Speaker 1: My name is Reagan, and I grew up in a
Speaker 1: very small town. I had exactly seventeen people in my
Speaker 1: high school graduation, so I just wanted to set the
Speaker 1: stage of what I was dealing with in the medical community.
Speaker 1: When I was sixteen, my school was getting ready for
Speaker 1: homecoming and we were the last class they got to
Speaker 1: have a bonfire at ours, so we really wanted to
Speaker 1: go all out for everyone, not just for us. And
Speaker 1: I really wasn't big on the outdoors. I wasn't an
Speaker 1: outside fan. I didn't like wearing the long sleeves, the pants,
Speaker 1: the mosquito's fright. But I worked hard for this and
Speaker 1: it was an amazing bonfire. It was actually only a
Speaker 1: few days later that I was spending and linking with
Speaker 1: my grandmother, and right after school I came down with
Speaker 1: a headache and I wasn't interested in watching TV. I
Speaker 1: wasn't interested in eating dinner. I even went to bed
Speaker 1: before the sunset. And my grandmother was really increasing worried
Speaker 1: over this behavior. She was checking on me every half hour.
Speaker 1: She wanted to take me to the er, but she knew,
Speaker 1: especially in time my cars, that they were just going
Speaker 1: to send me home with tile at all. So then
Speaker 1: the fever hit, and when it hit, it came on
Speaker 1: hard and fast, and my grandmother called the hospital, who
Speaker 1: said that all they would do was put me in
Speaker 1: an icepath and send me home. That was their fever protocol.
Speaker 1: So she called my mom, who was a five hour
Speaker 1: dRIT away, and all I remember her saying is something
Speaker 1: isn't right. I think you need to come home. She'd
Speaker 1: been gone for school, she'd been with a friend. She
Speaker 1: didn't even have her own car, but something in my
Speaker 1: grandmother's voice convinced her, so she rented it something. She
Speaker 1: came home, and by the time that the fever got
Speaker 1: so bad that she was having to lay on me
Speaker 1: to keep the chills from shaking the bed, she decided
Speaker 1: she was done. We were going to the er. I
Speaker 1: don't really remember much from them now it gets really hazy.
Speaker 1: I remember being super uncomfortable. I remember begging my mom
Speaker 1: to go home. I just wanted my bed. I wanted
Speaker 1: to sleep. The doctors were asking me to do all
Speaker 1: these things that I couldn't do. I couldn't stand up,
Speaker 1: I couldn't stay conscious, and they were asking me to
Speaker 1: touch my chin to my chest and I couldn't do
Speaker 1: it it hurts so bad. And that's when things started
Speaker 1: to get scary. I didn't know until later that they
Speaker 1: told my family that I was going to die. And
Speaker 1: I was like in the room, like laying on the bed,
Speaker 1: and my mother demanded that i'd be moved to the
Speaker 1: hospital that was in the bigger city. It was an
Speaker 1: hour away, and they said that I wouldn't make it.
Speaker 1: And then there was one doctor who came into the
Speaker 1: room said he was giving me an ambulance and that
Speaker 1: he would have a friend waiting for my arrival because
Speaker 1: he was very scared that this was something very serious.
Speaker 1: Everything after that kind of comes in flashes. I remember
Speaker 1: the night sky becoming the roof of an ambulance. I
Speaker 1: remember my mother's face while she stroked my hair. I
Speaker 1: remember being pulled away from her so they could do
Speaker 1: a spinal tap, which was the scariest thing that's ever
Speaker 1: happened to me in my entire life. I remember too
Speaker 1: many hands on me while they moved me to a stretcher.
Speaker 1: I remember my father arriving, which was like a big
Speaker 1: deal of My dad actually came to a hospital, and
Speaker 1: I remembered my pediatrician because I had been so healthy
Speaker 1: up into my teen years that I hadn't actually acquired
Speaker 1: a GP yet. I remember hazard suits because I didn't
Speaker 1: actually know if what I had was bacterial or viral.
Speaker 1: I was so dehydrated that they blew my vein trying
Speaker 1: to give me IVS. I was still maninurish that I
Speaker 1: lost fifteen pounds in the hospital. I was so weak
Speaker 1: that I had to relearn how to walk, and I
Speaker 1: remember thinking that I was going to die, and I
Speaker 1: was okay with that, and it was actually well before
Speaker 1: the results came in West nilmanuingitis. I missed two weeks
Speaker 1: of school between treatment and recovery. It took even longer
Speaker 1: to return to normal, and my classmates had to help
Speaker 1: me carry things between classes because the locks were too
Speaker 1: long and my body was too exhausted. And I remember
Speaker 1: my teacher was giving me gift baskets and extensions on
Speaker 1: my homework, and my family members made me homemade cine
Speaker 1: mem roles. He gave my weight back, And it didn't
Speaker 1: occur to me until much later that everyone was doing
Speaker 1: this because I wasn't supposed to make it. Everyone had
Speaker 1: said that I was going to die. Preparations had been
Speaker 1: made at the school for me to not come back,
Speaker 1: and because I did, nobody wanted to let me research
Speaker 1: what had almost killed me. They waited patiently for my
Speaker 1: obsession with it to disappear, and it did until I
Speaker 1: started listening to your podcasts.
Speaker 2: That's well, thank you so much, Reagan for taking the
Speaker 2: time to tell your story.
Speaker 3: Wow, I mean what a story.
Speaker 2: Yeah, thank you, it's absolutely terrifying.
Speaker 4: Yeah, seriously. Yeah.
Speaker 2: Well, Hi, I'm Erin Welsh.
Speaker 4: And I'm Erin Allman Updyke and this is this podcast
Speaker 4: will kill you. Welcome to West Now Virus. Welcome to
Speaker 4: West Style Virus.
Speaker 2: And what is our second to last episode of this season?
Speaker 4: I really truly can't believe that we've made it this far. Erin,
Speaker 4: I'm going to be completely honest.
Speaker 2: I mean same and yeah, so we are after the
Speaker 2: end of this season, so not this episode, but the
Speaker 2: one after will be the last of the season.
Speaker 4: We're going to be taking a short break.
Speaker 2: Don't worry, we won't be gone forever.
Speaker 4: We'll be back. We'll be back.
Speaker 2: So you know, make sure that you're subscribed to the
Speaker 2: podcast to all of our social media so you know
Speaker 2: what we're doing in the break and also when we're
Speaker 2: coming out with a new episode.
Speaker 4: Yeah, or any other fun surprises that could happen. Who knows.
Speaker 4: We don't know. Anything could happen. Anything could happen.
Speaker 2: But yeah, West Nile, Aaron, this is our first mosquito
Speaker 2: born one of this season.
Speaker 3: Is that right?
Speaker 5: Is it?
Speaker 4: I guess it is. I'm going to be totally honest
Speaker 4: this season, I don't even remember what things we've done.
Speaker 4: I know we did shagus, so I know that was
Speaker 4: a vector Boyne disease.
Speaker 2: I'm just also surprised that we hadn't done West Nile yet, Like,
Speaker 2: this is a this is kind of a big deal.
Speaker 4: Oh, Aaron, you could just play a broken record of
Speaker 4: us in our intros saying the exact same thing for
Speaker 4: every single episode.
Speaker 6: It is.
Speaker 3: It is true.
Speaker 7: Oh man, It's gonna be a good episode though.
Speaker 2: It is for a number of reasons. So you just
Speaker 2: heard that incredible first hand account. And we have another
Speaker 2: fantastic guest lined up for this episode to help shed
Speaker 2: some light on the ecology of West Nile virus. And
Speaker 2: one of the most exciting things you have to stay
Speaker 2: tuned for the very very end of the episode, and
Speaker 2: that's because there is a West Nile rap al rap
Speaker 2: It is called West Nile Story and it is by
Speaker 2: friend of the podcast mc bugsy, who made it in
Speaker 2: collaboration with the Fairfax County Health Department working in the
Speaker 2: Disease Carrying Insects program Fairfax County, Virginia.
Speaker 3: I had to look that up.
Speaker 4: I am so excited for everyone to hear it.
Speaker 3: Oh my gosh.
Speaker 2: So it is absolutely a fantastic song. And not only that,
Speaker 2: like this is not mc bugsy's only song, So make
Speaker 2: sure you go to YouTube. We'll provide a link, don't worry,
Speaker 2: and you can check out all of the raps. There's
Speaker 2: even one about COVID vaccines.
Speaker 4: It is incredible, awesome. Well and speaking of classic TPWKY,
Speaker 4: it's about time for quarantiney.
Speaker 2: It is what are we drinking this week?
Speaker 4: We're drinking for the birds.
Speaker 2: Which, like we want to make sure that you know,
Speaker 2: it's for the opposite of the reason that people.
Speaker 3: Usually say for the birds.
Speaker 2: We wanted to name it this to honor the birds.
Speaker 4: It's for the bird.
Speaker 3: It is for the birds. This is for the birds.
Speaker 2: Can we say it?
Speaker 4: What is in for the birds?
Speaker 2: Erin so for the birds is actually based on an
Speaker 2: existing cocktail also named after a bird called the yellow
Speaker 2: Bird cocktail.
Speaker 4: Very apt, very apt it is.
Speaker 2: And that is made with white rum, orange liqueur galiano
Speaker 2: and lime juice.
Speaker 4: Delish.
Speaker 3: It is tart and delish.
Speaker 4: We'll post a full recipe for that quarantini as well
Speaker 4: as our non alcoholic plasy Bereta on our website This
Speaker 4: Podcast will kill You dot Com and all of our
Speaker 4: social media channels.
Speaker 2: Absolutely other business website stuff.
Speaker 4: Yeah, always check out our website This podcast will kill
Speaker 4: You dot Com?
Speaker 3: Should we even go through?
Speaker 4: Like what's on the website? I mean everything? Is there
Speaker 4: anything that you could want? It's there? Yeah, it is.
Speaker 4: Should we just get started on this episode? Can we?
Speaker 4: Let's take a quick break and then dive straight in?
Speaker 4: West Nile virus is a flava virus, which listeners of
Speaker 4: this show should be very familiar with by now because
Speaker 4: we've covered so many other flava viruses, right, dange virus,
Speaker 4: yellow fever, hepatitis, see even so many viruses we're running
Speaker 4: out of laviviruses to cover. Just kidding, there's always more,
Speaker 4: but anyways, flaviviruses for anyone who hasn't listened to every
Speaker 4: one of our episodes, is a large family of RNA viruses,
Speaker 4: many of which are transmitted by arthropod vectors to animals
Speaker 4: and humans. West nilevirus causes a disease that primarily is
Speaker 4: what's called enzootic. That is, it has a cycle that
Speaker 4: is completely independent of humans. It's essentially a vector born
Speaker 4: disease of wildlife. This cycle is maintained in nature, specifically
Speaker 4: through an avian mosquito cycle. So birds and mosquitoes, where
Speaker 4: mostly mosquitoes in the genus Qlex feed on avian or
Speaker 4: bird hosts. They pick up the virus in their blood
Speaker 4: meal and then it passes through their gut, makes it
Speaker 4: to the salivary glands, they spit it back out, and
Speaker 4: then transmit it to other birds. And that's the primary cycle.
Speaker 4: Simple enough, Yeah, simple enough, especially compared to a lot
Speaker 4: of things that we cover. Will make it more complicated,
Speaker 4: don't worry.
Speaker 3: Oh yeah.
Speaker 4: It's thought that the virus is able to persist and
Speaker 4: perpetuate even in temperate regions of the world where adult
Speaker 4: mosquitoes aren't present all year round, both via adult mosquitoes
Speaker 4: that undergo diapause, so the virus persists in overwintering adults
Speaker 4: that are just not active. I have also seen that
Speaker 4: it's also possible that adult mosquitoes transmit it transovarially. I
Speaker 4: don't know how common that is, but it's also possible
Speaker 4: that migratory birds play a large role, bringing in virus
Speaker 4: from areas of higher transmission or places where you have
Speaker 4: year round transmission, or even just harboring low levels of virus,
Speaker 4: and then during their migration cycles bringing that virus back
Speaker 4: to temperate areas. But in any case, this avian mosquito
Speaker 4: cycle is the main enzootic cycle of West Nile virus,
Speaker 4: and birds are the predominant reservoir host for Westnile virus
Speaker 4: in North America alone. Hundreds of species of birds have
Speaker 4: been shown to be competent reservoir hosts, so harboring the
Speaker 4: virus whether or not they get sick and show symptoms,
Speaker 4: and the majority of bird species do seem to survive
Speaker 4: infection relatively unscathed. Don't worry, someone else is going to
Speaker 4: talk a lot more about this virus in birds. I'm
Speaker 4: going to focus on this virus in people. But other
Speaker 4: than birds and people, other animals can get infected as well. Importantly,
Speaker 4: horses also get infected relatively frequently, But humans and horses
Speaker 4: are what are called dead end hosts. That means that
Speaker 4: while we can become infected when a mosquito bites us
Speaker 4: and we can get sick, we can get clinical disease.
