November 14, 2023 • 35 mins
Ever wondered how bird flu affects not just our feathered friends, but also the wider ecosystem? Prepare to be enlightened as we journey into the world of avian influenza with Dr. Greg Gray. A respected authority on respiratory pathogens and one health, Dr. Gray offers invaluable insights into this widespread pandemic, highlighting the different hemagglutinin and neuraminidase types and their impact on various species. He also spotlights the longest and most severe outbreak of avian influenza in recent history. But remember, this is more than a bird issue, it’s a stark reminder of the intricate interconnectivity of life on Earth, including humans, animals, plants, and the environment.
Delving further, Dr. Gray unearths the complexities of species barriers and how they can be bypassed. He highlights the role of salicylic acid on human cells and shares intriguing discussions on the occupational exposure to live bird markets, virus particle sizes and the potential of bird flu becoming more transmissible. Our exploration also extends to the realm of virology, with a fascinating look at how viruses exchange genetic information. A highlight of this chat is the potential of swine being ideal mixing vessels for viruses. So, whether you’re a health enthusiast, a bird lover or just plain curious, this episode is for you! Don't miss out on this comprehensive understanding of avian influenza and its broader implications for one health.
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Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 2 (00:09):
This is a podcast about one health the idea that
the health of humans, animals,plants and the environment that
we all share are intrinsicallylinked.
Speaker 1 (00:17):
Coming to you from the University of Texas Medical
Branch in the Galveston NationalLaboratory.
Speaker 2 (00:21):
This is infectious science.
We're enthusiasm for science.
Speaker 1 (00:25):
It's contagious.
Hey everyone, thanks for tuningin.
This is Danielle.
Speaker 2 (00:34):
Hey Danielle, how are you?
Speaker 1 (00:36):
Good, this is Matt this is Matt Dashow.
And we're also here with Dennis.
Speaker 3 (00:40):
I almost thought you could forget me here.
Speaker 2 (00:43):
You are all the way across the room.
Speaker 1 (00:44):
Yes, so this past year there's been reports all
over the news of mass birddiopsis associated with
influenza.
Speaker 2 (00:51):
Yeah, I remember I was traveling in Peru earlier in
the year and I was with anepidemiology colleague and we
were taking a walk on the beachand on the beach there must have
been dozens of dead seabirdsand it was kind of a startling
thing to see.
And then he told me about therehad been some hundreds of sea
lions that had washed up in Peruas well.
Oh gosh, yeah, that also hadbeen affected by bird flu.
(01:13):
So this seems to be a prettysignificant pandemic of bird flu
across the world.
Speaker 1 (01:17):
Yeah, and you might have noticed the huge increase
in the price of eggs and chickenin the grocery store kind of
earlier this year.
It was pretty devastating.
Speaker 2 (01:26):
We are egg fanatics in my family and so, yes, we
felt it in our pocketbook.
Speaker 3 (01:30):
Yeah, so if you're on a ketogenic diet, you know
you're probably noticed.
Speaker 1 (01:35):
So to help us talk a little bit more about the
biology of avian influenza andgenerally issues in one health,
we invited an expert to comespeak with us, Dr Greg Gray.
He's a professor here at UTMBand he's also one of the leading
experts we have on respiratorypathogens in one health.
So thanks for coming.
Speaker 4 (01:56):
Thanks for inviting me, daniel and Matt and Dennis
Pleasure to be here.
Speaker 2 (01:59):
Yeah, we are so happy to have you here.
This is a One Health podcastand we are actually getting to
speak with a One Health expert.
Speaker 3 (02:07):
Yeah, this is a long overdue right.
Speaker 1 (02:09):
Yeah, yeah.
So let's jump into some of themeat and potatoes.
Really, what is avian influenzaand how is that different from
human influenza?
Speaker 4 (02:18):
Well, there are many different strains of influenza
and it's the influenza A groupthat causes the avian types and
so there's four types influenzaA, b, c and D.
That's correct, and it's theinfluenza A's that troubles us,
both in the human and animalkingdoms, the most.
(02:39):
And getting back to yourquestion, the influenza A's
there's some 18 differenthemaclutinin types and some 11
different neuraminidase types,and the vast majority of those
types can infect birds.
Speaker 1 (02:53):
So when you say that you're talking about like the
H1N1, H5N1, those naming kind ofthings that we all hear, when
that's correct.
Speaker 2 (03:02):
Those are identifiers that help you differentiate the
different subtypes, right Likethere are certain proteins that
are on the virus itself.
Speaker 4 (03:09):
Yeah, they're considered glycoproteins and
they've long been followed andas the most important antigenic
components of the virus.
What are immune systems see andtheir ability to attach and
evade cells?
Or what defines disease indifferent animal species?
Speaker 1 (03:25):
Right.
So these are the proteins thatare on the surface of the virus,
right?
And that they're the primaryproteins involved in cell entry.
So they're really what isdefining not only what species
is being infected, but whattissues within that species is
being infected, so if it's theirlungs or their upper
respiratory tract or theirintestines or something like
that, right.
Speaker 4 (03:45):
Yeah, that's correct, Danielle.
Yeah, okay, good.
Speaker 1 (03:48):
I remember virology 101.
It's good.
Speaker 2 (03:52):
You've surpassed my knowledge.
Now I'm learning now.
Speaker 1 (03:56):
Sometimes we have to review these things because I
don't always remember my basicvirology.
Speaker 2 (04:01):
So, greg, I was talking about this a little
earlier with kind of the birdswere on the beach, the sea lions
were washing up.
We've heard about certainly inthe news, there's all of this
news about some other animalslike minks up in some of the
Scandinavian countries comingdown with bird flu, and so it
seems like the avian influenzacan infect all kinds of
(04:21):
different species.
Can you say a little bit aboutthat and how that works?
Speaker 4 (04:24):
Yeah, we're continuing to learn new species
that are susceptible, if youwill, to infection, and there
have been a tremendous number ofoutbreaks among avian species
here in the last 10 years.
The World Organization forAnimal Health has documented
some 21,000 outbreaks in recentyears, oh geez.
And because so many animalshave died, carnivores in
(04:47):
particular have been eatingthose scarcasses and we've
suddenly seen strange carnivoresmanifesting serious illness and
dying from an ingesting birdsthat died from avian flu, and
then they too, including thingslike grizzly bears, which is
totally unknown, and so we'reseeing outbreaks and carnivores
(05:08):
and outbreaks and other domesticanimals.
It's been quite interesting.
Speaker 2 (05:11):
I wanted to ask you, greg, is this?
I mean, what I've been readingis that this is maybe among the
worst and longest outbreaks ofavian influenza in the world.
Is that the case?
Speaker 4 (05:22):
Yeah, of course our diagnostics and ability to
characterize viruses haveincreased over time, but
certainly in the last 20 to 30years this seems to be the
largest.
In fact, the virologists haveindicated that for the various
different strains of virus,there are at least 34 different
avian influenza subtypes thathave caused these outbreaks,
which is astounding, and a lotof these are particularly H5 and
(05:45):
they're in zootically sayinganimals through many parts of
the world and it's got a lot ofpeople very concerned that if
they should develop increasedmorbidity characteristics or
ability to spill over to humans,we could be in trouble.
Speaker 1 (05:59):
So this is one of the things that really gets me is,
I think when we name things orwhen we colloquially refer to
things as avian flu or swine flu, it kind of gives us this
really misleading sense ofsecurity.
This isn't really a bird flu.
This is just a bird adapted flu.
It doesn't take a big jump forit to adapt to something else.
(06:20):
Right, Evolution is constantlyhappening.
So I think the naming, the waywe talk about these things is
misleading a little bit, right.
Speaker 3 (06:27):
Yeah, I think that's a very good point and I think
it's very easy for the public toalso then think if it's called
avian flu, then you all of asudden turn into a bird or
something like that when you getinfected.
I know that's memes that comeout, but I think the naming is a
very good point, danielle.
Speaker 1 (06:43):
And I think sometimes it's even had really
devastating consequences wherethere might be an outbreak of
swine flu.
So people just start cullingpigs around the world, or
they'll start culling birdsaround the world, because we
have this idea that this virusis circulating and even if
there's no exposure, in order tokeep ourselves safe in an era
of fear, we kind of don't alwaysbehave in an intelligent way.
Speaker 2 (07:05):
I wanted to nerd out real quick with a question for
you, Greg.
We know that there are somedifferences between, let's say
this, avian flu and then humaninfluenza.
