is so interesting because support was coming
from everywhere, but backlash was coming from everywhere too, Like
all over the Political Spectrum.
Speaker 1 (26:51):
Incubation is a co production of Pushkin Industries and Ruby
Studio at iHeartMedia. It's produced by Gabriel Hunter Chang, Ariela Markowitz,
and am Gaines McQuaid. Our editors are Julia Barton and
Karen Schakerjie Mastering by Anne Pope, fact checking by Joseph Friedman.
Our executive producers are Katherine Girardeau and Matt Romano. I'm
(27:12):
Jacob Goldstein. Thanks for listening.
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