Speaker 4: Humans and horses don't actually contribute to the cycle of infection,
Speaker 4: so mosquitoes that then feed on us don't tend to
Speaker 4: become infected from feeding on infected people, right, And so
Speaker 4: I am going to focus on this disease as it
Speaker 4: manifests in humans. But like we kind of said upfront,
Speaker 4: it's also very important to understand the ecology and persistence
Speaker 4: of this disease is a lot more complex than just
Speaker 4: the human side of it. So we'll get to that
Speaker 4: and I'm really excited to get to that later. All Right,
Speaker 4: just focusing then on humans, let's talk about what it
Speaker 4: looks like when a person gets West Nile disease. First off,
Speaker 4: it's unclear exactly how infectious West Nile virus is. That is,
Speaker 4: how many people who get bitten by mosquitoes harboring West
Speaker 4: Nile virus actually go on to become infected. We don't
Speaker 4: really know well.
Speaker 2: And I would also imagine that the amount of virus
Speaker 2: varies mosquito to mosquito.
Speaker 4: Definitely absolutely, I would yes. So we really don't know
Speaker 4: what the overall infectiousness of Westnile virus is, but we
Speaker 4: do know that of those people who get infected, about
Speaker 4: twenty five percent some estimates say twenty to forty percent,
Speaker 4: but most that I've seen are around twenty or twenty
Speaker 4: five percent of people will develop symptomatic disease aka West
Speaker 4: Nile fever, and about one in one hundred and fifty
Speaker 4: to two hundred and fifty, or less than one percent
Speaker 4: of those people will develop what's called neuroinvasive disease or
Speaker 4: sometimes it's called WNND Wesnile neuroinvasive disease. And this includes
Speaker 4: one of three possible rologic manifestations that are common. And
Speaker 4: then there's also honestly any range of neurologic complications that
Speaker 4: can happen, but the three big ones are West Nile encephalitis,
Speaker 4: West Nile meningitis, and West Nile acute flaccid paralysis. And
Speaker 4: because I know you're gonna ask me, Aaron, we don't
Speaker 4: fully know why exactly it is that some people get
Speaker 4: invasive disease and others don't. But I know I can
Speaker 4: see you're down trotic face, It's true, we have some ideas. Okay,
Speaker 4: it's likely a combination of that viral load like you
Speaker 4: already mentioned, so how much virus do you get injected
Speaker 4: with from this mosquito to begin with, and then a
Speaker 4: lot of other individual risk factors like older age, especially
Speaker 4: over age sixty five or seventy is very strongly associated
Speaker 4: with increased risk of neuroinvasive disease, and then other things
Speaker 4: like hypertension, kidney disease, things that are affect your overall
Speaker 4: immune status. Also, West Nile virus being a disease transmitted
Speaker 4: by mosquitoes into your bloodstream is a disease that can
Speaker 4: also then potentially be transmitted from things like organ transplants,
Speaker 4: and people who have gotten West Nile infection from things
Speaker 4: like organ transplants are also far more likely to develop
Speaker 4: neuroinvasive disease compared to those that get infected from mosquitoes. Interesting, okay,
Speaker 4: but that is very rare. I'm just saying so. Generally,
Speaker 4: the incubation period for Westnile fever is anywhere from two
Speaker 4: to fourteen days most of the time, and symptoms can
Speaker 4: really range from a pretty mild, almost flu like illness
Speaker 4: to like I mentioned a very debilitating neuroinvasive disease, but
Speaker 4: in most people it often starts like this, a sudden
Speaker 4: onset of headache, very sudden onset of a pretty bad headache,
Speaker 4: generalized malaise, just feeling really crappy, a fever, muscle aches,
Speaker 4: and then fatigue, And very often as this fever starts
Speaker 4: to subside, a rash will develop, usually along the torso
Speaker 4: and then extending out to the arms and legs. And
Speaker 4: this rash actually looks kind of like the rash from measles.
Speaker 4: So it's like what we call maculo popular. It's little red,
Speaker 4: flat little spots with raised little bumps inside. Yeah, it's
Speaker 4: the kind of rash that really like, a lot of
Speaker 4: different viruses cause similar rashes. Unlike measles, this doesn't tend
Speaker 4: to go head down. This is just like a torso
Speaker 4: to extremities type rash. Why why great question? I have
Speaker 4: the slightest idea. Honestly, a lot of viruses cause similar
Speaker 4: rashes like this. So whether it's a combination of the
Speaker 4: damage that that virus is doing to your cells versus
Speaker 4: just that kind of generalized immune response causing that rash,
Speaker 4: I don't know the answer. Yeah, rashes, rashes, let's ask
Speaker 4: a dermologist. I don't know.
Speaker 2: I have a question about the complications the neuroinvasive disease.
Speaker 4: Oh, don't worry, We're going to get there, Aaron.
Speaker 2: Okay, But I'm just the breakdown among them. So you
Speaker 2: mentioned the three different kinds. Yeah, what is the breakdown
Speaker 2: of those?
Speaker 4: That's a good question. I actually don't have a good
Speaker 4: handle on the breakdown everything. Just sort of said less
Speaker 4: than one percent will develop these complications, okay. And part
Speaker 4: of it, I think is probably because there's a bit
Speaker 4: of a spectrum, like it doesn't mean that you maybe
Speaker 4: only have one of the three. You might have some
Speaker 4: acute flaccid paralysis with a little meningitis. You might have
Speaker 4: a meningio encephalitis. Yeah, but that's a good question. Also,
Speaker 4: I think because it is so rare, we probably don't
Speaker 4: have really good numbers to be able to break it
Speaker 4: down when it's less than one percent. Okay, okay, But
Speaker 4: the rash back to that that those type of kind
Speaker 4: of mild symptoms can last anywhere from a handful of
Speaker 4: days to up to a few weeks, So this can
Speaker 4: be a pretty prolonged course of illness, even if it's
Speaker 4: not severe. Now, if it progresses to that narrow invasive disease,
Speaker 4: the symptoms then just kind of look like whatever part
Speaker 4: of your nervous system is being invaded by this virus. So,
Speaker 4: in the case of West Nile meningitis, the symptoms look
Speaker 4: like meningitis, which is a sudden onset of fever, a
Speaker 4: very very massive headache, stiff neck, photophobia which is difficulty
Speaker 4: looking at light and it becomes very painful to look
Speaker 4: at light. If it progresses to encephalitis, then you often
Speaker 4: have those same meningial symptoms, but then you also will
Speaker 4: have things like altered level of consciousness, which means you
Speaker 4: can slip into a coma essentially, or just personality changes
Speaker 4: because of swelling and inflammation in different areas of your
Speaker 4: actual brain. And West Nile encephalitis tends to be the
Speaker 4: most severe with the worst outcomes.
Speaker 2: Okay, and so this might be a very basic question,
Speaker 2: But does it always progress meningitis and then encephalitis.
Speaker 4: No, not necessarily, and we'll get to that in just
Speaker 4: a minute kind of maybe, well, let me just keep going.
Speaker 4: So West Nile virus also then can cause acute flaccid
Speaker 4: paralysis aarin. Do you remember what other disease we've covered
Speaker 4: that does the exact same thing. Oh you remembered so quickly.
Speaker 2: Well, okay, but I have to confess I've watched like
Speaker 2: a bunch of YouTube on West Nile virus, and there
Speaker 2: was one where like a physician came on and talked
Speaker 2: about it, yeah, and was like, I haven't seen a
Speaker 2: polio case, but this is apparently exactly like polio.
Speaker 4: Yeah, they actually call it poliomyelitis, even though it's caused
Speaker 4: by a completely different virus, which I think confuses me.
Speaker 4: It confused me too. It was like, but wait, yeah,
Speaker 4: but basically what can happen is that if West Nile
Speaker 4: virus specifically infects the anterior horn cells of the spinal cord.
Speaker 4: This is the part of our spinal cord where our
Speaker 4: motor neurons exit the spinal cord, that is the exact
Speaker 4: same area that poliovirus infects and causes swelling and then damage.
Speaker 4: And so this looks just like polio did. Your muscles
Speaker 4: and your limbs go weak. In the case of West
Speaker 4: Nile virus, it's often asymmetric, so it can look a
Speaker 4: lot like a stroke.
Speaker 3: Interesting.
Speaker 4: It is interesting. Why is it asymmetric. I don't know,
Speaker 4: and it's not always. It's just that oftentimes it can
Speaker 4: be okay. Presumably it's just that this is where the
Speaker 4: virus ended up.
Speaker 2: So if somebody goes to the hospital and presents with
Speaker 2: acute flaccid paralysis, are there other things like or is
Speaker 2: West Nile sort of top of the list? I mean,
Speaker 2: depending of course on geography, their history, et cetera.
Speaker 4: Depending It would depend on all those things. And West
Speaker 4: Nile virus. Of course, polio can also cause it, but
Speaker 4: that's generally not around most of the world these days.
Speaker 4: I don't know if there are other viruses. I imagine
Speaker 4: there are a handful of other viruses that can do that.
Speaker 4: One way that might differentiate this from stroke could be
Speaker 4: a range, especially if it's someone who has no other
Speaker 4: risk factors coming in. Importantly, West Nile virus tends to
Speaker 4: not affect your cranial nerves, and strokes often do so
Speaker 4: if you think of they have like those you know,
Speaker 4: public information campaigns about looking for a drooping face. That's
Speaker 4: when your cranial nerves are affected, which tends to not
Speaker 4: be affected with West Nile. In fact, in many cases
Speaker 4: West Nile acute flacid paralysis can mimic gion Beret disease. Huh,
Speaker 4: but gion Beret usually has sensory symptoms as well, and
Speaker 4: West Nile tends to not, although it can huh. Okay,
Speaker 4: I know it's complicated. It's complicated. And with any of
Speaker 4: these neuroinvasive versions of West Nile virus, you may also
Speaker 4: have some other signs things like nausea, vomiting, you might
Speaker 4: have a rash, you might have vision changes. So it's
Speaker 4: the constellation of all these symptoms. It tends to not
Speaker 4: just be one symptom isolated. And some people have like
Speaker 4: a viral prodrome, so some kind of mild viral type
Speaker 4: symptoms fever, chills, feeling cruddy, pride to the onset of
Speaker 4: these invasive symptoms. Others don't or at least don't remember
Speaker 4: having one. So the good news is that for most
Speaker 4: cases of West Nile virus, even the neuroinvasive cases, people
Speaker 4: tend to make a full recovery. However, the worst outcomes
Speaker 4: do tend to be in people who progress to encephalitis.
Speaker 4: And when we look at all of the neuroinvasive disease
Speaker 4: lumped together, so this is meningitis encephalitis AFP, but really
Speaker 4: the fatality tends to come from encephalitis or meningitis. In
Speaker 4: those neuroinvasive disease cases, the case fatality rate can be
Speaker 4: as high as ten percent overall, or even higher for
Speaker 4: those that are older than seventy and for many, many people,
Speaker 4: especially with this neurologic symptoms, the recovery process can be
Speaker 4: very very slow, taking up to a year or more.
Speaker 4: And in some cases, especially with this acute flacid paralysis
Speaker 4: or in some cases with encephalitis, people may lose function
Speaker 4: that they never are able to regain because nerves are damaged.
Speaker 4: Things are damage that just are not able to recover, and.
Speaker 2: The damage is caused by just inflammation by the viruses,
Speaker 2: you know, being there.
Speaker 4: Yeah, So that's the question, right, right, right, that's the
Speaker 4: what is the what is the path of physiology of
Speaker 4: this disease? I haven't even I haven't even started to
Speaker 4: talk about it. So here let's try, shall we. Let's
Speaker 4: do it? Okay, So, being a virus, we all know
Speaker 4: by now that viruses have to invade our cells in
Speaker 4: order to cause disease. It's thought that initially, primarily when
Speaker 4: we get infected, one of the major cells that West
Speaker 4: Nile virus tends to infect are our dendritic cells, which
Speaker 4: are one of our immune cells that usually help to
Speaker 4: present antigens to our immune system like a flag so
Speaker 4: that we can make antibodies. So it's a pretty good
Speaker 4: cell for a virus to hide within, and westnilvirus, like
Speaker 4: many other flavaviruses, is very good at suppressing our overall
Speaker 4: immune response to infection. So as it invades these dendritic cells,
Speaker 4: those cells travel to our lymph nodes because that's where
Speaker 4: they like to go to present their antigens. But westnilvirus
Speaker 4: is then able to escape from those dendritic cells from
Speaker 4: our lymph nodes, enter our blood stream and travel wherever
Speaker 4: it wants. And as we've just gone over, one of
Speaker 4: the big hallmarks of west nile virus is that it
Speaker 4: somehow can make it from our blood stream into our
Speaker 4: central nervous system, our spinal cord, our Meningji's or our
Speaker 4: actual brain. So how is it actually able to do this? Like,
Speaker 4: how can it be so neuroinvasive? We're supposed to have
Speaker 4: a blood brain barrier that's supposed to literally stop this,
Speaker 4: and the answer is that we don't know exactly how
Speaker 4: it's able to do this. How is it so good
Speaker 4: at evating our immune response and making its way into
Speaker 4: our central nervous system. There are four at least different hypotheses.
