Human Choices Reshape Ecosystems And Push Viruses Closer To Us

Social Norms And One Health Setup

SPEAKER_03 0:09

This is a podcast about One Health. The idea that the health of humans, animals, plants, and the environment that we all share are intrinsically linked. Coming to you from a team of scientists, physicians, and veterinarians, this is Infectious Science. Where enthusiasm for science is contagious. Hello everyone. Welcome back to this episode of Infectious Science. We are so excited to be here with you all today. I'm Camille, one of your co-hosts, and I'm joined by Christina and Alex. Say hi.

SPEAKER_06 0:41

Hey.

SPEAKER_03 0:43

It's good to be back, Camille. How are we doing today?

SPEAKER_06 0:47

Thank you so much for having us here.

SPEAKER_03 0:49

For having us here. You're on the team, man. We're so having you. You're just you're part of you're on the podcast. Thank you for being here.

SPEAKER_02 1:06

I'm a creature of habit and of etiquette. What can I say? I went to too many etiquette classes over the years. It was ingrained into me, you know?

SPEAKER_03 1:14

So was it Emily Post Etiquette? Have you ever seen those books in Barnes and Nobles or whatever? They're like massively thick books of etiquette that who has read? Yes.

SPEAKER_02 1:22

I bought a copy when I was 10. It's still on my bedside table.

SPEAKER_03 1:26

Have you read it cover to cover?

SPEAKER_02 1:28

Yes.

SPEAKER_03 1:31

I love that for you, Alex. That's wonderful. Your book tastes are so very different from mine. I appreciate that. Is it a dry read, though? Be honest. You could say it politely, but be honest. Is it a dry read?

SPEAKER_02 1:44

I personally thought that it was entertaining. I felt like there was a little bit of cattiness in there, a willingness to poke at just those who violate some of these societal norms. It was entertaining for me personally, but at the same time, you also have to bear in mind I was the catty over-opinionated 10-year-old who thought too highly of himself when I first started reading it. So, you know, it was a fitting book. That is so funny.

SPEAKER_03 2:09

I love that. I love that. But who gets to set the social norms? That's my question.

SPEAKER_02 2:17

That's always the right question to ask, Camille, to be frank. It is amusing that we are living with, say, books like Emily Post and books like the Carnegie's How to Make Friends and Influence People that kind of ingrained these social norms from the 20th century and the early 20th century, no less, and bring them forward to today, which I think could be a little problematic in some ways.

SPEAKER_03 2:41

I think that tradition is pressure from dead people.

SPEAKER_02 2:51

But sometimes those traditions have purpose, but other times they are just absolute rubbish.

SPEAKER_03 2:59

Yes. Christina, thoughts?

SPEAKER_05 3:01

I think that I agree. I think there are some traditions that are awesome. And if you are all for the tradition because it's something that you enjoy doing and then you want to pass on your kids and just create a really good atmosphere around that tradition, that's one thing. But if you're just doing tradition because it's tradition, sister, we gotta talk.

SPEAKER_03 3:22

Yeah, yeah, no, I agree with that. And but I feel like that's also a really great segue to our topic today is like, well, no, when you're when you're doing things just because it's become the norm of the times, right?

Two Viruses Shaped By Human Activity

SPEAKER_03 3:34

How does that later affect us? And we're gonna look at that into really nitty gritty details of two case studies of two viruses, Machupo and Zika, and how they're affected by human activity, right? Like politics, like agricultural practices, like colonization, deforestation. And these are things that were at some time socially acceptable in the way that we were doing them. But that doesn't mean they don't have negative effects on us, right? So yeah, so that's what we're jumping into today. Alex, do you want to kick us off and define the first virus we're talking about?

Machupo Basics And How It Spreads

SPEAKER_02 4:05

Absolutely, yeah. So as Camille was saying, we're gonna start with matupa virus. So matupa virus is a new world arenavirus. And so arenaviruses and new world arenaviruses specifically are these RNA viruses that circulate in the Americas and that have a reservoir in rodents. And arenaviruses are relatively unique in their replicative strategy in that they're ambison, so they have differing transcriptional polarity on the two segments. But at any rate, machupo is endemic to Bolivia and has an animal reservoir in the large vesper mouse. And when this mouse is infected with Machupo, it tends to lead to chronic asymptomatic infection with viral shedding in its excreta, so its urine, its feces. And so aerosolization, the creation of a fine dust or mist of this infected rodent excreta tends to lead to rodent human spillover events through inhalation of these infectious viral particles. And most spillover events tend to occur as a result of this, although infection with matupa virus in humans can also stem from direct contact with infected rodents through other means. And incidentally, there have also been some limited reports of secondary transmission. I'll get a little more into this outbreak. We'll talk more about it later, this San Joaquin outbreak in 1962 to 1964. But there were some scientists from the US who came to help the Bolivian government in their response to what was going on and to characterize what this virus even was, because that outbreak was one of the first outbreaks of Bolivian hemorrhagic fever, and it was one where the pathogen had yet to have been characterized. But some of the scientists who came down there to respond to the outbreak got sick, and then they actually ended up inadvertently infecting their wives in Panama when they went to visit them in hospital, which was yikes. I would have been so mad if I had been married to one of these folks, right? Oh yeah, yeah. Yikes. Yikes. You come all this way and you get me sick with a disease that I didn't even sign up for.