Are those different viruses?
Are they different?
Hs and Ns?
How do they differ?
Speaker 4 (07:18):
Well, yeah, so I mentioned earlier that there's
some 18 different hemagglutininsand 11 different neuraminidases
, and 16 of those 18 affectbirds, and about nine of the
neuraminidases affect birds, andso birds harbor almost all the
permutations of those 16 by 11variants, and some of them are
(07:39):
really innocuous in the birds,quite well tolerated.
Some of them cause severedisease, particularly the H5 and
the H7 variants, and we'rebasically susceptible as humans
to a number of these, but inparticular the highly pathogenic
H5 and H7s in the birds havecaused the most severe illness
in humans.
Speaker 1 (07:59):
Okay, so correct me if I'm wrong, but avian
influenza has a pretty hard timeinfecting humans, am I right?
Speaker 4 (08:07):
Yeah, I think that's been demonstrated quite clearly
just by the numbers of avianspecies that have been infected
in a close contact with humansand the really sparse number of
humans that have manifestedclinical signs and symptoms.
Of course there's always thesuggestion and serologic studies
have borne this out that thereare subclinical infections going
(08:28):
on that we're missing.
But it's true there's a hugespecies barrier between avian
species infected with flu andthat moving over to spill over
to humans.
Speaker 1 (08:36):
I think it's kind of really interesting to me about
how this happens.
So from my understanding,there's really two types of
salicylic acid on the surface ofcells, which is where influenza
is binding to, and in humans inthe lower respiratory tract.
So, like your lungs, we haveboth, but in your upper
respiratory tract you only haveone.
And human influenza viruses arereally well adapted at
(08:59):
infecting and binding to cellsthat are in your upper
respiratory tract and then fromthere they can spread to your
lungs and that's where you'rereally going to get a lot of the
significant disease.
But avian influenza viruses oravian adapted influenza viruses
aren't really able to readilyinfect the cells in your upper
respiratory tract, so that's whythey have a hard time
(09:20):
establishing infection.
But if they are able to getdown into your lungs, that's
where they're able to infect andestablish an infection, and
that's why you have these reallysevere outcomes of people that
are infected with an avianinfluenza but they're not able
to transmit it because theirupper respiratory tract isn't
involved, so like their nose andthroat, and that's where you're
breathing in, exhaling virus oryou're breathing it in.
(09:41):
So that has more to do with thetransmissibility.
Speaker 4 (09:44):
I've read, that is, that yeah, I think that's
accurate, very accurate.
It's the occupational exposureswhere there's intense
aerosolization of viralparticles.
Speaker 1 (09:53):
When you say occupational, what are you
talking about?
Speaker 4 (09:55):
Well, people that work in live bird markets all
day, especially live birdmarkets where there are inzotic
many different strains of liveavian flu.
It just makes sense that thosepeople have a tolerance from the
chronic insults to their immunesystem with those antigens and
people that are totallyimmunological and naive or at
risk when they go into thoseenvironments.
Speaker 3 (10:16):
And I think what we've learned from COVID is the
particle size also matters,right, if a droplet is formed
and it's a fairly large dropletthrough sneezing or something
like that, it doesn't travelvery far in the environment and
it also doesn't travel very farin our respiratory tracts, right
.
But if the particle size isvery small, then it travels
deeper into our lungs.
(10:37):
So the way something isaerosolized also matters in that
regard.
Interesting, interesting.
Speaker 4 (10:43):
That's exactly right, and I'll just say that we've
done some bio-aerosol samplingin very large bird markets One
bird market near Hanoi, vietnam.
Almost half the aerosamples hadmolecular evidence of avian flu
and some of those were viablein this system which isn't
really that great at capturing alive virus and preserving it,
(11:04):
and so some of these settingsare naturally aerosolizing virus
and feather and dust particlesand it's no wonder that one of
the exposures that people havewho develop avian flu is
contacting those live birdmarkets.
Often one of the exposuresRight.
Speaker 2 (11:21):
I think the only case that I saw, that at least we've
seen in the US, was a poultryfarmer in Colorado.
Is that correct?
I think there's only been maybeone or just a couple.
Speaker 4 (11:30):
Yeah, there have not been many here that I know of in
recent years.
Speaker 1 (11:33):
But the fear is that I would be able to become more
transmissible.
Speaker 4 (11:37):
Yes, If it were to develop the capacity to move
from human to humans.
We're in trouble.
Just look at all the detectionsof these H5 strains here in the
United States.
If you look at the USDA's mapof those in wild birds or even
in the domestic flocks, thoseare virus that quite widespread
in their distributions.
Speaker 3 (11:57):
I want to intersect right there and just ask a
question.
I think for us as scientistsand risk communication, like you
just mentioned, greg, if thisadapts more to humans, we're in
trouble.
So, as virologists, we have thetask to educate the public, but
often the public will perceivethis as fear mongering.
At the same time, we have theduty to educate them.
(12:19):
How do you think, in terms ofscience communication and risk
communication, we should informthe public.
Speaker 4 (12:25):
Well, dennis, I think the best measure is not to hide
truth from the public.
We've been shown time and timeagain that doesn't work, and so
a realistic measurement of riskis prudent.
And right now the speciesbarrier between avian flu as
infecting avian species andtransferred to humans is very
high, and that has to do withour host immunity, that has to
(12:49):
do with the receptivity of thevirus, and so I'm not as alarmed
with the threats of avian fluas I am with some of the other
flu viruses.
Speaker 1 (12:57):
I think that the thing that is unique about avian
flu, though, is how fast it canspread.
Just because we are living avery global economy, people are
moving all over the place, butbirds themselves are migrating
without the assistance of humans, so even if we were to
quarantine or stop movement, thevirus would still presumably
(13:18):
circulate on its own.
Is that that's correct?
Speaker 4 (13:21):
Yeah, it's pretty amazing If you chat with the
wildlife biologists who monitoravian species.
The thousands of miles some ofthese species travel and how
they form up before they dotheir migrations in areas that
other species form up, how theymix during those migrations,
basically accelerate the crossspecies transmissions in the
(13:42):
avian populations.
And I've heard it expressed asthese birds are dropping many
bomblets of fecal material overvast geographical areas and
that's particularly what makesour poultry farms threatened.
It's very easy to move thevirus through the migrating
birds and if your biosecurityand your poultry farm lets that
virus be introduced by onemeasure or another, your farm
(14:05):
can have an explosion in avianinfluenza viral infections.
Speaker 1 (14:09):
So wait a minute.
How is it spread among birds?
It's a GI virus, yeah, yeah,because when I think of flu, I
think of respiratory pathogens,but it's only a respiratory
pathogen in us yeah, the oralfecal is thought to be the
primary method of transmissionin birds.
Speaker 4 (14:24):
Humans can actually acquire the infection through
multiple different ways directcontact, aerosolization, as we
mentioned, and possibly oralingestion, and until recently we
didn't give much credence tothe aerosolization threat.
But I think SARS-CV-2 hasreally got us concerned now,
because we certainly know thatvirus moves quite readily in the
(14:46):
air, as Dennis said, in smallparticles.
Speaker 2 (14:49):
Yeah, I was going to ask.
As you were talking, I wasenvisioning these things that
happen naturally as birds arepreparing to migrate and they
cluster and they're around otheranimals.
What about on poultry farms?
What about where there isindustrial poultry farming?
What do they do if they have anoutbreak or how do they detect
it?
Speaker 4 (15:06):
I think we have some of the most biosecure poultry,
beef and pork farms in the worldand they follow very strict
biosecurity procedures to reduce, we say, barn-to-barn
transmission on a farm andparticularly to reduce
farm-to-farm transmission.
And so there are a lot ofdifferent measures that people
(15:27):
use rodent control, becauserodents can physically carry it,
passerine birds control, accesswith screening, the wearing of
personal protective gear inhumans, filtration in some cases
of some of the airs, the feedin the water not having any
contaminants.
So there's a lot of things thatcan be done and are done to
(15:48):
protect poultry farms.
But these tricky viruses, theyoften have a way to circumvent
things.
And when that does, you see anexplosive outbreak and the
farmer must report this to theagricultural experts, usda and
AFIS.
And then there's a mass cullingeffort to remove the threat to
other farms with somecompensation, although many
(16:10):
would argue it's not enough.
Speaker 1 (16:11):
Right, and I'm sure that's country-specific right
and like region-specific.
Well, that's the United States,the story is quite different
than other countries.