Speaker 4: One is that it just releases or causes us to
Speaker 4: release a lot of cytokines. Probably a lot of people
Speaker 4: have heard of cytokines by now because of COVID and
Speaker 4: our influenza episode way back when. But these basically just
Speaker 4: increase the permeability of our vascular membranes, allowing more things
Speaker 4: to pass through. It's so that inflammation can get in
Speaker 4: there to do its job, but it also allows for
Speaker 4: viruses to make it across that blood brain barrier. That's
Speaker 4: one hypothesis. The second is that it actually just can
Speaker 4: warm its way by entering through our endothelial cells, those
Speaker 4: cells that line the blood brain barrier. It can invade
Speaker 4: those cells and then make it through. Another possible hypothesis
Speaker 4: is that it invades via macrophages. Ah right, So macrophages
Speaker 4: are another one of our white blood cells that sometimes
Speaker 4: move across the blood brain barrier for our protection. But
Speaker 4: this virus can potentially be harbored within those macrophases. And finally,
Speaker 4: my favorite hypothesis is maybe it does a little bit
Speaker 4: of rabies and it actually travels on our neurons and
Speaker 4: does retrograde axonal transport all the way to our central
Speaker 4: nervous system.
Speaker 3: Ah, that is scary.
Speaker 4: Yeah, and we don't know, We don't know which of
Speaker 4: those tends to be the biggest driver and why. Huh. Yeah,
Speaker 4: it's especially interesting because again, neuroinvasive disease can be very serious,
Speaker 4: but it's very rare in West Nile, and yet it's
Speaker 4: also one of the most common causes of viral certainly
Speaker 4: of vector borne viral and stephal in North America. Right. Interesting,
Speaker 4: it's very interesting. So I don't have a good answer
Speaker 4: for you erin in terms of how much of this
Speaker 4: damage is caused by viral damage directly versus our immune
Speaker 4: response and inflammation therein, because we don't even fully understand
Speaker 4: how this virus even makes it into our central nervous
Speaker 4: system to begin with.
Speaker 2: So there are other flavvy viruses that invade the central
Speaker 2: nervous system, certainly, And do we know the mechanisms for this,
Speaker 2: I don't.
Speaker 4: I don't, But I imagine that these hypotheses that have been proposed,
Speaker 4: which I didn't come up with have been proposed based
Speaker 4: on both mouse models of West Nile virus infection as
Speaker 4: well as other similar flavaviruses like Japanese encephalitis, etc.
Speaker 3: That makes sense.
Speaker 4: Yeah, so that's kind of the overall biology. It is,
Speaker 4: I will say, relatively easy to diagnose, but also of
Speaker 4: course difficult to diagnose in other ways. Mainly, we tend
Speaker 4: to diagnose by looking for antibodies to the virus, which
Speaker 4: tend to be apparent after about eight days after the
Speaker 4: onset of symptoms. Most of the time you can find
Speaker 4: them after that amount of time, but you have to
Speaker 4: be able to test like between eight and twenty one
Speaker 4: days after symptoms start for that test to be accurate.
Speaker 4: You can test for the virus itself, but then those
Speaker 4: tests are sometimes hard to come by depending on where
Speaker 4: you live, etc.
Speaker 2: I've also read that it's not easily detectable because humans
Speaker 2: tend to like circulate less virus in.
Speaker 4: Their bloods right very low levels of virus. And then
Speaker 4: it also depends on are you testing blood or are
Speaker 4: you testing cerebrospinal fluid for meningitis or is it just
Speaker 4: for like a general and felt in general. At least
Speaker 4: as far as I could tell we don't have any
Speaker 4: specific antiviral treatment for West Nile virus, so treatment is
Speaker 4: just supportive, the way that you would treat anybody with
Speaker 4: a meningitis or an encephalitis that's not bacterial, So just
Speaker 4: sort of supportive care. And that is the biology of
Speaker 4: West Nile. Aaron, I know you have a lot to
Speaker 4: tell me about where this sole virus came from. I
Speaker 4: do Okay, good shall.
Speaker 2: We Yeah, I'll dive in as soon as we take
Speaker 2: a quick break. Well, actually, Aaron, this history section is
Speaker 2: gonna be kind of like a total break from the
Speaker 2: last few episodes we've done.
Speaker 4: Okay in what way?
Speaker 2: Well, okay, diabetes absolutely enormous history, Anthrax.
Speaker 4: Huge, oh my gosh, so big.
Speaker 2: Yeah, Shaga disease, super extensive history, all of it. But
Speaker 2: the history of West Nile, although it does date back,
Speaker 2: you know, probably further than you might think, it's fairly
Speaker 2: what I would say, that's straightforward, okay, Which isn't to
Speaker 2: say like, that's not to say that it's uninteresting or
Speaker 2: that it can't tell us anything about big picture science
Speaker 2: or big picture society or big picture public health issues,
Speaker 2: because it definitely can.
Speaker 4: Oh, I have no doubt Aaron.
Speaker 2: But before we get to that, we have to start
Speaker 2: back a bit of course. Where did this virus come from?
Speaker 2: And how did we get to where we are today
Speaker 2: with it?
Speaker 4: And what did they say in the ebers pavirus Well,
Speaker 4: sadly or not sadly, I don't know.
Speaker 2: It doesn't seem to be mentioned, at least that I
Speaker 2: could gather try So, like you mentioned, Aaron, West Nile
Speaker 2: virus is a flavvy virus, and it's related to other
Speaker 2: flavvy viruses, like you know, the ones you named yellow
Speaker 2: fever virus, which I honestly it's been so long that
Speaker 2: I don't remember if I covered this in that episode.
Speaker 2: But the name flavvy virus actually comes from the Latin
Speaker 2: word flavus for yellow, which I also think then kind
Speaker 2: of adds a fun little layer to the base to
Speaker 2: the recipe for our drink.
Speaker 4: Yeah, yeah, I agree. Also, I can't remember if you
Speaker 4: said that in Yellow Fever either, so I'm glad that
Speaker 4: you told us again.
Speaker 2: Yeah, but yeah, danky virus, seek a virus, Japanese encephalitis virus,
Speaker 2: Saint Louis and cephalitis virus, take born encephalitis virus, and.
Speaker 4: So on, so many so many, many, and.
Speaker 2: Of all of these flavvy viruses, West Nile virus is
Speaker 2: one of the earliest described and one of the most
Speaker 2: widely distributed.
Speaker 7: Huh, yeah, I know, it was a little surprising. Yeah,
Speaker 7: I knew it was widely distributed. I didn't know it
Speaker 7: was one of the earliest ones get.
Speaker 4: Into Oh I am.
Speaker 2: So we can use things like zerological studies and genomic
Speaker 2: analyses to tell us how it came to have what
Speaker 2: is basically this global distribution, and what it looks like
Speaker 2: is that West Nile virus evolved in Africa. I don't
Speaker 2: have an exact or even a rough date estimate for that,
Speaker 2: or an exact location or even a rough location, but
Speaker 2: that's where serological studies show that the virus is circulating
Speaker 2: continuously and has been that way for quite some time.
Speaker 2: And this year round transmission is in contrast with the
Speaker 2: past veterans in other places such as Europe, where West
Speaker 2: Nile virus was introduced from Africa via migratory birds and
Speaker 2: where it tends to pop up in this more seasonal
Speaker 2: transient form. And West Nile virus was brought to India
Speaker 2: via trade, probably around like the early eighteen hundreds, eighteen
Speaker 2: twenties or so when there was extensive trade between Africa
Speaker 2: and India, and then to like Australia or the Australasia
Speaker 2: region in the mid eighteen hundreds. And this last one,
Speaker 2: like how it got to Australia is a bit of
Speaker 2: a mystery because there are apparently no bird migrations that
Speaker 2: connect Australia and Africa. Although any bird friends nick, yeah,
Speaker 2: Fred Cole, Maria Nate nick, we.
Speaker 4: Have a lot of bird friends.
Speaker 2: Do have a lot of bird friends, way in if
Speaker 2: you know something else, but yeah, so it because of that,
Speaker 2: it's been suggested that West nolevirus was actually introduced to
Speaker 2: Australia from Africa in a similar way that yellow fever
Speaker 2: virus was brought to North America from infected mosquitoes on
Speaker 2: ships carrying enslaved people as Europeans traveled to Australia from Africa.
Speaker 2: Oh okay, And it seems that really the only place
Speaker 2: where Westnile virus is not present besides like the Arctic
Speaker 2: and Antarctica, is in a lot of parts of Eastern Asia,
Speaker 2: and the reasons for that are not quite clear. Maybe
Speaker 2: it's like a competition thing with other encephalitis viruses, I
Speaker 2: don't know. A mosquito incompatibility, hosting compatibility.
Speaker 3: I don't know.
Speaker 2: And I'm not going to get too much into the
Speaker 2: details of like the different lineages and the clades that
Speaker 2: the virus can be broken down into, because there's a lot,
Speaker 2: but just to say that they do exist and that
Speaker 2: they can help us in new outbreaks to see where
Speaker 2: the virus is coming from and identify ways that it
Speaker 2: got there. For instance, like was it a single introduction
Speaker 2: event or multiple It's thought that West Nile virus was
Speaker 2: introduced to Europe and North America in several independent introduction events,
Speaker 2: while it was brought to Australia in just one. And
Speaker 2: then how much has the virus evolved since arriving in
Speaker 2: a new area? Are there path of physiological differences among
Speaker 2: the different clades that could have clinical implications or ecological
Speaker 2: differences that could change the way we control it, et cetera.
Speaker 2: So it's a useful area. It's just like a lot
Speaker 2: of minute detail that sort of open ended questions in
Speaker 2: some ways.
Speaker 4: Yeah.
Speaker 2: Yeah, So I mentioned that West Nile virus was one
Speaker 2: of the earliest described flappy viruses, but the way that
Speaker 2: it happened was kind of a fluke.
Speaker 4: Oh yeah, oh yeah.
Speaker 2: In nineteen thirty seven, researchers were conducting a wide scale
Speaker 2: epidemiological study on yellow fever in Uganda and a person
Speaker 2: from the West Nile District of Northern Uganda was brought
Speaker 2: into the study presenting with a fever. But when they
Speaker 2: tested this person's serum against yellow fever virus, it didn't match. Instead,
Speaker 2: it looked to be more similar to other flabby viruses
Speaker 2: that caused encephalitis, Saint Louis encephalitis and Japanese b encephalitis viruses,
Speaker 2: and even though the person only had a fever, they
Speaker 2: noted that it seemed to have neurotropic tendencies. The researchers
Speaker 2: described this new virus in a paper in nineteen forty,
Speaker 2: which is like older than I expected for we style virus.
Speaker 4: It really is.
Speaker 2: Yeah. Also, I just have to complain here for a
Speaker 2: second because that paper published in nineteen forty is eighty
Speaker 2: one years ago. Yeah, is still behind a paywall?
Speaker 4: Are you serious?
Speaker 3: I am serious.
Speaker 4: That's ridiculous.
Speaker 2: Yeah, I mean, like, can we just make everything open access?
Speaker 2: It would make the world of place.
Speaker 4: Okay, eighty one years old, I know, I know.
Speaker 2: Wow, frustrating anyway, So why did I call the discovery
Speaker 2: of West Nile virus a fluke? Well, for one, it
Speaker 2: was discovered kind of accidentally, like those researchers weren't out
Speaker 2: looking for the cause of an outbreak of unexplained febrile illness.
Speaker 2: And for two over the next sixty years or so
Speaker 2: after its discovery, westnyle virus was not really considered that much, like,
Speaker 2: it didn't rank that highly on the list of pathogens
Speaker 2: of public health importance. Yeah, now, there were a lot
Speaker 2: of other and there still are a lot of other
Speaker 2: mosquito born viruses that cause a lot more widespread morbidity
Speaker 2: and mortality, and so West Nile virus was kind of
Speaker 2: just like, oh, that's just another one of those flappy viruses, right.
Speaker 2: And the third reason is that you know, like we
Speaker 2: talked about in the biology, the virus isn't often easily
Speaker 2: isolated and infected humans like in blood. So the fact
Speaker 2: that they were able to ice related at all, I
Speaker 2: think is kind of interesting. So it wasn't until the
Speaker 2: nineteen fifties that the first outbreaks of West Nile virus
Speaker 2: were observed, like the first time that people recognized that
Speaker 2: West Nile virus could be capable of causing widespread outbreak.