SPEAKER_03 6:08

Yeah, yeah. That'd be mad too, yeah. Yeah, I did not know you could have secondary transmission of it. That's really interesting. And just to clarify for listeners, so the Bolivian hemorrhagic fever is caused by machupa virus. So they don't, for some reason, just call it an infection with machupo. They call it Bolivian hemorrhagic fever, likely because that's where we found it. But that is just one little no I just want to throw out there because usually, whatever you have, if you have influenza, they're like you have the flu. So no one says you have matupo, they're like you have Bolivian hemorrhagic fever. So just throwing that out there as a note.

SPEAKER_02 6:42

Exactly. No, that's a great point, Camille. Yeah. And so BHF, the Bolivian hemorrhagic fever, that condition in humans, it has a pretty decently high case fatality rate. It's about 15 to 30%. And so to give you an overview as to what happens when you're infected, so there's initially a three to 16-day incubation period, and that tends to be followed by this sort of predromal phase, so a phase of nonspecific illness that lasts about one to five days. And it's characterized by symptoms like fever, myalgia, muscle pains, headache, nausea, dehydration, and malaise, fatigue. And as a result, it's pretty hard to diagnose because these symptoms are pretty common with a variety of different types of illnesses that are also endemic to the region. It's pretty easy for machupo to be misdiagnosed for dengue, for instance. Um then oh yeah, sorry, go ahead.

The Clinical Puzzle Of Hemorrhagic Fever

SPEAKER_03 7:31

If I can jump in. Yeah. Christina, if someone is presenting with these, is that just the worst thing when it's like you have a fever and you don't feel well? I feel like it could be so many things. What is your kind of first step when you start seeing something like that in a clinic?

SPEAKER_05 7:44

Yeah, I feel like the first steps, let's say you're in the ED and you have a patient that comes in with all these generalized symptoms. The first thing you're probably gonna do is get some cultures on them and get like a respiratory panel, just because those are the most common things that you see, right? But when all that comes back negative, then it really gets down to a little bit more of the nitty-gritty. When you're thinking infectious, you have to think about the geographic region that you're in, and then that kind of gives you a more specific picture of what you could be dealing with. So here in the Galveston area, for the most part, something that's a little bit more common that we see when all that comes back negative, but it looks like there's something infectious going on, is typhus. And so that's something that we think about here. But I could imagine in Bolivia or wherever this might present, that could also be at the top of their differential as well.

SPEAKER_03 8:34

And I think that's wild that people don't think about it, that you can see like myrian typhus in Balveston. But I think it's also hard when you live in a place where there might be like multiple diseases that could be vector-borne, right? So, like, say you get bitten by a tick in upstate New York, where I am now. Yeah, we might assume you get Lyme, but that's not the only thing you could be exposed to, right? And so in some places, if you've been exposed to mosquitoes, we don't know what you might have picked up, right? And that could also mean that something like this is not your immediate thought, right? If it's maybe not suddenly at the top of that differential diagnosis list. So I think that's something to keep in mind.

SPEAKER_05 9:11

I will say of the clinical picture that we always have to ask, and that we do always ask is have you recently traveled anywhere? So that's really important to ask in any situation, especially when you're, let's say, in the ED or you're initially presenting to a clinic and these providers don't really know you that well. That's something that you always have to ask because you're right, Camille. Like the travel history, where a patient's from, where a patient has lived, has a significant impact on what they could have been exposed to in the past or in their recent history.

SPEAKER_03 9:41

I think I also wish something that was asked more often is have you been around animals of any kind, like whether they're domestic, whether they're farm animals, like whatever it is, or wild animals. I think that's something that I wish was like just more of an automatic question. And I get why it's not necessarily, but I just think there's so many potential zoonotic diseases that we can pick up that are really important to catch quickly. And then if we don't ask that, we don't know, right?

SPEAKER_05 10:09

Yeah, that's true. I would say they're probably less likely than the common cold or something else. But true. I agree. Those are definitely some questions that we should think to ask, especially in really agricultural places and rural places. You're right. Like Texas, we have so much cattle here, we have so much wildlife that lives right next to us and among us.