Speaker 4 (16:18):
Yeah, the biosecurity is in some cases not very good
and the mitigation strategiesmay not be as well rehearsed and
the reporting requirementsperhaps less enforced.
I came from Duke not long agoand I got to know some of the
folks.
They had something like 200volunteers to respond to an
avian flu outbreak.
(16:39):
They had a whole lot full offoaming gear and everything.
It looked like an army reservecenter of equipment that they
would move to the farm and killthe birds rapidly and dispose of
them in a safe way so that noother birds would be infected or
no other carnivores would eatthe carcasses.
Speaker 1 (16:57):
Yeah, that's neat.
Speaker 2 (16:58):
Wow, it's just gotta be so devastating and difficult.
Do you think of it from apublic health standpoint as?
Oh well, of course, you justhave to cull the flock.
But wow, if you're a farmer andthis is your livelihood and
you're depending on theproductivity of these animals
and you care for them, this hasgotta be just devastating.
Speaker 3 (17:14):
I just had a quick question, since you brought up
the efforts to contain the virusand so on.
There are many differentinfluenza networks around the
world that try to predict andalso stop the spread of
different influenza strains.
We know the migratory birdroutes of birds.
Is there a targeted approach tohave sentinels in certain areas
(17:34):
on these migratory routes?
Speaker 1 (17:36):
Can I jump in?
Speaker 3 (17:37):
Yes.
Speaker 1 (17:38):
We do not know.
This is my pet peeve.
We do not know the migratorypatterns of birds.
We have oversimplified themigratory patterns of birds to
make them convenient.
They're more likeadministrative migratory
patterns of birds.
Sorry, this was a big point ofcontention during my
dissertation and it's one of mypet peeves about the way we kind
(17:58):
of make birds fly at certaintimes of years and under these
very narrow corridors which onlyreally are reflecting a very
narrow species.
But bird migration isinfinitely more dynamic than
these little maps that wecirculate.
Speaker 3 (18:12):
That's true.
At the same time, though,there's certain bottlenecks that
birds have to go through right.
Speaker 1 (18:17):
Yes, I absolutely agree.
Speaker 4 (18:19):
I mean we're seeing flamingos here on the island
that shouldn't be here.
So you're right.
But getting back to Dennis'sexcellent question, there are
concerted efforts and they'vewaxed and waned over the years,
many of these for surveillancein birds, for viruses.
Many of these have been led bythe Centers of Excellence in
influenza sponsored by the NIAID, and particularly St Jude's
(18:42):
Center of Excellence.
They've been sampling ducks onthe East Coast, migrating birds,
shorebirds, for a long time,but people probably would argue
that it's not enough and they'vereduced that migrating bird
surveillance, with exceptionwhen they're die-offs in recent
years?
Speaker 3 (18:59):
This is actually a question for Matt.
So now where your primary carephysician hat your internal
medicine hat, do you think youwould recognize a human with
avian influenza infection?
Speaker 2 (19:10):
That is a great question.
In the process of trying tomake a diagnosis for a
particular disease, there aremany times where we don't even
send confirmatory diagnostictests.
We treat empirically because weknow what the epidemiology is
right and it's only if someonefails to improve or are
manifesting other uniquesymptoms that we might start to
(19:33):
trigger other types of workups.
And I would answer thatquestion differently, probably
five years ago, before reallystarting to work with folks like
yourselves and One Health,where now my history taking in
the clinical encounter is muchmore broad, to where someone
especially manifesting symptomsof infectious disease.
I'm asking about a lot moreanimal exposures, not just
(19:55):
travel, but, you know, farm,environmental exposures.
So I think maybe the astuteclinician might think about it.
But especially if it'ssomething we're not a customer
seeing, we might miss it and wemight not even know where to go
for the diagnostic testing Imean.
So it's, you know, rapid flutest.
I can send it and I have aresult within minutes, right?
Speaker 1 (20:13):
Would a rapid flu test distinguish?
Speaker 2 (20:15):
No not.
Speaker 4 (20:16):
Usually you would just know that you've got
influenza A.
So you wouldn't really know ifit's avian flu, influenza A,
yeah, and particularly youwouldn't know unless there's a
lot of concern that it would beswine flu, because the
hemagglutinin types of human andswine are very similar H1s and
H3s and there's a subset ofinfluenza A.
(20:37):
Positive specimens are studiedto detect novel viruses.
But I think Dr Daschau wascorrect in that the sensitivity
of picking them up, who knows?
Speaker 2 (20:49):
Yeah, it's probably pretty low and you'd have to
request sequencing.
Speaker 4 (20:53):
Yeah, I mean, if you had a severe disease, you're
definitely going to work it up,but if it's just a mild disease
and seems to resolve on its own,you know why spend all that
time when he's studying itExactly.
So, I think that's why a lot ofthese zoonotic influenza A's
that we think are happening byserologic data are being missed
in the clinics.
Speaker 2 (21:14):
That's so interesting .
I was going to ask a question.
Actually, kind of coming backto something, greg, you
mentioned animals eating thecarcasses of birds that have
died or other animals that havepassed from this, and that that
could be sort of a route fortransmission.
What about eating the meat oreggs of infected birds that come
from poultry farms that mayhave had an outbreak?
Is there a risk for humans orif it's cooked, it's okay?
Speaker 4 (21:35):
Well, there's a risk that humans might be infected by
touching raw meat from poultry,and it's not just influenza A,
but many different, as you know,other organisms, including
bacterial strains.
In general, though, if youhandle the meat or the eggs with
a modicum of care, they're verysafe to eat, and especially if
(21:56):
you cook everything thoroughly.
So I'm not so worried aboutthat, although there have been
some incidental reports tosuggest that it's a possible
mechanism, but that doesn'tconcern most influenza experts.
Speaker 2 (22:08):
So the message cook your eggs, cook your meat Right.
Speaker 1 (22:11):
And wash your hands.
Speaker 2 (22:12):
The big jug of raw eggs and protein powder that
you're taking, Dennis, for yourwork out every day, Every day.
You know you got to cook thoseeggs.
Speaker 3 (22:20):
Yes, I think it's good to know that the measures
that we're taking to preventcampylobactyl salmonella
whatever chicken meat can bringuncooked right that those
measures are good enough to killoff influenza as well.
Speaker 4 (22:33):
Yeah, one could argue that the influenza viruses are
less hardy than many of thebacterial pathogens that are
potentially in our animal foodproducts.
Speaker 2 (22:42):
Greg, one of the things that I've been following
in the news.
There was an article talkingabout mink farms in some
Scandinavian countries, minksthat were becoming infected with
COVID, essentially withSARS-CoV-2.
And these minks are alsosusceptible both to avian
influenza and to human influenzaviruses and they can in fact be
co-infected at the same time.
And so there's these ideas thatmaybe there are certain species
(23:06):
that can host multiple virusestogether, and is there potential
for those to co-mingle, toexchange DNA fragments.
Can you walk us through that?
Is that sort of sci-fi or isthat?
Speaker 4 (23:17):
No, that's a reality and it's been well documented
for many years, the potentialfor the mixing of these viruses.
There are three primary waysthe viruses can mix.
One is basically through thesharing of large assortments
segments, if you will, largesegments of the virus.
When two or more viruses gointo a cell and they start
(23:38):
producing progeny viruses, youget sometimes a child virus, if
you will.
That's a mixture of the twoviruses and that reassortment
can cause major changes.
Fortunately, when it happens,most of the time it doesn't
cause illness.
It becomes non-functional.
Another way is to share onlypart of the segments through
something called recombination,and that frequently occurs.
(24:00):
And then the final way is justthrough mutation.
As the virus replicates, itsometimes makes mistakes and you
get a unique virus throughthose measures.
But influenza viruses and otherRNA viruses are really prone to
making mistakes throughmutations and through changing
through recombination.
Speaker 1 (24:18):
Kind of the way I think about this, there's two
buzzwords.
There's anagenic drift andshift.
Drift, which is the slowaccumulation of mutations, and
then there's shift, which is thebig reassortments that we were
just talking about.
We all know I'm a geek forevolution, so excuse me while I
geek out for a minute, but Ilove this analogy.
When we're talking about thatkind of slow accumulation of
(24:38):
mutations, I always think of itas a game of molecular telephone
where first you have I'm sayingMatt, and then the next person
hears cat and then the nextperson hears mad.