Speaker 4: Like an outbreak, not just like an incidental disease here
Speaker 4: and there exactly.
Speaker 2: And that started with the first recognized epidemic in Israel
Speaker 2: in nineteen fifty one, one hundred and twenty three cases
Speaker 2: occurred in a small town the size of three hundred
Speaker 2: and three people.
Speaker 4: I'm sorry, you said, one hundred and sixty cases in
Speaker 4: a one hundred and three hundred.
Speaker 2: One hundred and twenty three out of three hundred people here.
Speaker 4: Oh my goodness, I know that's a pretty high attack rate,
Speaker 4: really really high.
Speaker 2: No fatalities occurred, and in fact, most of the people
Speaker 2: affected were children. But this was the first time, really
Speaker 2: that the various disease symptoms that this virus can cause
Speaker 2: were recognized, things like you already mentioned, you know, fever, headache,
Speaker 2: abdominal pain, vomiting, etc. And around the same time as
Speaker 2: this epidemic in Israel or not long after, a series
Speaker 2: of outbreaks of West Nile virus popped up in Egypt.
Speaker 2: And during these outbreaks a lot more ground was covered
Speaker 2: in terms of understanding the disease ecology, clinical characteristics, and
Speaker 2: epidemiological patterns for instance, this is when researchers realized that
Speaker 2: a large proportion of people infected never showed any symptoms,
Speaker 2: that children in these areas tended to have more symptomatic illness,
Speaker 2: but adolescents and adults tended to have higher zero prevalence,
Speaker 2: so suggesting that like in these places where the virus
Speaker 2: was endemic and like continuously circulating, people were likely exposed
Speaker 2: to the virus at a young age.
Speaker 4: Interesting. Interesting, interesting Yeah.
Speaker 2: And researchers also in these early outbreaks in the nineteen
Speaker 2: fifties found the virus in many species of birds and
Speaker 2: also in some species of mammals, and this is when
Speaker 2: they made the link between mosquitos.
Speaker 3: And the virus.
Speaker 4: Okay, cool, wow, a lot oh yeah, a.
Speaker 3: Lot of ground.
Speaker 4: Yeah.
Speaker 2: And finally, some of the neurological complications of infection were
Speaker 2: observed during these early outbreaks in Israel and Egypt, things
Speaker 2: like these rare instances of meningitis or encephalitis. But overall,
Speaker 2: these outbreaks really kind of served to reinforce the idea
Speaker 2: in many ways that West Nile virus was mostly asymptomatic
Speaker 2: or if anything, generally like a mild mosquito born illness.
Speaker 2: And this prevailing perception can be seen in the experimental
Speaker 2: infection studies that took place in Egypt during this time,
Speaker 2: where people with terminal cancer were intentionally infected with the
Speaker 2: virus to see if the resulting fever would help suppress
Speaker 2: the cancer's growth.
Speaker 4: Oh gosh, well, this was actually.
Speaker 2: Apparently like a fairly common or at least occasional type
Speaker 2: of experimental treatment during this time that people were like
Speaker 2: exploring or looking into interesting.
Speaker 4: Was it effective?
Speaker 6: So?
Speaker 2: I don't know, because again I don't have access to
Speaker 2: this old paper either.
Speaker 8: From grade nineteen fifties, which is kind of annoying, which
Speaker 8: also means that I couldn't read between the lines to
Speaker 8: see whether this falls under you know, actual experiment or
Speaker 8: medicalized torture.
Speaker 2: You know, does volunteer have quotes around it? Yeah, et cetera. Ok, Yeah,
Speaker 2: but these studies were terminated when several of the people
Speaker 2: who were infected developed encephalitis.
Speaker 4: Makes sense, Yeah, reasonable stopping point.
Speaker 2: But during these studies, the researchers also did make some
Speaker 2: important observations in terms of things like viremia, like how
Speaker 2: much virus was circulating and when and how long it
Speaker 2: could be detected, and how the amount of virus circulating
Speaker 2: correlated with the severity disease.
Speaker 4: Okay, So following.
Speaker 2: These outbreaks in Egypt and Israel, West Nile virus continued
Speaker 2: to make sporadic appearances across parts of Africa, the Mediterranean
Speaker 2: and Europe, popping up in France, South Africa, Russia, Spain,
Speaker 2: and India and some other places. And in the course
Speaker 2: of these epidemics, it became more apparent that this virus
Speaker 2: can absolutely cause neurological disease in some people, which might
Speaker 2: have brought it more research attention at the time. So
Speaker 2: like in the fifties and sixties, if not for the
Speaker 2: fact that large outbreaks of the virus all but stopped
Speaker 2: throughout the nineteen seventies and nineteen eighties, like they just
Speaker 2: I don't know whether it was just like observation plummeted,
Speaker 2: or the ecology made it to just like really put
Speaker 2: it in a lull period.
Speaker 4: I don't know.
Speaker 2: But in nineteen ninety six, a new era of West
Speaker 2: Nile virus began, first with a large epidemic in southern Romania.
Speaker 4: And not only was this one of the.
Speaker 2: Biggest recognized outbreaks of West Nile virus, with at least
Speaker 2: three hundred and ninety three hospitalizations and seventeen deaths, and
Speaker 2: who knows how many actual infections, But it also involved
Speaker 2: a lot of neurological cases, and it was the first
Speaker 2: to happen in what was basically a mostly urban area,
Speaker 2: whereas previous outbreaks had been more rural. And over the
Speaker 2: next couple of years it became clear that this wasn't like,
Speaker 2: this wasn't a one off. West Nile virus seemed to
Speaker 2: be undergoing a change in its epidemiology After the epidemic
Speaker 2: in Romania. The virus popped up in Morocco in nineteen
Speaker 2: ninety six, in Tunisia in nineteen ninety seven, in Italy
Speaker 2: and Israel in nineteen ninety eight, and in Russia in
Speaker 2: nineteen ninety nine, and like the nineteen ninety six Romanian outbreak,
Speaker 2: these were also in urban areas, seemed to have higher
Speaker 2: rates of neurological involvement with a higher fatality, and had
Speaker 2: a tendency to impact mostly people in older age groups.
Speaker 2: So by the time August nineteen ninety nine rolled around,
Speaker 2: the pattern had already been set. But West Nyle virus
Speaker 2: still held one more big surprise for everyone, and that
Speaker 2: was that it had made the leap across the ocean
Speaker 2: and into North America.
Speaker 4: Ooh, big splash, big splash.
Speaker 2: So far West style virus I think has taught us
Speaker 2: a couple of really important lessons, or at least like
Speaker 2: reemphasize them. And since Aaron, you're like, we've talked about
Speaker 2: this many times and listeners, if you've tuned in before,
Speaker 2: these are going to sound familiar, but I'm gonna say
Speaker 2: them anyway. The first is to not underestimate a virus.
Speaker 4: Never underestimate a virus.
Speaker 2: Yeah, many viruses that appeared mild at first can go
Speaker 2: on to have serious complications or long term effects. Not all,
Speaker 2: of course, but the potential is there. Like remember chicken.
Speaker 4: Pox for instance.
Speaker 3: Remember it.
Speaker 2: And the second lesson is that human movement and human
Speaker 2: modification of the environment can alter the dynamics of infection
Speaker 2: in a very major way. Yeah, this isn't new stuff,
Speaker 2: but it's definitely important stuff. And so these two lessons
Speaker 2: were also learned during what would be the first epidemic
Speaker 2: of West Nile virus in North America, beginning in August
Speaker 2: of nineteen ninety nine. But that outbreak also carried with
Speaker 2: it another hugely important warning. Human health is wildlife health
Speaker 2: is domestic animal health is environmental health. It's all connected.
Speaker 4: What's that, It's all connected. What's that A one health approach, A.
Speaker 3: One health approach.
Speaker 2: So let's get into it. Do you remember the nineteen
Speaker 2: ninety nine West Nile virus outbreak at all?
Speaker 4: You know, I've I remember when West Nile virus became
Speaker 4: a thing because my dad had a pond in the
Speaker 4: backyard and it was like, oh no, we can't have
Speaker 4: a pond anymore because West now virus made it to California.
Speaker 4: Mm huh. Yeah.
Speaker 6: Yeah.
Speaker 2: I don't remember specifically, like the nineteen ninety nine one,
Speaker 2: but I remember suddenly it was like West Nile mosquitoes. Yeah,
Speaker 2: you know, put on that off whatever all the time.
Speaker 2: All I knew was that it appeared and then that
Speaker 2: was it.
Speaker 4: Yeah.
Speaker 2: So let me fill in some of the details.
Speaker 4: Some of our gaps and memory.
Speaker 6: Yeah.
Speaker 4: Yeah.
Speaker 2: So, beginning in the summer of nineteen ninety nine, all
Speaker 2: over New York City, crows started dropping dead. It was
Speaker 2: like dropping out of the sky, just dead. Everywhere you
Speaker 2: went you could find the carcasses of dead crows. And
Speaker 2: maybe if you lived in New York City at the time,
Speaker 2: you might have seen some of these dead crows and thought,
Speaker 2: oh gross, these poor crows, probably rat poison. Who knows,
Speaker 2: bad pizza? I don't know, and then went on with
Speaker 2: your day. But the sight of these crows brought a
Speaker 2: lot more alarm to one person, in particular, doctor Tracy McNamara,
Speaker 2: who was the lead pathologist at the Bronx Zoo. If
Speaker 2: these crows were dying of some kind of infectious disease,
Speaker 2: the birds at the zoo, some of which were rare
Speaker 2: or endangered, were at serious risk. And that risk soon
Speaker 2: became a reality when some of the zoo birds began
Speaker 2: to die, starting with a snowy owl. Oh no, And
Speaker 2: this definitely pointed towards an infectious agent.
Speaker 4: But like, what was it?
Speaker 2: Doctor McNamara examined some brain tissue from the dead birds
Speaker 2: under the scope to try to answer that question, and
Speaker 2: what she saw, in her own words, took her breath away.
Speaker 4: Wow.
Speaker 2: Quote, it was the worst encephalitis I'd seen in eighteen
Speaker 2: years as a comparative pathologist.
Speaker 4: Just yeah, staggering.
Speaker 2: Not far away at Flushing Hospital in Queens, an unusual
Speaker 2: number of encephalitis cases began coming in, some with paralysis
Speaker 2: and some leading to death, but these were in humans
Speaker 2: rather than birds.
Speaker 3: Just to clarify, and.
Speaker 2: These encephalitis cases were clustered enough in time and space
Speaker 2: to make an infectious disease specialist at the hospital, doctor
Speaker 2: Debbie Asns, wonder whether there might be a link among them,
Speaker 2: so she brought in the Department of Health to ask
Speaker 2: the patient's question after question about where they ate, what
Speaker 2: they ate, where they worked, where they lived, what train
Speaker 2: they rode, what shampoo they used, and so on. The
Speaker 2: only commonality among them seemed to be that they enjoyed
Speaker 2: spending a lot of time outside, especially in the evenings,
Speaker 2: and household surveys of where they lived showed that there
Speaker 2: had been a lot of mosquito breeding habitats around. Could
Speaker 2: it be a mosquito born out break? It had been
Speaker 2: a long time since something like that had happened in
Speaker 2: New York. Yeah, I remember, this was before Zeka.
Speaker 4: This was like way before, way before before. Yeah, this
Speaker 4: is like but it was.
Speaker 2: Still a possibility, like enough so that doctor Asnes sent
Speaker 2: off samples to the CDC to have them test for
Speaker 2: any known infectious agents, which side note deserves some major
Speaker 2: props because there are plenty of doctors who would have
Speaker 2: chalked up the cases to coincidence, like there isn't always
Speaker 2: an answer in medicine, and there are plenty of unexplained
Speaker 2: fevers or illnesses that resolve themselves without revealing what they
Speaker 2: really are. And so for doctor Asnes to send out
Speaker 2: those samples is like in many ways, I think going
Speaker 2: above and beyond and likely helped enact control measures earlier than.
Speaker 3: They would have otherwise.
Speaker 2: And so off those samples went to the CDC, and
Speaker 2: before long they came back with a match with an answer,
Speaker 2: Saint Louis and cephalitis virus. And this seemed like a
Speaker 2: reasonable explanation. Saint Louis and cephalitis virus is a rare
Speaker 2: mosquito born virus that can, as its name suggests, cause encephalitis,
Speaker 2: and it's a flabby virus.
Speaker 4: But that answer, which.
Speaker 2: Was now by this time reported in the news outbreak
Speaker 2: of Saint Louis and cephalitis, that didn't sit right with
Speaker 2: doctor Tracy and McNamara. After hearing about the human encephalitis cases,
Speaker 2: she felt very strongly that there was a link between
Speaker 2: those cases and the sick and dying birds at the zoo.