SPEAKER_03 10:29

Yeah, I agree. Yeah, totally. I remember when I would go to like the pediatrician when I was a kid, they would have someone with them and they would be like, oh, Camille lives on a farm, and they would just give me this look like what have you been exposed to? But that's probably more realistic, right? It was a good thing that my pediatrician knew that I grew up on a farm because if I ever got sick, they would be like, oh, like were you out putting up fence? Did you get exposed to tetanus or things like that? And of course, not how my vaccines, but I just think it matters to have that, just the history of a person, right? Because it's never like an accusation. It's like a where have you been? Or like, what do you do, or what are you around? And I think that's really important, especially because if we think of something like Bolivian hemorrhagic fever, there's no licensed medical countermeasures. We don't have any vaccines approved for treating it. And it's just something that we can see this really high case fatality rate and we don't have countermeasures. So, like, we do want to catch it because we want to know and make sure that we can basically give people the supportive care that they need and get that diagnosis right. But now that we're all kind of on the same page on what Machupo is.

Bolivia Land Reform And Mouse Habitat

SPEAKER_03 11:30

What we really want to discuss with this is how changes in land use are what is really driving its spread. So it all really comes down to its annual reservoir, which Alex mentioned is the large vesper mouse. And it also comes down to politics. So, Alex, do you want to get into a bit about the large vesper mouse as the reservoir?

SPEAKER_02 11:49

Absolutely. Yeah. So the large vesper mouse itself has a preference for your grasslands and forest fringe sort of environments. And so these are areas that are adjacent to cohesive forest environments, but that are transitional in nature. And the large vesper mouse also has a preference for these peridomestic environments. And so it has peridomestic behavior. So that means that it has a preference for being near or around human habitation or in human dwellings. Like, and in fact, during that San Joaquin outbreak in 1962 to 1964, CDC researchers saw that that the large vesper mouse kind of behaved akin to the common house mouse, like mus musculus, in the dwellings of these people in Bolivia. And so it's worth noting that land clearance, of course, plays a significant role in expanding the habitat of a large vesper mouse because that can potentially increase its peak population size and population density and put it into a position where it's in closer contact with the people. And when it comes to that, it's worth thinking then about how Bolivian land use policy would have gone about altering the ecosystem in which the large vesper mouse would have started to proliferate. And so first let's look- Can I jump in real quick? Yes, yeah, absolutely.

SPEAKER_03 13:04

Okay. I just want to throw out there because I feel like this always comes up when we talk about your what people are exposed to or whatever. And I think there's sometimes judgment in it. And I just want to throw out there that literally anyone can get a mouse in their house. And why do I say this right now? Because I woke up at 2:30 this morning to a noise of something moving across the floor. And it was a field mouse that had somehow gotten in. And I immediately, of course, you know, me, I'm like, disease. I'm like, oh my God. And why was it in my house though? Because I'm surrounded by agricultural land and what is being done. They're prepping for spring planting. So I'm sure this poor little mouse lost its home as they're tilling fields and they're like doing stuff for all kinds of agricultural purposes. And it was also really cold. We had snow yesterday, which is nuts. It's April right now as we're recording this. Wow. I'm sure it just was like, look at this warm house. So as soon as I saw it, because I had edited the script, I was like, it's a peridomestic pest. It's in my house.

SPEAKER_04 14:03

Oh my gosh.

SPEAKER_03 14:04

So I just want to throw that out there. It doesn't say anything about like how clean your house is or like how tidy you keep it or like how nice it is. It doesn't matter. Like we're just in the environment. And sometimes they come in. So I just want to throw that out there as an anecdote of if I'm punchy, it's because I'm really tired because of this experience to like capture it and take it outside. So, anyways, I just want to throw that out there because if I lived in Bolivia, I might have had one of these in my house instead of just a regular field mouse. So just throwing it out there that anyone can get a mouse in their house.

SPEAKER_02 14:40

That sounds like a children's book. No, that's a great point, Camille. And uh yeah, no judgment there by any means. When you live on Earth, you have to deal with the fact that you have other life forms around. We're not the only things, and sometimes we forget that.

SPEAKER_03 14:56

Yes. So, anyways, I just thought that was a great anecdote. But continue, tell us more about Bolivia and policy changes that really drove this, also.