The virus basically makesmistakes every time it
replicates and these kind ofincremental little changes is
like the mechanism of these hugeevolutionary features and
phenomenon that we observe innature all the time, and it can
(25:01):
be really powerful.
And influenza, and I thinkthere's only like a couple of
mutations that are required forsome of these big host jumps
that we see.
Speaker 3 (25:10):
So the way I explain reassortment to my students in
the virology course is alwayslike imagine you have two decks
of cards right the same decks ofcards and one is maybe a red
deck and the other one is a bluedeck.
And then you take some of thecards from each deck and you
throw them into a bucket or somesort of vessel and if the
(25:31):
number and the time is right andyou reach into that vessel and
you pull the cards out, youmight have a full deck, but it's
a mixture of the red deck andthe blue deck.
So you have a new mixed deckbut it's still possible to play
with.
It's just has very differentcomponents.
Speaker 1 (25:48):
But it's a lot more challenging to happen, right?
Because not only does oneperson have to be infected with
two different viruses, a singlecell has to be infected with two
different viruses.
So I think that's what makespeople concerned about birds as
being a possible mixing vesselwhere you can have multiple
viruses mixing within a bird.
(26:08):
But I know you are a big fan ofthe hypothesis that swine are a
better mixing vessel.
Speaker 4 (26:16):
Well, yeah, I think humans can be a mixing vessel.
True, true, true but swine seemto have the ability to be
infected with larger numbers ofvery influenza viruses, and so
they've often been given themoniker of a mixing vessel.
I think there are a number ofthings about pigs, if we want to
talk about pig influenzaviruses that are in Zootiekin
(26:36):
pigs.
In contrast to poultry, whichmay live a couple months, the
shortest live pigs or productionpigs are six months, and so
there's a longer time period forthem to be infected with lots
of different viruses, andthey're in contact with a number
of different species, often inthe developing world anyway,
humans, as I mentioned,passerine birds, sometimes dogs
(26:57):
and cats, sometimes ducks andgeese are pinned right next to
them.
So there's a tremendousopportunity and their
susceptibility to these variedinfluenza viruses for mixing to
go on the pigs, and often it'sbeen said that it's the pigs
that have been implicated in anumber of influenza A pandemics.
Speaker 1 (27:17):
So is it that you think pigs are a better mixing
vessel, or pig adapted virusesare more likely to spill over?
Speaker 4 (27:25):
Well, I think pig-adapted viruses are both, I
guess, are more likely to spillover to humans.
We are closer to pigs and ourevolution and we are, I would
argue, to a lot of avian species.
We even share tissues.
Even today in modern medicine,transplanting, yeah, and so
(27:45):
there's organs beingtransplanted.
So we have a capability to beinfected with those viruses and
the serial epidemiologic studieswe've done indicate, in very
high prevalence pig herds thatthe workers almost cannot escape
being infected with the virusesin the swine that are being
amplified if they work withthose pigs.
(28:07):
So it's like more than 90%infection rate if you're
susceptible at the beginning ofthe time period you're following
Interesting.
So that's why I say that thespecies barriers pig to humans
is much lower than the speciesbarrier or avian species to
humans?
Speaker 3 (28:26):
I think that's Matt's question.
It's just really, reallyinteresting and maybe, if you
allow me, greg, maybe we canphilosophize about this question
.
And it's in his philosophyquestion, yeah, so I think our
society always has thisperception of spillovers as like
a black or white event, right?
So, danielle, you've worked alot with West Nile this theory
that a couple from Israeltraveled to the US with a bird
(28:48):
and that was the one time thatall of a sudden, west Nile was
introduced into the WesternHemisphere and spread like a
wildfire and I think we alwayshave these stories that this is
a single event.
It jumped the species barrierand all of a sudden it just
takes off like a wildfire.
And I always question that.
And, based on what you say, itsounds like there's always these
(29:10):
attempts of spillover andsometimes it occurs, but then
it's stopped at some point.
Sometimes it doesn't even occurin the first place.
Sometimes it goes a little bitfurther and then maybe the
infection will die out after awhile.
What are your thoughts on thesespillover events?
Do you think those are reallysingle, like we like to portray
them in our society, as blackand white events, or are these
(29:32):
like waves of crashing onto thebeach and then at some point,
the conditions are right and wehave a tsunami?
Speaker 4 (29:40):
Yeah, Well, dennis, I agree with your metaphor of
crashing on the beach, because Ithink when humans are exposed
to large populations of animals,whether it be for meat
production or wildlife orlibrary markets, there's a great
propensity for those animalscarrying viruses to challenge
the immune system, and thesuccess of those challenges.
(30:03):
To take a foothold in a newspecies has got to be extremely
rare.
And for it to continue to adaptonce it has begun to take a
foothold, in other words, thevirus has adapted in the host.
It didn't really causehuman-to-human transmission, but
it continues to insult otherhumans, that takes a long time
too.
And then, finally, when you seelimited transmission, the
(30:24):
probability of that is evenrarer.
And then efficient transmissionand viral evolutions would say
the odds of these eventshappening are extremely low, and
the time involved, based onmutations that are seen in the
phylogenetic structure ofsimilar viruses, would suggest
that we have time to detectthese insulting viruses that are
(30:47):
beginning to get a foothold, ifwe only know how to look for
them.
And the problem is we don'tknow how to look for them Among
people that have clinicaldisease very well, because our
diagnostics are very tuned infor known pathogens, and so
that's been a matter of debate.
I was just on a World HealthOrganization call for a group of
virus called adenoviruses andmaybe I should be careful here
(31:09):
because I'm not a disclosureagreement.
But the bottom line is the mostthreatening viruses are those
that we can't detect in the listof all the adenoviruses.
And what does that say?
That means you better come upwith some better way to
diagnosis in the clinics, orit'll take an epidemic to get
you to do so.
Speaker 2 (31:25):
Yeah, and I find health care in general to be
pretty reactionary as far as newtechnologies and development of
these sort of things.
We had a new disease, so wedeveloped diagnostics for it and
then it's always there.
It's always sort of at thedownstream, and as clinicians
that's sort of where we live,and so we don't always look
upstream and start to think well, how do we create something
(31:47):
that is a bit less specific andsomething that would actually
serve a different purpose?
That would be part of earlydetection or surveillance.
Speaker 4 (31:54):
And we're actually trying to do that here, and
we've done that in a number ofour epidemiologic studies, and
I'm pleased to say that we'vehad a modicum of success
detecting viruses and speciesthat shouldn't have been there,
including a very unusualdog-like canine coronavirus, we
call it that was found first ineastern Malaysia and then later
(32:14):
in Haiti, and so we have arguedthat, particularly for
coronaviruses and influenzaviruses, they're probably
spilling over a lot more thansome of the other viruses and we
need to have these pan-speciesdiagnostics up and running for
them.
Speaker 3 (32:28):
Before I let you go, greg, I have one more question
as a concerned citizen livinghere in Galveston.
Galveston is well known forbirders around the world.
People come.
We have migratory birdsstopping here on the way to
South America, so I have a birdfeeder in my backyard and I know
friends that have chicken coop.
(32:48):
So what is your advice?
Do you think that's risky?
Or what do you think?
Take them down, or just keep aneye on them?
Or what are your thoughts?
Speaker 4 (32:58):
I don't know that bird feeders have been
implicated.
It has a risk factor for avianflu to go to humans.
I've never seen that so Iwouldn't worry about that.
We have seen concerns thatbackyard flocks, so to speak,
that are exposed to migratingbirds because they're not in a
pen or covered in a barn mightbe more prone to acquiring avian
(33:19):
flu and there's been a bigeducational program by the USDA
for those people that keep thebackyard flocks.
But in general if a flu goes inthere it burns right through
that population.
It's a small population.
It's never going to besustained.
In contrast, when you have10,000 chickens and multiple
barns you get an avian flu inthere.
That doesn't kill the birds.
(33:40):
It has a great opportunity tobecome inzutically, say, and of
course that's a concern.
In this country if they findany avian flu they call the
birds.
But in other countries you havemultiple strains that are
inzutic in the poultry and thatcan be a setup for the mixing we
talked about earlier.
Speaker 2 (33:55):
I learned a ton today .
I learned about thetransmission dynamics.
I learned about risk, I learnedabout what is this virus and
how is it characterized.
Wow, we, really we covered alot of ground.
Speaker 1 (34:05):
Thank you so much for making time to talk to us.
Speaker 4 (34:07):
Well, thank you, it's been a pleasure and fun
chatting with you guys.