Speaker 2: But if she was right and there was such a link.
Speaker 2: It couldn't be Saint Louis and cephalitis virus because birds
Speaker 2: can't get that virus.
Speaker 4: And so she reached out to.
Speaker 2: The CDC with her concerns and urged them to test
Speaker 2: some of her samples to see if there was a
Speaker 2: match to the human samples. But the CDC turned her
Speaker 2: down really really okay, partly because it was a bureaucracy thing. Yeah,
Speaker 2: like the testing of animal samples, all animal health stuff
Speaker 2: that fell under the jurisdiction of like the USDA, I think,
Speaker 2: And it was a totally different like the CDC in
Speaker 2: some ways. They were like, well, we don't have the
Speaker 2: capabilities to do this. This isn't like we're not allowed
Speaker 2: to do this in the you know.
Speaker 4: Yeah, the job in trip. It's so interesting because as
Speaker 4: you were saying, like she reached out to the CDC,
Speaker 4: I was like, Wow, how does one just reach out
Speaker 4: to the CDC? Like that's a good question.
Speaker 2: I mean, I guess if you're like the lead pathologists
Speaker 2: at a zoo, you might have some.
Speaker 4: I would think you'd have an in somehow. Yeah, but
Speaker 4: it's a bummer that she couldn't get around whatever bureaucracy existed.
Speaker 2: It was bureaucracy. But I think the other part was
Speaker 2: that she kind of ran into a lot of resistance
Speaker 2: wherever she faced. And that's like, that's how she described
Speaker 2: it because at that time, like there was this prevailing
Speaker 2: attitude that, you know, human health and wildlife health weren't
Speaker 2: necessarily connected, and so the death of a few birds
Speaker 2: at a zoo like that doesn't have anything to do
Speaker 2: with the people sick with encephalitis at the hospital. Plus
Speaker 2: we already have an answer.
Speaker 4: I just it's a lot of times erin on this podcast,
Speaker 4: we have stories like that from like the eighteen hundreds
Speaker 4: where you look back and you're like, it was so obvious,
Speaker 4: how did you not see it? And like this was
Speaker 4: nineteen ninety nine. So it feels painful.
Speaker 2: It does, and yeah, and it's it's also just kind
Speaker 2: of like I think the aspect of the bureaucracy is frustrating.
Speaker 4: Oh my gosh. Yeah.
Speaker 2: So yeah, But doctor McNamara didn let that stand in
Speaker 2: her way her rejection from by the CDC, so she
Speaker 2: sought out some colleagues in the army. I'd asked them
Speaker 2: to test her samples. Awesome, and they did, and what
Speaker 2: they found was not Saint Louis encephalitis virus, but rather
Speaker 2: a virus that hadn't ever been detected in North America before,
Speaker 2: of course.
Speaker 4: West Nile virus West now virus.
Speaker 2: Suddenly the CDC became interested and stopped screening doctor McNamara's calls,
Speaker 2: just kidding. They re examined the samples from doctor Asna's patients,
Speaker 2: and sure enough West nolvirus.
Speaker 4: Yeah, so it's not surprising that it cross reacted.
Speaker 2: Oh yeah, not at all. That's like, I think that's
Speaker 2: a very reasonable thing for to happen. I guess, yeah,
Speaker 2: And so I'm not one hundred percent clear on the timeline,
Speaker 2: but I did watch an interview with doctor McNamara where
Speaker 2: she estimated that there was about a two or two
Speaker 2: and a half month delay resulting from the CDC not
Speaker 2: testing her samples. And so it's a couple of months
Speaker 2: where public health departments and wildlife health researchers could have
Speaker 2: gotten ahead of this virus and like to try to
Speaker 2: begin awareness campaigns and control efforts. And I think that,
Speaker 2: you know, one of the biggest lessons is that this
Speaker 2: nineteen ninety nine West Nile virus outbreak revealed how siloed
Speaker 2: we were, and in many ways still are in terms
Speaker 2: of monitoring the links between human, wildlife and environmental health.
Speaker 4: I feel like that's something we just touched upon in
Speaker 4: our anthrax episode.
Speaker 2: It absolutely is like what good is a canary or
Speaker 2: crow in the coal mine if you ignore it when
Speaker 2: it signals danger, or if you can't figure out what
Speaker 2: that danger is because you lack the diagnostic tools. This
Speaker 2: initial outbreak of westnyle virus in New York involved and
Speaker 2: estimated eighty two hundred human infections, eighty percent of which
Speaker 2: were asymptomatic, and the remaining twenty percent were mostly those
Speaker 2: with mild febrile illness, and then less than one percent
Speaker 2: develop this neuroinvasive disease. But in terms of confirmed cases,
Speaker 2: those numbers were a lot lower, sixty two cases I think,
Speaker 2: in seven deaths something around there.
Speaker 4: Very well.
Speaker 2: Yeah, the nineteen ninety nine outbreak in New York City
Speaker 2: was not an isolated event. It continued on to New
Speaker 2: Jersey and then to Connecticut, and it seemed likely that it.
Speaker 4: Was here to stay.
Speaker 2: The National surveillance program ARBONNET was created by the CDC
Speaker 2: and state health departments to monitor bird and human disease
Speaker 2: to be on the lookout for potential outbreaks of arboviral
Speaker 2: disease like West Nile, and one good indicator of an
Speaker 2: upcoming outbreak is the die off of birds preceding the
Speaker 2: emergence of West Nile virus in an area. And that's
Speaker 2: exactly what happened in two thousand and two in the
Speaker 2: huge epidemic of West Nile in North America, reaching all
Speaker 2: the way to Montana and Texas and as far north
Speaker 2: as Quebec and Ontario. And this dwarfed the nineteen ninety
Speaker 2: nine outbreak in New York with over forty one hundred
Speaker 2: confirmed cases of the disease and two hundred and eighty
Speaker 2: four deaths, and I don't know how many estimated infections,
Speaker 2: but with a lot of the cases of severe disease
Speaker 2: and just general illness happening in the midwest US, so
Speaker 2: like it had kind.
Speaker 4: Of shifted its distribution.
Speaker 2: In the period of just a couple of years, this
Speaker 2: virus had traveled incredible distances, but we still don't know
Speaker 2: exactly how it got to the US. It's possible that
Speaker 2: it was introduced from Israel, but the mechanism is unclear
Speaker 2: and we may never know for sure. But in the
Speaker 2: time since these epidemics, we have learned a lot about
Speaker 2: the virus and its ecology. We've learned that horses can
Speaker 2: become sick with the virus. We've learned that it can
Speaker 2: be transmitted through blood transfusions and organ transplantation through the
Speaker 2: placenta and breast milk. Environmental conditions are hugely important, like
Speaker 2: warmer temperatures mean a shorter time from infection to infectiousness
Speaker 2: in the mosquito, and they can also increase viral replication
Speaker 2: within those mosquitoes. So in cool weather, the mosquito has
Speaker 2: to live a longer time and in order to pass
Speaker 2: on the virus to humans, so it has to live
Speaker 2: longer to become infectious after feeding on the infected bird.
Speaker 2: Average rainfall years seem to provide suitable conditions or the
Speaker 2: best conditions for mosquito proliferation. Warm winters mean more mosquitoes
Speaker 2: survive over winter. All of these bits of information are
Speaker 2: like pieces of the West Nile virus puzzle.
Speaker 3: The more we gather, the more we.
Speaker 2: Can fit them together to get a better picture of
Speaker 2: why outbreaks happen, where and when they happen, the role
Speaker 2: that different bird species play in transmission, and how things
Speaker 2: like climate change and land use change may alter the
Speaker 2: landscape of disease risks.
Speaker 3: For this virus.
Speaker 2: And we are so excited to bring on a special
Speaker 2: guest to help us with a huge chunk of this
Speaker 2: West Nile virus puzzle. Yes, we told you it was coming,
Speaker 2: uh huh, And that is the bird part of the puzzle.
Speaker 2: We'll let her introduce herself right after this break and
Speaker 2: then after that, Aaron, I want to hear more about
Speaker 2: like West Nile virus in the world today.
Speaker 4: And I want to tell you about it.
Speaker 6: My name is Sarah Wheeler and I'm currently the biologist
Speaker 6: at Sacramento Yolo Mosquito.
Speaker 5: And Vector Control District.
Speaker 6: And at the district, I am now focused on applied
Speaker 6: research into mosquito control. But I started my journey on
Speaker 6: this path as an ornithologist and I've spent a lot
Speaker 6: of time investigating the role of wild birds and the
Speaker 6: spread of West now virus, the spread, amplification and maintenance
Speaker 6: of West now really and so I'm happy to talk
Speaker 6: some more about that today.
Speaker 2: Awesome, thank you so much for taking the time to chat.
Speaker 2: I just kind of want to start off by talking
Speaker 2: about the effects of Westnile virus on birds. So in
Speaker 2: this episode so far we have talked about the range
Speaker 2: of effects that westnle virus has had on humans, things
Speaker 2: like asymptomatic or mild disease all the way to these
Speaker 2: severe neurological complications or even death. So can you talk
Speaker 2: a bit about what infection looks like in birds and
Speaker 2: is there a similar wide clinical range of symptoms.
Speaker 6: There's absolutely a wide range of symptoms, and it can
Speaker 6: go from completely asymptomatic in some species or individuals, to
Speaker 6: debilitating to the point where the animal can't survive on
Speaker 6: its own, to completely fatal infections, and a lot of
Speaker 6: this can be somewhat generalized by the species. So we
Speaker 6: know that some species are more susceptible to westnil virus,
Speaker 6: So generally we think of passerines or songbirds being more
Speaker 6: susceptible to westnilvirus. But that is a huge range of
Speaker 6: bird species, and even within the range of songbirds, some
Speaker 6: are more refractory than others. And so for a bird
Speaker 6: that is going to deal with an infection, find you
Speaker 6: will never even know that they're infected. They might have
Speaker 6: a couple of days of virhemia or no viremia. That's
Speaker 6: virus circulating in the blood of the bird to the
Speaker 6: point where they could infect mosquitoes. They might not infect
Speaker 6: mosquitoes at all and not really become sick.
Speaker 5: To a bird that produces, you know.
Speaker 6: So much virus in its blood that it could infect
Speaker 6: any mosquito that feeds on it and it succumbs within
Speaker 6: four or five days.
Speaker 5: So yeah, it's a really wide range.
Speaker 2: Okay, So in the ones that are like severely impacted,
Speaker 2: what are some of the symptoms that they show.
Speaker 5: Yeah, so outward symptoms.
Speaker 6: If you see a bird with West nile, it might
Speaker 6: be kind of hunched and puffy looking.
Speaker 5: So we were doing some work with house.
Speaker 6: Finches and Westnoile virus and it turned out that they
Speaker 6: were sitting there just looking very puffed up, and that's
Speaker 6: a common symptom and a bird that's sick. And those
Speaker 6: birds actually had really low body temperature, so I think
Speaker 6: that it was having a hard time dealing with the
Speaker 6: infection and having trouble them regulating. Some birds develop acute
Speaker 6: neurological symptoms, so they get tremors or headpilts. So I
Speaker 6: think that sometimes birds that are in the transition period
Speaker 6: of just becoming very sick can actually just start acting weird.
Speaker 6: So we're studying the fatality events of crows in Davis, California,
Speaker 6: and it turned out that many of the crows that
Speaker 6: died of trauma actually were infected with West nile. So,
Speaker 6: I mean, a crow doesn't usually just get hit by
Speaker 6: a car, but if it's not feeling well, it might not.
Speaker 5: Get out of that gutter. Birds like raptors.
Speaker 6: Can actually develop ocular lesions, which means that they can
Speaker 6: clear the infection, but then they turn up at wildlife
Speaker 6: care centers or body condition because they can't hunt for themselves, right.
Speaker 2: So it's not necessarily that a lot of birds are
Speaker 2: dying outright, or maybe some birds are dying outright from
Speaker 2: infect but others are dying as a consequence of infection
Speaker 2: simply because they can't, like you said.
Speaker 3: Exist on their own or survive on their own anymore.
Speaker 5: It's affected their fitness.
Speaker 2: Wow, Okay, very interesting. And so you know, as you mentioned,
Speaker 2: there are some birds that seem to be more susceptible
Speaker 2: to West malavirus infection than others. Do we know anything
Speaker 2: about the reasons for these differences in susceptibility?
Speaker 6: Know what I really wish I knew this because it's
Speaker 6: it is a wide range, and like I said before,
Speaker 6: we think of it as being you know, taxa based,
Speaker 6: So crows birds in the crow family, so crows, jays,
Speaker 6: magpies are for the most part exquisitely sensitive to Westnow virus.