Speaker 1 (34:09):
Thanks for listening to the Infectious Science
podcast.
Be sure to hit Subscribe andvisit infectiousscienceorg to
join the conversation, accessthe show notes and to sign up
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Speaker 2 (34:20):
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Speaker 1 (34:29):
Also, don't hesitate to ask questions and tell us
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To get in touch, drop a line inthe comments section or send us
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Speaker 2 (34:38):
So we'll see you next time for a new episode, and in
the meantime, stay happy stayhealthy, stay interested.
This is a podcast about one health the idea that
the health of humans, animals,plants and the environment that
we all share are intrinsicallylinked.
Speaker 1 (00:17):
Coming to you from the University of Texas Medical
Branch in the Galveston NationalLaboratory.
Speaker 2 (00:21):
This is infectious science.
We're enthusiasm for science.
Speaker 1 (00:25):
It's contagious.
Hey everyone, thanks for tuningin.
This is Danielle.
Speaker 2 (00:34):
Hey Danielle, how are you?
Speaker 1 (00:36):
Good, this is Matt this is Matt Dashow.
And we're also here with Dennis.
Speaker 3 (00:40):
I almost thought you could forget me here.
Speaker 2 (00:43):
You are all the way across the room.
Speaker 1 (00:44):
Yes, so this past year there's been reports all
over the news of mass birddiopsis associated with
influenza.
Speaker 2 (00:51):
Yeah, I remember I was traveling in Peru earlier in
the year and I was with anepidemiology colleague and we
were taking a walk on the beachand on the beach there must have
been dozens of dead seabirdsand it was kind of a startling
thing to see.
And then he told me about therehad been some hundreds of sea
lions that had washed up in Peruas well.
Oh gosh, yeah, that also hadbeen affected by bird flu.
(01:13):
So this seems to be a prettysignificant pandemic of bird flu
across the world.
Speaker 1 (01:17):
Yeah, and you might have noticed the huge increase
in the price of eggs and chickenin the grocery store kind of
earlier this year.
It was pretty devastating.
Speaker 2 (01:26):
We are egg fanatics in my family and so, yes, we
felt it in our pocketbook.
Speaker 3 (01:30):
Yeah, so if you're on a ketogenic diet, you know
you're probably noticed.
Speaker 1 (01:35):
So to help us talk a little bit more about the
biology of avian influenza andgenerally issues in one health,
we invited an expert to comespeak with us, Dr Greg Gray.
He's a professor here at UTMBand he's also one of the leading
experts we have on respiratorypathogens in one health.
So thanks for coming.
Speaker 4 (01:56):
Thanks for inviting me, daniel and Matt and Dennis
Pleasure to be here.
Speaker 2 (01:59):
Yeah, we are so happy to have you here.
This is a One Health podcastand we are actually getting to
speak with a One Health expert.
Speaker 3 (02:07):
Yeah, this is a long overdue right.
Speaker 1 (02:09):
Yeah, yeah.
So let's jump into some of themeat and potatoes.
Really, what is avian influenzaand how is that different from
human influenza?
Speaker 4 (02:18):
Well, there are many different strains of influenza
and it's the influenza A groupthat causes the avian types and
so there's four types influenzaA, b, c and D.
That's correct, and it's theinfluenza A's that troubles us,
both in the human and animalkingdoms, the most.
(02:39):
And getting back to yourquestion, the influenza A's
there's some 18 differenthemaclutinin types and some 11
different neuraminidase types,and the vast majority of those
types can infect birds.
Speaker 1 (02:53):
So when you say that you're talking about like the
H1N1, H5N1, those naming kind ofthings that we all hear, when
that's correct.
Speaker 2 (03:02):
Those are identifiers that help you differentiate the
different subtypes, right Likethere are certain proteins that
are on the virus itself.
Speaker 4 (03:09):
Yeah, they're considered glycoproteins and
they've long been followed andas the most important antigenic
components of the virus.
What are immune systems see andtheir ability to attach and
evade cells?
Or what defines disease indifferent animal species?
Speaker 1 (03:25):
Right.
So these are the proteins thatare on the surface of the virus,
right?
And that they're the primaryproteins involved in cell entry.
So they're really what isdefining not only what species
is being infected, but whattissues within that species is
being infected, so if it's theirlungs or their upper
respiratory tract or theirintestines or something like
that, right.
Speaker 4 (03:45):
Yeah, that's correct, Danielle.
Yeah, okay, good.
Speaker 1 (03:48):
I remember virology 101.
It's good.
Speaker 2 (03:52):
You've surpassed my knowledge.
Now I'm learning now.
Speaker 1 (03:56):
Sometimes we have to review these things because I
don't always remember my basicvirology.
Speaker 2 (04:01):
So, greg, I was talking about this a little
earlier with kind of the birdswere on the beach, the sea lions
were washing up.
We've heard about certainly inthe news, there's all of this
news about some other animalslike minks up in some of the
Scandinavian countries comingdown with bird flu, and so it
seems like the avian influenzacan infect all kinds of
(04:21):
different species.
Can you say a little bit aboutthat and how that works?
Speaker 4 (04:24):
Yeah, we're continuing to learn new species
that are susceptible, if youwill, to infection, and there
have been a tremendous number ofoutbreaks among avian species
here in the last 10 years.
The World Organization forAnimal Health has documented
some 21,000 outbreaks in recentyears, oh geez.
And because so many animalshave died, carnivores in
(04:47):
particular have been eatingthose scarcasses and we've
suddenly seen strange carnivoresmanifesting serious illness and
dying from an ingesting birdsthat died from avian flu, and
then they too, including thingslike grizzly bears, which is
totally unknown, and so we'reseeing outbreaks and carnivores
(05:08):
and outbreaks and other domesticanimals.
It's been quite interesting.
Speaker 2 (05:11):
I wanted to ask you, greg, is this?
I mean, what I've been readingis that this is maybe among the
worst and longest outbreaks ofavian influenza in the world.
Is that the case?
Speaker 4 (05:22):
Yeah, of course our diagnostics and ability to
characterize viruses haveincreased over time, but
certainly in the last 20 to 30years this seems to be the
largest.
In fact, the virologists haveindicated that for the various
different strains of virus,there are at least 34 different
avian influenza subtypes thathave caused these outbreaks,
which is astounding, and a lotof these are particularly H5 and
(05:45):
they're in zootically sayinganimals through many parts of
the world and it's got a lot ofpeople very concerned that if
they should develop increasedmorbidity characteristics or
ability to spill over to humans,we could be in trouble.
Speaker 1 (05:59):
So this is one of the things that really gets me is,
I think when we name things orwhen we colloquially refer to
things as avian flu or swine flu, it kind of gives us this
really misleading sense ofsecurity.
This isn't really a bird flu.
This is just a bird adapted flu.
It doesn't take a big jump forit to adapt to something else.
(06:20):
Right, Evolution is constantlyhappening.
So I think the naming, the waywe talk about these things is
misleading a little bit, right.
Speaker 3 (06:27):
Yeah, I think that's a very good point and I think
it's very easy for the public toalso then think if it's called
avian flu, then you all of asudden turn into a bird or
something like that when you getinfected.
I know that's memes that comeout, but I think the naming is a
very good point, danielle.
Speaker 1 (06:43):
And I think sometimes it's even had really
devastating consequences wherethere might be an outbreak of
swine flu.
So people just start cullingpigs around the world, or
they'll start culling birdsaround the world, because we
have this idea that this virusis circulating and even if
there's no exposure, in order tokeep ourselves safe in an era
of fear, we kind of don't alwaysbehave in an intelligent way.
Speaker 2 (07:05):
I wanted to nerd out real quick with a question for
you, Greg.
We know that there are somedifferences between, let's say
this, avian flu and then humaninfluenza.
Are those different viruses?
Are they different?
Hs and Ns?
How do they differ?
Speaker 4 (07:18):
Well, yeah, so I mentioned earlier that there's
some 18 different hemagglutininsand 11 different neuraminidases
, and 16 of those 18 affectbirds, and about nine of the
neuraminidases affect birds, andso birds harbor almost all the
permutations of those 16 by 11variants, and some of them are
(07:39):
really innocuous in the birds,quite well tolerated.
Some of them cause severedisease, particularly the H5 and
the H7 variants, and we'rebasically susceptible as humans
to a number of these, but inparticular the highly pathogenic
H5 and H7s in the birds havecaused the most severe illness
in humans.