Speaker 6: They're very common dead bird programs. They you know, have
Speaker 6: higher mortality when exposed.
Speaker 5: They don't all die.
Speaker 6: We don't have a lot of evidence of crows surviving
Speaker 6: west now, but we definitely have antibody positive js and magpies.
Speaker 6: This does happen, so they via the infection, they produce antibodies,
Speaker 6: and that's something that we can detect in different cero surveys.
Speaker 6: But birds like pigeons, chickens. Chickens are actually really common
Speaker 6: sentinel birds for west Now virus surveillance. So we put
Speaker 6: them out in flocks and we bleed them every two
Speaker 6: weeks and see if they develop antibodies to west Now virus.
Speaker 6: And this was a really classic way for doing rbavirus surveillance,
Speaker 6: especially before you had PCR. You could put your chickens
Speaker 6: out and errology techniques have developed before PCR technique, so
Speaker 6: this was a really handy way of doing surveillance and
Speaker 6: chickens show no sign of infection. They don't infect mosquitoes.
Speaker 6: It's a total dead end post. So what is different
Speaker 6: between a chicken and a crow. I don't think we
Speaker 6: understand this, but there's something different. Whether or not it's
Speaker 6: some sort of pathogen effect where the virus is just
Speaker 6: not replicating as efficiently, or if it's at the bird
Speaker 6: is fighting it off more effectively, I don't.
Speaker 5: I don't think we know that.
Speaker 3: Yeah. Interesting.
Speaker 2: So a follow up question about susceptibility in birds with
Speaker 2: West Nile is about geography. So are there any patterns
Speaker 2: geographically in terms of susceptibility, Like are there do there
Speaker 2: tend to be more resistant birds in places where the
Speaker 2: virus has been circulating for you know, a really long time,
Speaker 2: like I'm talking on the scale of hundreds or thousands
Speaker 2: of years, versus places where the virus has been introduced
Speaker 2: more recently, such as in North America.
Speaker 5: I think that that is plausible.
Speaker 6: I mean, we don't see the mortality events where you know,
Speaker 6: west now virus first evolved that we see in North America.
Speaker 6: So our birds in North America are living with west
Speaker 6: now currently, like multiple generations have now been living with
Speaker 6: West Now and I don't know if we'll ever get
Speaker 6: to completely asymptomatic, but it's plausible to say that. But
Speaker 6: what that might look like in North America is an
Speaker 6: open question because it's not a static system. So how
Speaker 6: a bird deals with an infection, If it's able to
Speaker 6: fight that infection off and not develop as strong as
Speaker 6: a virehemia, then that would push the virus to being
Speaker 6: more virulent. So there's always that post pathogen interaction. And
Speaker 6: so West Nile, compared to other arboviruses in North America,
Speaker 6: has tended to be more virulent, and we thought that this,
Speaker 6: you know, helped to drive it into more refractory mosquito species.
Speaker 6: So it took a higher virehemia in order to get
Speaker 6: our native mosquitoes infected, and so that's kind of helped
Speaker 6: drive the system. And just over twenty years of West
Speaker 6: Nile virus, I think that we've seen some species that
Speaker 6: felt like they were getting more refractory, and it might
Speaker 6: be happening, but I don't know that we know that
Speaker 6: for sure. But West now virus transmission is not constant,
Speaker 6: it's not constant pressure, So you know a population that's
Speaker 6: under constant pressure might get a lot of west Now
Speaker 6: exposure for multiple years, and then we have two years
Speaker 6: of not a lot of west Now pressure, which allows
Speaker 6: that population to build back up.
Speaker 5: Perhaps you have.
Speaker 6: More open niches and more you know, nesting success, and
Speaker 6: so it allows populations to recover somewhat.
Speaker 2: Yeah, that's that's really fascinating. You do have to consider
Speaker 2: all the different components of the system and the cycle
Speaker 2: that it's not just about the bird and the virus.
Speaker 2: It's also about the mosquito and the bird and the
Speaker 2: virus and all of these moving parts that are difficult
Speaker 2: so sometimes get a handle on.
Speaker 6: Yeah, I mean the mosquito is a huge part of
Speaker 6: this whole situation. Like mosquito is in a way like
Speaker 6: the driving force of the whole transmission cycle. Because the
Speaker 6: mosquitoes that transmit west now would almost like nine times
Speaker 6: out of ten, prefer to feed.
Speaker 5: On a bird, so qelex. They really like to feed
Speaker 5: on birds. They prefer birds.
Speaker 6: So if you look at blood meal I d studies
Speaker 6: where people collect blood fed cuelex and you look at
Speaker 6: the DNA and the blood meal and identify what they
Speaker 6: fed on, you'll generally.
Speaker 5: See a bird species there.
Speaker 6: Even though nine times out of ten that QLX mosquito
Speaker 6: is going to feed on a bird.
Speaker 5: If a human is sitting out.
Speaker 6: There, you know, barbecuing or making it easy for the mosquito,
Speaker 6: the mosquito might just take advantage of that. So that's
Speaker 6: why it's predominantly a bird mosquito cycle, because the mosquitoes
Speaker 6: are predominantly feeding on the birds. The birds are the
Speaker 6: amplifying posts, and that's kind of how it cycles, with it,
Speaker 6: you know, occasionally spilling over into humans or horses. And
Speaker 6: I get the question a lot, like what about my
Speaker 6: dog or my cat, you know, and I think, I'm
Speaker 6: sure that they're bitten by infected mosquitoes, but we don't
Speaker 6: see any kind of reports of infection and cats, so
Speaker 6: probably just another dead end host.
Speaker 2: I'm like now brimming with a bunch of questions about
Speaker 2: mosquitoes and mosquito ecology and so is it really just
Speaker 2: sort of availability and opportunity of you know, whatever hosts
Speaker 2: are there for the mosquitoes, or do these tend to
Speaker 2: be more sylvatic species, like do they hang out mostly
Speaker 2: in wooded areas or are they also urban species? You know,
Speaker 2: what are some of those differences among competent mosquito species.
Speaker 6: So in our area, the two main vectors of western
Speaker 6: alvirus are kee Wex pipions and Keelex tarsalis.
Speaker 5: QX tarsalis tends.
Speaker 6: To breed more in rural areas, so in our area
Speaker 6: they breed really heavily in the rice fields that surround
Speaker 6: our urban centers. But Keelex pipions is totally an urban breeder.
Speaker 6: They love catch basins, So in your gutter, there's that
Speaker 6: little grate and there's like a little cement compartment down
Speaker 6: there that is supposed to catch the debris before it
Speaker 6: flows out the creek or whatever. Well, those almost all
Speaker 6: hold water, and so HeLEX pipians can really take advantage
Speaker 6: of that. A bucket of water in your backyard or
Speaker 6: you know, a green swimming pool or any source that they.
Speaker 5: Can take advantage of, and those happen quite.
Speaker 6: Regularly in urban areas, so you can definitely have both
Speaker 6: urban and rural transmission of wesnou virus. So sometimes in
Speaker 6: urban areas you have a concentration of very competent amplifying hosts.
Speaker 6: So in the city you see a lot of crows,
Speaker 6: you see a lot of jays, you see house finches,
Speaker 6: house sparrows, and all these species are competent amplifying hosts,
Speaker 6: and then you also have the mosquito, So you have
Speaker 6: a concentration of players that can contribute to an amplification cycle.
Speaker 6: When you get out into rural areas, you also have
Speaker 6: competent amplifying hosts out there, and great the tarsalus is
Speaker 6: out there. Sometimes you even have pippians and rural species.
Speaker 6: But you might have an introduction of more species, and
Speaker 6: sometimes the addition of greater species variety can have a
Speaker 6: diluting effect on effective transmission. So if you have a
Speaker 6: range of possible hosts and you know fifty percent of
Speaker 6: them are great amplifying hosts, that's going to lead to
Speaker 6: a different transmission cycle than a scenario where twenty five
Speaker 6: percent of them are great amplifying hosts. So that's why
Speaker 6: a lot of times you've seen West now be a
Speaker 6: little bit more urban in nature. I mean, it does
Speaker 6: happen rurally, absolutely, But.
Speaker 2: Yeah, So before I shift to talking about sort of
Speaker 2: more of the role that birds play in the transmission
Speaker 2: cycle of West malavirus, I want to just ask this,
Speaker 2: you know, overall question about the impact that West Nile
Speaker 2: virus has had on bird populations in North America since
Speaker 2: it's been introduced, and I'm sure that it's not consistent
Speaker 2: across the board, but have we seen substantial declines in
Speaker 2: some species and no impact on others.
Speaker 5: Yeah.
Speaker 6: So, especially when West Nile was tearing across the US
Speaker 6: and there was huge bird die offs across the US,
Speaker 6: a lot of people were very concerned about different bird species,
Speaker 6: like zoo collections were even getting hit, and you know,
Speaker 6: precious animals that you know might be sensitive or in decline, like,
Speaker 6: there was a lot of concern about what West Snow
Speaker 6: would do to those burd communities.
Speaker 5: And so myself and other.
Speaker 6: Researchers have spent some time trying to figure out what
Speaker 6: the impact of West Nile has been on these bird communities.
Speaker 5: And the kind of data that.
Speaker 6: You usually use for these kinds of analysis are some
Speaker 6: of these big bird census databases. So the Christmas Bird
Speaker 6: Count or the Breeding Bird Survey can kind of help
Speaker 6: you understand impacts on bird communities because they've been in
Speaker 6: place for a long time before West Nile even got here,
Speaker 6: and so you can look at the impact on those
Speaker 6: bird communities after west Now and see if there's been
Speaker 6: any kind of changes in their population dynamics. It's not perfect, right,
Speaker 6: There's other things that affect birds than West Nile. And
Speaker 6: I would say, especially like within the first five years,
Speaker 6: there are species that absolutely saw declines like there are
Speaker 6: there were declines. So a bird in our area of
Speaker 6: the yellow bill magpie, it's a bird that's only found
Speaker 6: in the central Valley of California, Like a huge part
Speaker 6: of its population was under West Nile virus pressure. Like
Speaker 6: you could see clear declines in that bird. They're kind
Speaker 6: of noisy birds. They're like a big black and white
Speaker 6: bird with a yellow bill, Like you notice them right. Anecdotally,
Speaker 6: people were saying, yeah, all of a sudden, the magpies
Speaker 6: were just gone.
Speaker 5: Well, you know, they.
Speaker 6: By their own nature probably helped preserve themselves a bit
Speaker 6: because not only can yellow bill magpiesself be somewhat nomadic
Speaker 6: in nature, like West Snile does not exert even pressure
Speaker 6: every year, and I think that that was what really
Speaker 6: allowed them to kind of level out and you know,
Speaker 6: get back on a better track with their population. So
Speaker 6: that you know, when West Nole first came in, like
Speaker 6: we had a multiple heavy years of pretty steady transmission
Speaker 6: and now it's like from year to year it's like, oh,
Speaker 6: it's a big year for Sacramento and it's not a
Speaker 6: big year for San Joaquin, and so it moves around,
Speaker 6: so it's not exerting that constant pressure.
Speaker 5: On that bird population.
Speaker 6: Crows definitely have had some impact, like they're the most sensitive.
Speaker 5: They're just exquisitely sensitive.
Speaker 6: But the odd thing about crows, and this isn't somewhat
Speaker 6: of a sidebar, they're always underrepresented in mosquito blood meal
Speaker 6: ID studies. So you're like, well, why we have all
Speaker 6: these dead crows if mosquitoes aren't them, And so that,
Speaker 6: I mean that may be a function of just how
Speaker 6: a crow lives its life or how those blood philip
Speaker 6: fed mosquitoes are collected.
Speaker 5: But yeah, I mean I think that West Nile has
Speaker 5: a huge impact on those species.
Speaker 2: Yeah, I had heard that about crows, But I think
Speaker 2: that's really curious about the lack of representation in the
Speaker 2: mosquito blood samples.
Speaker 4: Hmm.
Speaker 6: Yeah, that's a big story right there. And so it's
Speaker 6: been a source of debate about why we don't see
Speaker 6: them represented in bloodmulated idease days and is it that
Speaker 6: they're not really an important amplifying host despite the fact
Speaker 6: that they're like exquisitely sensitive to West Nile virus.
Speaker 5: And of the birds that.
Speaker 6: You have been investigated for their response to West Nile infection,
Speaker 6: their viremias are like some of the highest right, so
Speaker 6: they produce like the most virus in their blood. Makes
Speaker 6: them extremely competent amplifying hosts. So it's like, are they
Speaker 6: not important amplifying hosts with all this virus and a crow,
Speaker 6: especially if they'll sit there moribund for like two or
Speaker 6: three days before they actually succumb to infection, so they
Speaker 6: could just infect any mosquito that comes by to feed
Speaker 6: on them. And so, but when you do these blood
Speaker 6: meal I these studies, you find a lot of pigeons,
Speaker 6: you find doves, you find robins, you find a lot
Speaker 6: of other species like housewinches, And you're like, well, that
Speaker 6: leads me to believe that they're more important because that's
Speaker 6: what mosquitoes are feeding on.