Speaker 1 (07:59):
Okay, so correct me if I'm wrong, but avian
influenza has a pretty hard timeinfecting humans, am I right?
Speaker 4 (08:07):
Yeah, I think that's been demonstrated quite clearly
just by the numbers of avianspecies that have been infected
in a close contact with humansand the really sparse number of
humans that have manifestedclinical signs and symptoms.
Of course there's always thesuggestion and serologic studies
have borne this out that thereare subclinical infections going
(08:28):
on that we're missing.
But it's true there's a hugespecies barrier between avian
species infected with flu andthat moving over to spill over
to humans.
Speaker 1 (08:36):
I think it's kind of really interesting to me about
how this happens.
So from my understanding,there's really two types of
salicylic acid on the surface ofcells, which is where influenza
is binding to, and in humans inthe lower respiratory tract.
So, like your lungs, we haveboth, but in your upper
respiratory tract you only haveone.
And human influenza viruses arereally well adapted at
(08:59):
infecting and binding to cellsthat are in your upper
respiratory tract and then fromthere they can spread to your
lungs and that's where you'rereally going to get a lot of the
significant disease.
But avian influenza viruses oravian adapted influenza viruses
aren't really able to readilyinfect the cells in your upper
respiratory tract, so that's whythey have a hard time
(09:20):
establishing infection.
But if they are able to getdown into your lungs, that's
where they're able to infect andestablish an infection, and
that's why you have these reallysevere outcomes of people that
are infected with an avianinfluenza but they're not able
to transmit it because theirupper respiratory tract isn't
involved, so like their nose andthroat, and that's where you're
breathing in, exhaling virus oryou're breathing it in.
(09:41):
So that has more to do with thetransmissibility.
Speaker 4 (09:44):
I've read, that is, that yeah, I think that's
accurate, very accurate.
It's the occupational exposureswhere there's intense
aerosolization of viralparticles.
Speaker 1 (09:53):
When you say occupational, what are you
talking about?
Speaker 4 (09:55):
Well, people that work in live bird markets all
day, especially live birdmarkets where there are inzotic
many different strains of liveavian flu.
It just makes sense that thosepeople have a tolerance from the
chronic insults to their immunesystem with those antigens and
people that are totallyimmunological and naive or at
risk when they go into thoseenvironments.
Speaker 3 (10:16):
And I think what we've learned from COVID is the
particle size also matters,right, if a droplet is formed
and it's a fairly large dropletthrough sneezing or something
like that, it doesn't travelvery far in the environment and
it also doesn't travel very farin our respiratory tracts, right
.
But if the particle size isvery small, then it travels
deeper into our lungs.
(10:37):
So the way something isaerosolized also matters in that
regard.
Interesting, interesting.
Speaker 4 (10:43):
That's exactly right, and I'll just say that we've
done some bio-aerosol samplingin very large bird markets One
bird market near Hanoi, vietnam.
Almost half the aerosamples hadmolecular evidence of avian flu
and some of those were viablein this system which isn't
really that great at capturing alive virus and preserving it,
(11:04):
and so some of these settingsare naturally aerosolizing virus
and feather and dust particlesand it's no wonder that one of
the exposures that people havewho develop avian flu is
contacting those live birdmarkets.
Often one of the exposuresRight.
Speaker 2 (11:21):
I think the only case that I saw, that at least we've
seen in the US, was a poultryfarmer in Colorado.
Is that correct?
I think there's only been maybeone or just a couple.
Speaker 4 (11:30):
Yeah, there have not been many here that I know of in
recent years.
Speaker 1 (11:33):
But the fear is that I would be able to become more
transmissible.
Speaker 4 (11:37):
Yes, If it were to develop the capacity to move
from human to humans.
We're in trouble.
Just look at all the detectionsof these H5 strains here in the
United States.
If you look at the USDA's mapof those in wild birds or even
in the domestic flocks, thoseare virus that quite widespread
in their distributions.
Speaker 3 (11:57):
I want to intersect right there and just ask a
question.
I think for us as scientistsand risk communication, like you
just mentioned, greg, if thisadapts more to humans, we're in
trouble.
So, as virologists, we have thetask to educate the public, but
often the public will perceivethis as fear mongering.
At the same time, we have theduty to educate them.
(12:19):
How do you think, in terms ofscience communication and risk
communication, we should informthe public.
Speaker 4 (12:25):
Well, dennis, I think the best measure is not to hide
truth from the public.
We've been shown time and timeagain that doesn't work, and so
a realistic measurement of riskis prudent.
And right now the speciesbarrier between avian flu as
infecting avian species andtransferred to humans is very
high, and that has to do withour host immunity, that has to
(12:49):
do with the receptivity of thevirus, and so I'm not as alarmed
with the threats of avian fluas I am with some of the other
flu viruses.
Speaker 1 (12:57):
I think that the thing that is unique about avian
flu, though, is how fast it canspread.
Just because we are living avery global economy, people are
moving all over the place, butbirds themselves are migrating
without the assistance of humans, so even if we were to
quarantine or stop movement, thevirus would still presumably
(13:18):
circulate on its own.
Is that that's correct?
Speaker 4 (13:21):
Yeah, it's pretty amazing If you chat with the
wildlife biologists who monitoravian species.
The thousands of miles some ofthese species travel and how
they form up before they dotheir migrations in areas that
other species form up, how theymix during those migrations,
basically accelerate the crossspecies transmissions in the
(13:42):
avian populations.
And I've heard it expressed asthese birds are dropping many
bomblets of fecal material overvast geographical areas and
that's particularly what makesour poultry farms threatened.
It's very easy to move thevirus through the migrating
birds and if your biosecurityand your poultry farm lets that
virus be introduced by onemeasure or another, your farm
(14:05):
can have an explosion in avianinfluenza viral infections.
Speaker 1 (14:09):
So wait a minute.
How is it spread among birds?
It's a GI virus, yeah, yeah,because when I think of flu, I
think of respiratory pathogens,but it's only a respiratory
pathogen in us yeah, the oralfecal is thought to be the
primary method of transmissionin birds.
Speaker 4 (14:24):
Humans can actually acquire the infection through
multiple different ways directcontact, aerosolization, as we
mentioned, and possibly oralingestion, and until recently we
didn't give much credence tothe aerosolization threat.
But I think SARS-CV-2 hasreally got us concerned now,
because we certainly know thatvirus moves quite readily in the
(14:46):
air, as Dennis said, in smallparticles.
Speaker 2 (14:49):
Yeah, I was going to ask.
As you were talking, I wasenvisioning these things that
happen naturally as birds arepreparing to migrate and they
cluster and they're around otheranimals.
What about on poultry farms?
What about where there isindustrial poultry farming?
What do they do if they have anoutbreak or how do they detect
it?
Speaker 4 (15:06):
I think we have some of the most biosecure poultry,
beef and pork farms in the worldand they follow very strict
biosecurity procedures to reduce, we say, barn-to-barn
transmission on a farm andparticularly to reduce
farm-to-farm transmission.
And so there are a lot ofdifferent measures that people
(15:27):
use rodent control, becauserodents can physically carry it,
passerine birds control, accesswith screening, the wearing of
personal protective gear inhumans, filtration in some cases
of some of the airs, the feedin the water not having any
contaminants.
So there's a lot of things thatcan be done and are done to
(15:48):
protect poultry farms.
But these tricky viruses, theyoften have a way to circumvent
things.
And when that does, you see anexplosive outbreak and the
farmer must report this to theagricultural experts, usda and
AFIS.
And then there's a mass cullingeffort to remove the threat to
other farms with somecompensation, although many
(16:10):
would argue it's not enough.
Speaker 1 (16:11):
Right, and I'm sure that's country-specific right
and like region-specific.
Well, that's the United States,the story is quite different
than other countries.
Speaker 4 (16:18):
Yeah, the biosecurity is in some cases not very good
and the mitigation strategiesmay not be as well rehearsed and
the reporting requirementsperhaps less enforced.
I came from Duke not long agoand I got to know some of the
folks.
They had something like 200volunteers to respond to an
avian flu outbreak.
(16:39):
They had a whole lot full offoaming gear and everything.
It looked like an army reservecenter of equipment that they
would move to the farm and killthe birds rapidly and dispose of
them in a safe way so that noother birds would be infected or
no other carnivores would eatthe carcasses.
Speaker 1 (16:57):
Yeah, that's neat.
Speaker 2 (16:58):
Wow, it's just gotta be so devastating and difficult.
Do you think of it from apublic health standpoint as?