Speaker 3: That is so interesting.
Speaker 2: Yeah, And so it's not as cut and dry as
Speaker 2: the birds that are the most susceptible and most abundant
Speaker 2: in a community or in an area are the ones
Speaker 2: that are going to play the biggest role in transmission
Speaker 2: or risk of exposure to humans, So are there these
Speaker 2: other ecological characteristics or certain species that do play a
Speaker 2: role as these reservoir hosts.
Speaker 5: So I feel like.
Speaker 6: I used to see this more clearly than I see
Speaker 6: it now.
Speaker 5: So I think that.
Speaker 6: Before we had a lot more information, we had, you know,
Speaker 6: some good baseline data on what types of virenias different
Speaker 6: species of birds kind of produced. So basically, the higher
Speaker 6: the virenia, the more likely that a greater number of
Speaker 6: mosquitoes will be infected to the point where they will
Speaker 6: then be able to transmit. So that is on itself
Speaker 6: a spectrum. So a mosquito needs to be able to
Speaker 6: take enough virus from the bird in order for it
Speaker 6: to become infected the point where then it can transmit.
Speaker 6: So birds that produce higher virenias ultimately infect more mosquitoes
Speaker 6: that can then themselves transmit. I used to think, okay,
Speaker 6: like pigeons, and they're not great amplifying hosts. Crows, jays, magpies,
Speaker 6: house pinches, house sparrows. These tend to be you know,
Speaker 6: pretty good amplifying hosts, especially the corvids. But it's it's like,
Speaker 6: once you get out of the box of looking at
Speaker 6: a figure on a paper of what's known about different
Speaker 6: viroemia profiles for different birds, Like it is a whole assemblage,
Speaker 6: it's a community of birds, and you know that even
Speaker 6: like though there's certain patterns that are followed for a
Speaker 6: given species, individual to individual are going to vary at
Speaker 6: this point. I mean, we never even used to test
Speaker 6: morning doves as a part of our dead bird surveillance
Speaker 6: program because it was like, well, they're not great amplifiers,
Speaker 6: so we don't even really need to look at them
Speaker 6: because chances are that they've died.
Speaker 5: Of something else.
Speaker 6: Well, on a whim, we decided to well, let's just
Speaker 6: test this. And it turns out that no, this species
Speaker 6: that's pretty much refractory to westnow virus infection can act
Speaker 6: actually still die of West Nile or it can die
Speaker 6: with a high amount of virus in its blood and tissues.
Speaker 6: Which you would think then, is that it actually succumbed
Speaker 6: to infection. Maybe it didn't, but it had a high
Speaker 6: amount of virus in its tissues. So it's created like
Speaker 6: less steady ground for assertions that I would have made
Speaker 6: in the past, like oh, they're not really playing a
Speaker 6: role if you have much a doves and maybe that
Speaker 6: would not be like a community that would produce as
Speaker 6: much virus as you would think it if there were
Speaker 6: more crows and j's and things like that around. So
Speaker 6: when you look at an area, there could be two
Speaker 6: hundred species in that area. Some of them will maybe
Speaker 6: never amplify a west Nile. But once you take that
Speaker 6: scale of birds and run it all the way up
Speaker 6: to say a crow is the most susceptible in a community,
Speaker 6: it's going to be a spectrum, right, It's a spectrum.
Speaker 6: And so as far as do certain assemblages of birds
Speaker 6: create a more risky west now virus scenario, I think
Speaker 6: that from a very high level view, urban areas tend
Speaker 6: to create assemblages of birds that can, you know, lead
Speaker 6: to amplifying events.
Speaker 5: But it's not ever the bird that is dangerous to people.
Speaker 5: It's the mosquito.
Speaker 6: Right, So people don't have to worry about protecting themselves
Speaker 6: from the birds. They have to protect themselves from the mosquito.
Speaker 6: And so that's why we really when we think about risk,
Speaker 6: we think about mosquitoes.
Speaker 5: And so we think.
Speaker 6: About, well, how many mosquitoes are in this area, like
Speaker 6: what proportion of them are infected with west now virus?
Speaker 6: Like what can we do to interrupt that transmission cycle
Speaker 6: because it's easier to deal with it and focus on
Speaker 6: the mosquito and it's the more direct link to exposure. Yes,
Speaker 6: bird community matter, it matters, but it's it's variable and
Speaker 6: it's hard to absolutely state what's the best amplifying community.
Speaker 2: You know, right, Ultimately it comes down to the mosquito
Speaker 2: and how many mosquitoes there are in a certain environment
Speaker 2: and how often humans are out and so on.
Speaker 3: Yeah.
Speaker 2: Absolutely, So let's talk a bit about bird migration. So
Speaker 2: we know that bird migration has an impact on potentially
Speaker 2: the geographic spread of West Nile virus and potentially other
Speaker 2: you know, bird associated pathogens. But how do things like
Speaker 2: the stress of migration impact bird communities or you know,
Speaker 2: the immune systems of birds and making them more susceptible
Speaker 2: potentially to West Nile virus.
Speaker 6: Yeah, so migration has been definitely a thing that we've
Speaker 6: spent a lot of time thinking about. So there is
Speaker 6: a somewhat of a mystery with West Nile and that's
Speaker 6: where it does go in the winter. So overwintering mechanisms
Speaker 6: for Westnile virus are not well understood. It was always
Speaker 6: a possibility that West snile was overwintering, you know, down
Speaker 6: somewhere where it's warmer where you could have year round
Speaker 6: transmission and then reintroduction events were kind of by migrating
Speaker 6: birds bringing it into new areas every year, and maybe
Speaker 6: that could attribute to why we see it flare up
Speaker 6: in different places from year to year. Looking at the
Speaker 6: genetics of the virus, this is not really supported, but
Speaker 6: we did spend a.
Speaker 5: Lot of time looking at migratory birds to kind of
Speaker 5: figure out if they were spreading the virus around.
Speaker 6: At some point I was down at the Coachella Valley,
Speaker 6: like along the Sultan Sea, and every year we would
Speaker 6: go down there to collect as many migratory birds as
Speaker 6: we possibly can and collect a small blood sample and
Speaker 6: test that blood sample for both antibodies and.
Speaker 5: Viral particles.
Speaker 6: Basically, does the has this bird been exposed to West
Speaker 6: Nile and is it currently infected. So it's a long
Speaker 6: shot looking for a virehemia, especially in a migrating bird,
Speaker 6: because migration is a very costly event.
Speaker 5: For those birds.
Speaker 6: So for them to be able to be fit enough
Speaker 6: to migrate while acutely infected.
Speaker 5: Is I don't know if that's possible.
Speaker 6: It may be I mean, birds are amazing it could
Speaker 6: they could do it, especially for short hops, maybe like
Speaker 6: from one stop to the next, they might get infected
Speaker 6: and then be able to carry it to.
Speaker 5: The next hop.
Speaker 6: And then if it's a species that's so refractory to
Speaker 6: West Nile that it's able to migrate in an infected state, like,
Speaker 6: how is that going.
Speaker 5: To play a role in a transmission events.
Speaker 6: So there have been other researchers that have found some
Speaker 6: kind of indication of birds migrating wall infected. So I'm
Speaker 6: sure it happens, But when we looked at the data
Speaker 6: for the birds coming in and the birds that were here,
Speaker 6: it just really seemed like the majority of the infection
Speaker 6: was happening here. So when we did find migrants that
Speaker 6: were infected with West Nile virus, they were heading back
Speaker 6: down south. They weren't heading north. They had been here
Speaker 6: all summer and were heading back down to their Central
Speaker 6: American overwintering grounds, and they had already been exposed. And
Speaker 6: so it really seemed like it wasn't migratory birds that
Speaker 6: were constantly receding infection just by what we were observing
Speaker 6: with you know, Westnile virus activity in the birds that
Speaker 6: it seemed like there was something that was overwintering locally
Speaker 6: and flaring up, and then as migrants were coming through,
Speaker 6: there was always the potential that they could be exposed
Speaker 6: and then hop it to the next location.
Speaker 3: That is very interesting.
Speaker 2: It kind of turns a bit like on the narrative
Speaker 2: that is so like, oh, well, you know birds that
Speaker 2: move from one place to another, and it makes it so.
Speaker 3: Easy for it to spread.
Speaker 2: It might not necessarily be why we see, you know,
Speaker 2: these events happening, and so on that note about how
Speaker 2: long or is there any sort of window during which
Speaker 2: in an infection there is circulating virus in the birds
Speaker 2: that are susceptible.
Speaker 4: And do seem to have like this vireemia.
Speaker 2: Is there a length of time during which you can
Speaker 2: collect virus.
Speaker 6: So if you're looking at a bird who's just been infected,
Speaker 6: by about two days you can detect virus in the blood,
Speaker 6: and then by about seven days, if it's not cleared,
Speaker 6: it's most likely not going to survive, okay.
Speaker 2: And then is there you know, lasting immunity following or
Speaker 2: can a bird get reinfected?
Speaker 5: It seems to be lasting community.
Speaker 4: Okay.
Speaker 2: So, as someone who works in the applied you know
Speaker 2: side of things and has this research background as well.
Speaker 2: What do you see as the biggest challenges to West
Speaker 2: nolevirus control?
Speaker 6: Honestly, for West nolevirus, we have to be able to
Speaker 6: have good effective surveillance methods. We have to have effective
Speaker 6: mosquito control tools, and so thankfully we've gotten a very
Speaker 6: efficient system for how mosquitoes are trapped and how they're tested.
Speaker 6: These are kind of pretty well worked out. But at
Speaker 6: this point in mosquito control, there are two active ingredients
Speaker 6: that are used for controlling mosquitos. So you have pyriethrins
Speaker 6: and pyreethroids, and you have organophosphates.
Speaker 5: So these are the insecticide classes and they're.
Speaker 6: Used in many many other fields, common in agriculture. They're
Speaker 6: common like if that pest control guy comes by your house,
Speaker 6: it's like, oh, you know, you have spiders all over
Speaker 6: I could spray for that. Well, they're spraying, but we're spraying.
Speaker 6: And so insecticide resistance is the growing problem and so
Speaker 6: as we move forward, we're going to have we're going
Speaker 6: to have to find creative solutions for how to break
Speaker 6: that transmission cycle through effective mosquito control. And this will
Speaker 6: continue to be a problem moving forward because I mean,
Speaker 6: mosquito control is a small slice of the you know,
Speaker 6: insecticide usage pie especially public health mosquito control like applications.
Speaker 6: So there aren't generally products designed especially for mosquito control
Speaker 6: because it's like it's not the largest market. You know,
Speaker 6: there are innovations that are coming out. So for a
Speaker 6: species eighties of gypty, which is a terrible vector around
Speaker 6: the world, spreads dangi and.
Speaker 5: Zika and chinkgunya.
Speaker 6: It's been invasive in a lot of areas of California.
Speaker 6: So we're now dealing with the gippi in California and
Speaker 6: throughout California. And so there's a lot of talk now
Speaker 6: about well, can we you know, use sterile insect programs to.
Speaker 5: Control these mosquitoes.
Speaker 6: And I think that that that's being used more and more,
Speaker 6: like it's it's still an emerging option and it might
Speaker 6: not be like what we can use for qlex control,
Speaker 6: but it's an example of thinking of new solutions to
Speaker 6: old problems. And I think that that's what we're going
Speaker 6: to have to continue to do moving forward, is think
Speaker 6: outside the box and you know, push the envelope.
Speaker 4: Thank you so much. That was Awesome. We knew that
Speaker 4: we were missing such a big part.
Speaker 7: I mean, I learned a lot, so much, so tell
Speaker 7: me more. Let's hear even more. So we'll just now
Speaker 7: focus on west now virus mostly in humans and look at.
Speaker 4: The big picture. Shall we focusing first on North America,
Speaker 4: since that's where we ended your section erin. Since west
Speaker 4: now virus made its debut in New York in nineteen
Speaker 4: ninety nine, the virus has resulted in over forty eight
Speaker 4: thousand reported cases in the US, twenty four thousand of
Speaker 4: those have been neuroinvasive, and it has resulted in over
Speaker 4: twenty three hundred deaths.
Speaker 2: Wow.
Speaker 4: Yeah in about twenty years now. It's estimated that the
Speaker 4: true number of infections is over seven million human infections
Speaker 4: in the continental United States. Wow. Wow, I just got it.
Speaker 4: Can just keep saying wow, That's all we can say.