Oh well, of course, you justhave to cull the flock.
But wow, if you're a farmer andthis is your livelihood and
you're depending on theproductivity of these animals
and you care for them, this hasgotta be just devastating.
Speaker 3 (17:14):
I just had a quick question, since you brought up
the efforts to contain the virusand so on.
There are many differentinfluenza networks around the
world that try to predict andalso stop the spread of
different influenza strains.
We know the migratory birdroutes of birds.
Is there a targeted approach tohave sentinels in certain areas
(17:34):
on these migratory routes?
Speaker 1 (17:36):
Can I jump in?
Speaker 3 (17:37):
Yes.
Speaker 1 (17:38):
We do not know.
This is my pet peeve.
We do not know the migratorypatterns of birds.
We have oversimplified themigratory patterns of birds to
make them convenient.
They're more likeadministrative migratory
patterns of birds.
Sorry, this was a big point ofcontention during my
dissertation and it's one of mypet peeves about the way we kind
(17:58):
of make birds fly at certaintimes of years and under these
very narrow corridors which onlyreally are reflecting a very
narrow species.
But bird migration isinfinitely more dynamic than
these little maps that wecirculate.
Speaker 3 (18:12):
That's true.
At the same time, though,there's certain bottlenecks that
birds have to go through right.
Speaker 1 (18:17):
Yes, I absolutely agree.
Speaker 4 (18:19):
I mean we're seeing flamingos here on the island
that shouldn't be here.
So you're right.
But getting back to Dennis'sexcellent question, there are
concerted efforts and they'vewaxed and waned over the years,
many of these for surveillancein birds, for viruses.
Many of these have been led bythe Centers of Excellence in
influenza sponsored by the NIAID, and particularly St Jude's
(18:42):
Center of Excellence.
They've been sampling ducks onthe East Coast, migrating birds,
shorebirds, for a long time,but people probably would argue
that it's not enough and they'vereduced that migrating bird
surveillance, with exceptionwhen they're die-offs in recent
years?
Speaker 3 (18:59):
This is actually a question for Matt.
So now where your primary carephysician hat your internal
medicine hat, do you think youwould recognize a human with
avian influenza infection?
Speaker 2 (19:10):
That is a great question.
In the process of trying tomake a diagnosis for a
particular disease, there aremany times where we don't even
send confirmatory diagnostictests.
We treat empirically because weknow what the epidemiology is
right and it's only if someonefails to improve or are
manifesting other uniquesymptoms that we might start to
(19:33):
trigger other types of workups.
And I would answer thatquestion differently, probably
five years ago, before reallystarting to work with folks like
yourselves and One Health,where now my history taking in
the clinical encounter is muchmore broad, to where someone
especially manifesting symptomsof infectious disease.
I'm asking about a lot moreanimal exposures, not just
(19:55):
travel, but, you know, farm,environmental exposures.
So I think maybe the astuteclinician might think about it.
But especially if it'ssomething we're not a customer
seeing, we might miss it and wemight not even know where to go
for the diagnostic testing Imean.
So it's, you know, rapid flutest.
I can send it and I have aresult within minutes, right?
Speaker 1 (20:13):
Would a rapid flu test distinguish?
Speaker 2 (20:15):
No not.
Speaker 4 (20:16):
Usually you would just know that you've got
influenza A.
So you wouldn't really know ifit's avian flu, influenza A,
yeah, and particularly youwouldn't know unless there's a
lot of concern that it would beswine flu, because the
hemagglutinin types of human andswine are very similar H1s and
H3s and there's a subset ofinfluenza A.
(20:37):
Positive specimens are studiedto detect novel viruses.
But I think Dr Daschau wascorrect in that the sensitivity
of picking them up, who knows?
Speaker 2 (20:49):
Yeah, it's probably pretty low and you'd have to
request sequencing.
Speaker 4 (20:53):
Yeah, I mean, if you had a severe disease, you're
definitely going to work it up,but if it's just a mild disease
and seems to resolve on its own,you know why spend all that
time when he's studying itExactly.
So, I think that's why a lot ofthese zoonotic influenza A's
that we think are happening byserologic data are being missed
in the clinics.
Speaker 2 (21:14):
That's so interesting .
I was going to ask a question.
Actually, kind of coming backto something, greg, you
mentioned animals eating thecarcasses of birds that have
died or other animals that havepassed from this, and that that
could be sort of a route fortransmission.
What about eating the meat oreggs of infected birds that come
from poultry farms that mayhave had an outbreak?
Is there a risk for humans orif it's cooked, it's okay?
Speaker 4 (21:35):
Well, there's a risk that humans might be infected by
touching raw meat from poultry,and it's not just influenza A,
but many different, as you know,other organisms, including
bacterial strains.
In general, though, if youhandle the meat or the eggs with
a modicum of care, they're verysafe to eat, and especially if
(21:56):
you cook everything thoroughly.
So I'm not so worried aboutthat, although there have been
some incidental reports tosuggest that it's a possible
mechanism, but that doesn'tconcern most influenza experts.
Speaker 2 (22:08):
So the message cook your eggs, cook your meat Right.
Speaker 1 (22:11):
And wash your hands.
Speaker 2 (22:12):
The big jug of raw eggs and protein powder that
you're taking, Dennis, for yourwork out every day, Every day.
You know you got to cook thoseeggs.
Speaker 3 (22:20):
Yes, I think it's good to know that the measures
that we're taking to preventcampylobactyl salmonella
whatever chicken meat can bringuncooked right that those
measures are good enough to killoff influenza as well.
Speaker 4 (22:33):
Yeah, one could argue that the influenza viruses are
less hardy than many of thebacterial pathogens that are
potentially in our animal foodproducts.
Speaker 2 (22:42):
Greg, one of the things that I've been following
in the news.
There was an article talkingabout mink farms in some
Scandinavian countries, minksthat were becoming infected with
COVID, essentially withSARS-CoV-2.
And these minks are alsosusceptible both to avian
influenza and to human influenzaviruses and they can in fact be
co-infected at the same time.
And so there's these ideas thatmaybe there are certain species
(23:06):
that can host multiple virusestogether, and is there potential
for those to co-mingle, toexchange DNA fragments.
Can you walk us through that?
Is that sort of sci-fi or isthat?
Speaker 4 (23:17):
No, that's a reality and it's been well documented
for many years, the potentialfor the mixing of these viruses.
There are three primary waysthe viruses can mix.
One is basically through thesharing of large assortments
segments, if you will, largesegments of the virus.
When two or more viruses gointo a cell and they start
(23:38):
producing progeny viruses, youget sometimes a child virus, if
you will.
That's a mixture of the twoviruses and that reassortment
can cause major changes.
Fortunately, when it happens,most of the time it doesn't
cause illness.
It becomes non-functional.
Another way is to share onlypart of the segments through
something called recombination,and that frequently occurs.
(24:00):
And then the final way is justthrough mutation.
As the virus replicates, itsometimes makes mistakes and you
get a unique virus throughthose measures.
But influenza viruses and otherRNA viruses are really prone to
making mistakes throughmutations and through changing
through recombination.
Speaker 1 (24:18):
Kind of the way I think about this, there's two
buzzwords.
There's anagenic drift andshift.
Drift, which is the slowaccumulation of mutations, and
then there's shift, which is thebig reassortments that we were
just talking about.
We all know I'm a geek forevolution, so excuse me while I
geek out for a minute, but Ilove this analogy.
When we're talking about thatkind of slow accumulation of
(24:38):
mutations, I always think of itas a game of molecular telephone
where first you have I'm sayingMatt, and then the next person
hears cat and then the nextperson hears mad.
The virus basically makesmistakes every time it
replicates and these kind ofincremental little changes is
like the mechanism of these hugeevolutionary features and
phenomenon that we observe innature all the time, and it can
(25:01):
be really powerful.
And influenza, and I thinkthere's only like a couple of
mutations that are required forsome of these big host jumps
that we see.
Speaker 3 (25:10):
So the way I explain reassortment to my students in
the virology course is alwayslike imagine you have two decks
of cards right the same decks ofcards and one is maybe a red
deck and the other one is a bluedeck.
And then you take some of thecards from each deck and you
throw them into a bucket or somesort of vessel and if the
(25:31):
number and the time is right andyou reach into that vessel and
you pull the cards out, youmight have a full deck, but it's
a mixture of the red deck andthe blue deck.
So you have a new mixed deckbut it's still possible to play
with.