Speaker 4: It's by far one of the most important zoanotic diseases
Speaker 4: and one of the most important causes of viral especially
Speaker 4: vector born encephalitis in the US since its introduction, and
Speaker 4: like you said, Aaron, it has spread throughout the entire
Speaker 4: United States. It's present throughout all of North America, It's
Speaker 4: likely present in Central and South America as well, but
Speaker 4: we don't have great data on Central and South America.
Speaker 4: Whether that's because it's overshadowed by other infections that look similar,
Speaker 4: like maybe Dengey fever, or whether it's there but at
Speaker 4: very low levels, or it's just not being reported, we
Speaker 4: don't really know, but we don't have good data on it.
Speaker 4: But even within the US, while like over fifty percent
Speaker 4: of counties in the US have reported at least one
Speaker 4: case over the course of time, they're not evenly distributed.
Speaker 4: Like cases are not evenly distributed, and outbreaks tend to
Speaker 4: happen in like discrete areas that vary a lot year
Speaker 4: to year. So overall, the actual number of reported cases
Speaker 4: in the US since its introduction has been it varies
Speaker 4: a lot year to year, but it hasn't necessarily been
Speaker 4: steadily growing or anything like that. But you do see
Speaker 4: a lot of year to year variation and a lot
Speaker 4: of geographic variation, like one year you'll have a whole
Speaker 4: bunch in Montana and another year a whole bunch somewhere else,
Speaker 4: et cetera. And it's not just humans, of course. Westnlvirus
Speaker 4: is a substantial animal pathogen in the US. It's caused
Speaker 4: over twenty eight thousand cases in horses and mortality that
Speaker 4: we know of in over three hundred bird species, like
Speaker 4: we heard a lot about already. In Canada, over five
Speaker 4: thousand human infections have been reported, and across Europe, outbreaks
Speaker 4: happen almost every year, but the biggest outbreak, especially in
Speaker 4: Europe by far, was in twenty eighteen, when there were
Speaker 4: over fifteen hundred cases that were reported across Europe. That
Speaker 4: was over seven times as many cases as had been
Speaker 4: reported in the previous seven years. Dang, right, in one
Speaker 4: single year. And so whenever we see outbreaks like this
Speaker 4: that happen, like really big outbreaks all of a sudden,
Speaker 4: especially of a vector born disease, we have to think about, like,
Speaker 4: what are the factors environmentally that are impacting this? And
Speaker 4: Aarin you kind of touched on this a little bit,
Speaker 4: but we're going to get into it a little bit more.
Speaker 4: Oh yeah, and then of course we're going to talk
Speaker 4: about climate change. So, like many, if not all, of
Speaker 4: the vector born diseases that we've covered on this show,
Speaker 4: it's not entirely clear how climate change either is going
Speaker 4: to affect or has already begun to affect West Nile
Speaker 4: virus incidents, prevalence, and also distribution. But we can gather
Speaker 4: at least a little bit of information based on especially
Speaker 4: that twenty eighteen Europe outbreak as well as just what
Speaker 4: we know about the mosquito and the virus. So, given
Speaker 4: that West Nile virus is mostly transmitted by mosquitos in
Speaker 4: the genus Qlex, their natural ecology is such that in
Speaker 4: an increasingly warm climate, it's very likely that that type
Speaker 4: of climate will increase both the abundance of these mosquitoes
Speaker 4: as well as increase their overall distribution. And like you mentioned, Aaron,
Speaker 4: if they're better at harboring virus in warmer climates compared
Speaker 4: to colder climates where they're maybe not as good a vectors,
Speaker 4: that's important as well.
Speaker 2: Oh yeah, that's that's not good news.
Speaker 4: No, it's really not. And that outbreak in Europe in
Speaker 4: twenty eighteen, it turns out that that year was not
Speaker 4: only one of the hottest years ever recorded, it was
Speaker 4: also a very very wet spring that was followed by
Speaker 4: a summer drought, which likely led to a very early
Speaker 4: expansion of the Qlex mosquitoes, which led to an increase
Speaker 4: in viral transmission. So what we saw that year was
Speaker 4: cases being reported earlier in the year than ever before,
Speaker 4: and then an outbreak that was the largest ever recorded,
Speaker 4: more cases like I said in the previous seven years,
Speaker 4: and over a larger geographic distribution than had been previously recorded.
Speaker 4: That year alone, cases were reported in Austria, Bulgaria, Croatia, Cyprus,
Speaker 4: Czech Republic, France, Greece, Hungary, Italy, Portugal, Romania, Serbia, Slavinia, Spain, Turkey, everywhere.
Speaker 3: Yeah.
Speaker 4: So, despite its global prevalence, despite it being such a
Speaker 4: common cause of mosquito born infection in the US for
Speaker 4: over twenty years, we still don't have any specific treatments,
Speaker 4: and we still don't have any licensed human vaccines.
Speaker 2: And with every year, I feel like becoming the hottest
Speaker 2: year on record.
Speaker 4: Right, yeah, every year, Yeah, year it feels like this one.
Speaker 4: There are at least four different animal vaccines, I think
Speaker 4: primarily for horses, and there have been Phase one and
Speaker 4: two studies of human vaccines, but there haven't been any
Speaker 4: Phase three or like the larger efficacy studies, And it
Speaker 4: seems mostly because there's not a market for it financially,
Speaker 4: which is so frustrating and what's even more frustrating is
Speaker 4: that we have vaccines for a lot of other flavaviruses
Speaker 4: like yellow fever virus. We have a vaccine Japanese and
Speaker 4: ccephalitis virus. We have a vaccine. Now. We even have
Speaker 4: a vaccine for Dengey virus. Apparently from a paper from
Speaker 4: twenty nineteen, there have been at least six different candidates
Speaker 4: of vaccines that have gone through these phase one and
Speaker 4: two trials. At least two of them seem to produce
Speaker 4: good immunity after a single dose, which is what would
Speaker 4: be needed for it to be a cost effective vaccine.
Speaker 4: None of the animal or the horse vaccines are single dose.
Speaker 4: They all require multiple doses as well as annual boosters.
Speaker 4: Oh okay, so, but there is at least promise, I think,
Speaker 4: both in terms of the immunology of West Nile virus
Speaker 4: and of flavaviruses in general, and then the fact that
Speaker 4: at least we have vaccines in phase one phase two trials.
Speaker 4: It seems to be kind of like a funding issue, etc.
Speaker 4: But in general, because of this lack of vaccine, control
Speaker 4: efforts really rely on prevention of infected mosquitos, So things
Speaker 4: like integrative pest management mosquito infection, like you mentioned, Aaron, sentinel,
Speaker 4: bird surveillance and all of that to try and reduce
Speaker 4: the prevalence of infected adult mosquitoes. And that, my friends,
Speaker 4: that's West Nile virus.
Speaker 3: That's West Nile virus.
Speaker 4: That was a fun one, Aaron. I learned a lot.
Speaker 2: Yeah, it was a really interesting one. I can't believe
Speaker 2: we hadn't done this yet.
Speaker 7: Hey, we did it now, We did it now. And yeah, sources, sources.
Speaker 7: I have a lot of papers I'm going to shout
Speaker 7: out just too, and one is by Savar from two
Speaker 7: thousand titled Westnile Virus and Historical Overview. And the other
Speaker 7: that I wanted to shout out for fun is by
Speaker 7: our PhD advisor, doctor Brian Allen.
Speaker 4: Yeah, yeay, and that is Alan at all.
Speaker 2: From two thousand and nine titled Ecological Correlates of Risk
Speaker 2: and Incidents of West Nile Virus in the United States.
Speaker 2: And I also watched, as I mentioned, several videos on
Speaker 2: West Nile virus and I will post a links to these.
Speaker 2: There were a couple ones that were especially helpful. West
Speaker 2: Nile Virus the first decade by Richard Ayler. One on
Speaker 2: PBS West Nyle outbreak in New York City and then
Speaker 2: also a great interview with Tracy McNamara and this video
Speaker 2: titled one Health and the Lessons Learned from the nineteen
Speaker 2: ninety nine West Snyle Outbreak, and that is by Microbe World.
Speaker 4: I also had a good number of papers a couple
Speaker 4: of my favorites for the overview of West Nile virus.
Speaker 4: We're both titled West Nile Virus one from the Lancet
Speaker 4: Neurology two thousand and seven and one from the Lancet
Speaker 4: Infectious Disease in two thousand and two. So kind of
Speaker 4: older papers but still really good. If you want more
Speaker 4: info on the development of vaccines, there was a paper
Speaker 4: called twenty years of Progress towards West Nile Virus Vaccine
Speaker 4: development in Viruses from twenty nineteen. And we'll post all
Speaker 4: of our sources from this episode and every one of
Speaker 4: our episodes on our website, This podcast will Kill You
Speaker 4: dot Com.
Speaker 2: We will thanks again so much to the amazing guests
Speaker 2: for this episode. We so appreciate you coming on to
Speaker 2: chat with us.
Speaker 4: Yeah, thank you. Thank you also to Bloodmobile, who provides
Speaker 4: the music for this episode and all of our episodes.
Speaker 2: And thank you to exactly Right, of whom we are
Speaker 2: a very proud member, and thank you to you listeners.
Speaker 4: We really love making this podcast, so thanks for listening
Speaker 4: to it.
Speaker 2: Yeah, and a special shout out also to our amazing,
Speaker 2: incredible supporters on Patreon.
Speaker 3: We love you.
Speaker 2: You're amazing, and everyone you only have a few more
Speaker 2: seconds to wait until your ears get to be blessed
Speaker 2: with the joyous sounds of mc Bugsy and West Nile Story.
Speaker 4: West Nile Story, Bring us out, Aaron, wash your hands.
Speaker 4: You've filthy animals.
Speaker 9: Who's heard of West Now pate it may not realize it,
Speaker 9: but it's inside of mosquitoes and they get credits of
Speaker 9: people to cover up rock rebell it, get rid of
Speaker 9: standing water. Mosquito bites can be more than just a bomb.
Speaker 9: No vaccine to protect, no medication to treat it. That
Speaker 9: means attention to prevention is the challenge. So me it empty, scrub,
Speaker 9: turn over, cover tip and toss out containing. Clean up
Speaker 9: the yard once a weaken your lippy, best life. Later
Speaker 9: long loose like colored clothes, so no skins exposed to
Speaker 9: biting mosquitoes. Attempting undercover pros use repellents to protect yourself
Speaker 9: and those that you love from the potential help gets
Speaker 9: of being bitten by a move who's heart a west
Speaker 9: Now virus. You may not real loize them. It's inside
Speaker 9: of mosquitoes and they get spreaddit to pieces, cover up rock,
Speaker 9: rebelling and ritt is standing water. Mosquito bites can mean
Speaker 9: more than just a vod yo who's herd a west
Speaker 9: Now virus. Cap may not realize them, but it's inside
Speaker 9: of mosquitoes and they get spread it to people, color
Speaker 9: up rock, repelling the GrITT is standing water. Mosquito bites
Speaker 9: can be more than just a bob west Now. There's
Speaker 9: arected public health in the summer time and here for
Speaker 9: twenty years shout out to Queen's ninety nine rapid spread
Speaker 9: from east to west. Now we're throughout the continental US
Speaker 9: qlex mosquito vector with the bird preference in nature, guests
Speaker 9: now cycles between mosquitoes and birds when those mosquitosquito people
Speaker 9: infections occur steady sipping dust till dawn because they're not
Speaker 9: time biders attack in twilight. Like micro vampire who's hurt
Speaker 9: a west Now virus may not realize them food it's
Speaker 9: inside of mosquitos and nicket spread it to people to
Speaker 9: color up rock repelling I finished standing water. Mosquito bites
Speaker 9: can be more than just a bottley who's hurt. A
Speaker 9: west Now virus can make a re alizza food. It's
Speaker 9: inside of mosquitoes and they get spreaded to people to cover.
Speaker 6: Up rock repelling.
Speaker 9: The frit is standing water, Mosquito bites can be boiled
Speaker 9: just a bottle now. Luckily, most folks effective will never
Speaker 9: feel sick, but somemost suffer from beaver rash, aches and weakness.
Speaker 9: The most recover completely. The fatigue can persists for weeks
Speaker 9: or months. You could be living lethargic and listless. Unfortunately,
Speaker 9: any age can get severe illness. Of people older than
Speaker 9: sixty and the sick of the highest risk of neuroin
Speaker 9: basic cases with lifelong effects except for light as men
Speaker 9: insitis from a virus that wrecks protect from west Now vibrus.
Speaker 9: Here's hoping you're realized side of mosquitoes and they get
Speaker 9: spreaded to people to cover up rock repelling. If frit
Speaker 9: is standing water, mosquito bites can be more than just
Speaker 9: a bomp. Just yourself representative control mosquito that never bites
Speaker 9: will never have the chance to change your life. Cover
Speaker 9: up and use EPA approved repellents. When mosquitoes are active,
Speaker 9: it's bugs in amount