It's just has very differentcomponents.
Speaker 1 (25:48):
But it's a lot more challenging to happen, right?
Because not only does oneperson have to be infected with
two different viruses, a singlecell has to be infected with two
different viruses.
So I think that's what makespeople concerned about birds as
being a possible mixing vesselwhere you can have multiple
viruses mixing within a bird.
(26:08):
But I know you are a big fan ofthe hypothesis that swine are a
better mixing vessel.
Speaker 4 (26:16):
Well, yeah, I think humans can be a mixing vessel.
True, true, true but swine seemto have the ability to be
infected with larger numbers ofvery influenza viruses, and so
they've often been given themoniker of a mixing vessel.
I think there are a number ofthings about pigs, if we want to
talk about pig influenzaviruses that are in Zootiekin
(26:36):
pigs.
In contrast to poultry, whichmay live a couple months, the
shortest live pigs or productionpigs are six months, and so
there's a longer time period forthem to be infected with lots
of different viruses, andthey're in contact with a number
of different species, often inthe developing world anyway,
humans, as I mentioned,passerine birds, sometimes dogs
(26:57):
and cats, sometimes ducks andgeese are pinned right next to
them.
So there's a tremendousopportunity and their
susceptibility to these variedinfluenza viruses for mixing to
go on the pigs, and often it'sbeen said that it's the pigs
that have been implicated in anumber of influenza A pandemics.
Speaker 1 (27:17):
So is it that you think pigs are a better mixing
vessel, or pig adapted virusesare more likely to spill over?
Speaker 4 (27:25):
Well, I think pig-adapted viruses are both, I
guess, are more likely to spillover to humans.
We are closer to pigs and ourevolution and we are, I would
argue, to a lot of avian species.
We even share tissues.
Even today in modern medicine,transplanting, yeah, and so
(27:45):
there's organs beingtransplanted.
So we have a capability to beinfected with those viruses and
the serial epidemiologic studieswe've done indicate, in very
high prevalence pig herds thatthe workers almost cannot escape
being infected with the virusesin the swine that are being
amplified if they work withthose pigs.
(28:07):
So it's like more than 90%infection rate if you're
susceptible at the beginning ofthe time period you're following
Interesting.
So that's why I say that thespecies barriers pig to humans
is much lower than the speciesbarrier or avian species to
humans?
Speaker 3 (28:26):
I think that's Matt's question.
It's just really, reallyinteresting and maybe, if you
allow me, greg, maybe we canphilosophize about this question
.
And it's in his philosophyquestion, yeah, so I think our
society always has thisperception of spillovers as like
a black or white event, right?
So, danielle, you've worked alot with West Nile this theory
that a couple from Israeltraveled to the US with a bird
(28:48):
and that was the one time thatall of a sudden, west Nile was
introduced into the WesternHemisphere and spread like a
wildfire and I think we alwayshave these stories that this is
a single event.
It jumped the species barrierand all of a sudden it just
takes off like a wildfire.
And I always question that.
And, based on what you say, itsounds like there's always these
(29:10):
attempts of spillover andsometimes it occurs, but then
it's stopped at some point.
Sometimes it doesn't even occurin the first place.
Sometimes it goes a little bitfurther and then maybe the
infection will die out after awhile.
What are your thoughts on thesespillover events?
Do you think those are reallysingle, like we like to portray
them in our society, as blackand white events, or are these
(29:32):
like waves of crashing onto thebeach and then at some point,
the conditions are right and wehave a tsunami?
Speaker 4 (29:40):
Yeah, Well, dennis, I agree with your metaphor of
crashing on the beach, because Ithink when humans are exposed
to large populations of animals,whether it be for meat
production or wildlife orlibrary markets, there's a great
propensity for those animalscarrying viruses to challenge
the immune system, and thesuccess of those challenges.
(30:03):
To take a foothold in a newspecies has got to be extremely
rare.
And for it to continue to adaptonce it has begun to take a
foothold, in other words, thevirus has adapted in the host.
It didn't really causehuman-to-human transmission, but
it continues to insult otherhumans, that takes a long time
too.
And then, finally, when you seelimited transmission, the
(30:24):
probability of that is evenrarer.
And then efficient transmissionand viral evolutions would say
the odds of these eventshappening are extremely low, and
the time involved, based onmutations that are seen in the
phylogenetic structure ofsimilar viruses, would suggest
that we have time to detectthese insulting viruses that are
(30:47):
beginning to get a foothold, ifwe only know how to look for
them.
And the problem is we don'tknow how to look for them Among
people that have clinicaldisease very well, because our
diagnostics are very tuned infor known pathogens, and so
that's been a matter of debate.
I was just on a World HealthOrganization call for a group of
virus called adenoviruses andmaybe I should be careful here
(31:09):
because I'm not a disclosureagreement.
But the bottom line is the mostthreatening viruses are those
that we can't detect in the listof all the adenoviruses.
And what does that say?
That means you better come upwith some better way to
diagnosis in the clinics, orit'll take an epidemic to get
you to do so.
Speaker 2 (31:25):
Yeah, and I find health care in general to be
pretty reactionary as far as newtechnologies and development of
these sort of things.
We had a new disease, so wedeveloped diagnostics for it and
then it's always there.
It's always sort of at thedownstream, and as clinicians
that's sort of where we live,and so we don't always look
upstream and start to think well, how do we create something
(31:47):
that is a bit less specific andsomething that would actually
serve a different purpose?
That would be part of earlydetection or surveillance.
Speaker 4 (31:54):
And we're actually trying to do that here, and
we've done that in a number ofour epidemiologic studies, and
I'm pleased to say that we'vehad a modicum of success
detecting viruses and speciesthat shouldn't have been there,
including a very unusualdog-like canine coronavirus, we
call it that was found first ineastern Malaysia and then later
(32:14):
in Haiti, and so we have arguedthat, particularly for
coronaviruses and influenzaviruses, they're probably
spilling over a lot more thansome of the other viruses and we
need to have these pan-speciesdiagnostics up and running for
them.
Speaker 3 (32:28):
Before I let you go, greg, I have one more question
as a concerned citizen livinghere in Galveston.
Galveston is well known forbirders around the world.
People come.
We have migratory birdsstopping here on the way to
South America, so I have a birdfeeder in my backyard and I know
friends that have chicken coop.
(32:48):
So what is your advice?
Do you think that's risky?
Or what do you think?
Take them down, or just keep aneye on them?
Or what are your thoughts?
Speaker 4 (32:58):
I don't know that bird feeders have been
implicated.
It has a risk factor for avianflu to go to humans.
I've never seen that so Iwouldn't worry about that.
We have seen concerns thatbackyard flocks, so to speak,
that are exposed to migratingbirds because they're not in a
pen or covered in a barn mightbe more prone to acquiring avian
(33:19):
flu and there's been a bigeducational program by the USDA
for those people that keep thebackyard flocks.
But in general if a flu goes inthere it burns right through
that population.
It's a small population.
It's never going to besustained.
In contrast, when you have10,000 chickens and multiple
barns you get an avian flu inthere.
That doesn't kill the birds.
(33:40):
It has a great opportunity tobecome inzutically, say, and of
course that's a concern.
In this country if they findany avian flu they call the
birds.
But in other countries you havemultiple strains that are
inzutic in the poultry and thatcan be a setup for the mixing we
talked about earlier.
Speaker 2 (33:55):
I learned a ton today .
I learned about thetransmission dynamics.
I learned about risk, I learnedabout what is this virus and
how is it characterized.
Wow, we, really we covered alot of ground.
Speaker 1 (34:05):
Thank you so much for making time to talk to us.
Speaker 4 (34:07):
Well, thank you, it's been a pleasure and fun
chatting with you guys.
Speaker 1 (34:09):
Thanks for listening to the Infectious Science
podcast.
Be sure to hit Subscribe andvisit infectiousscienceorg to
join the conversation, accessthe show notes and to sign up
for our newsletter and receiveour free materials.
Speaker 2 (34:20):
If you enjoyed this new episode of Infectious
Science, please leave us areview on Apple Podcasts at
Spotify and go ahead and sharethis episode with some of your
friends.
Speaker 1 (34:29):
Also, don't hesitate to ask questions and tell us
what topics you'd like us tocover for future episodes.
To get in touch, drop a line inthe comments section or send us
a message on social media.
Speaker 2 (34:38):
So we'll see you next time for a new episode, and in
the meantime, stay happy stayhealthy, stay interested.
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