SPEAKER_02 15:04

So, yeah, so pre-1953, Bolivian landholdings were largely held by these large-scale landowners in a hacienda-like system. So this was akin to the old Spanish colonial practices that were then maintained following the end of the Spanish colonization period. At its peak, up to about 90% of the arable land in Bolivia was controlled by some of these large landholders like that. Yeah. And so you can imagine that these landholders had a significant amount of political power that came along with that landownership, right? And so that led to the disenfranchisement of your farmers, indigenous peoples, and the middle class alike. And all of these groups uh ultimately ended up uniting behind the Movimiento Nacional Revolucionaria or the MR, which was this Bolivian political party in the 1952 Bolivian National Revolution, in order to try to overthrow this oligarchical political system that entrenched the power of these landholding elites. And so when the MR gets to power, of course, this is a pretty disparate coalition that they've stitched together and they're under pressure to deliver for these people, right? They you promised land reform, now people they want land. So how do you go about giving the land? So in 1953, the following year, the MR passed this law known as the Agrarian Reform Decree, which sought to redress these long-held land grievances through redistribution. And so it broke up the lands of these large landholders in the more populous western highlands and western Yungas regions of the country. So the but in the eastern lowlands, where Machupa virus was endemic, like in the department of Beni, which is this northeastern province of Bolivia, the decree opened the door more to these land colonization schemes because this was a very sparsely populated area, very broad, overall, only about 100,000 people over a massive land area. And so these land colonization schemes were essentially these programs where individuals were encouraged to settle and establish productive farms, be it the poor or the supporters of the MR that were directly encouraged to go out to these spots. For instance, the agrarian reform degree prioritized individuals whose families had suffered losses during the Bolivian National Revolution as well, in terms of having priority for getting land out in these places. And so that that sounds all nice and dandy, right? This empty land that's sitting out there, we're putting people to work, giving them the land. The land wasn't really empty, though, because there were these indigenous peoples who had been on the land for many years before any of these colonists ever came out. And uh and these communities were already marginalized. They were already outside of power, being so far away from the seat of political power in Bolivia and had long been neglected by the central government. And this just followed in that pattern of neglect for these people. And so these communities often had these collective titles to these lands that were then pushed off by colonists whose claims were then recognized and supported by this government that was enacting this land reform decree in order to go and satisfy its power base. And so the occupation of these traditionally indigenous-held lands then drove land clearance by the indigenous people for subsistence agriculture. They wanted to go about maintaining their way of life and just live productive lives, and so you need food to do that, and so you need to clear some land. And so, as a result, that ended up expanding the habitat of the large vesper mouse because then people's living spaces grew closer to the large vesper mouse, and that meant that spillover events between infected rodents and the indigenous peoples and the people who were living in the Department of Benny just became more likely. And it's worth noting that the shift in land use not only increased the range of the large vesper mouse via land clearing, but the agricultural practices that happened on those lands also encouraged an increase in the population size of the large vesper mouse itself. Because the use of DDT, for instance, which was a lot more common in the 50s and 60s than it is today, it poisoned a lot of the local cat population. And so that meant that the animals that were feeding on the large vesper mice, these cats, were around in much more decreased numbers. And so the large vesper mice were able to establish a habitat niche inside of the dwellings of some of these people, as well as in these farmlands at higher rates and at higher densities than would have been imagined otherwise because of the absence of predation. And so this was the perfect storm in many ways for a Bolivian hemorrhagic fever outbreak. And so the outbreak that did result in the town of San Joaquin and in some of the surrounding areas within the Department of Beni was the largest Bolivian hemorrhagic fever outbreak that has ever occurred still. And so there were about 637 cases, with about 25 to 35% of those resulting in death. And it's worth noting that colonization always has unforeseen consequences, right? And that agricultural practices, while vital to feeding our population, can also place it at risk in terms of these rapid changes in the ecosystem from altered land use. And I think that there's an old say of everything in moderation, right? And I think that holds when it comes to land use as well. Anything that happens really fast in an ecosystem. Yeah.

SPEAKER_03 20:19

Yeah, absolutely. How long did it take after this outbreak for recognition to come that it was the land use practices and the displacement of indigenous populations that led to deforestation that really allowed this to come, that it was human activity that perpetuated the outbreak? Do you think that's a pretty recent realization?

SPEAKER_02 20:40

Yes, it does seem to be relatively more recent because when it came to this sort of idea that a land use policy, marginalization of the indigenous peoples, that this altogether might be driving some of these cases, that idea only emerged in the historical literature, so in the field of historiography, in 2005. And these cases were in 1962, right? So a pretty long time. So in terms of how they were able to control some of these later cases since then, it was found that rodent control played a significant role in this. So reintroducing cats in the population, trying to cease the use of DDT, and taking efforts to go about trapping these mice in order to make sure that they were no longer in close proximity to people. And that did help a long way in terms of reducing these cases, but it never really addressed the root causes of what was driving it. And in fact, a recent analysis that I've been doing as part of my own research showed that cases of Machupa virus more recently, so say 2007, 2008, there's a correlation that you can see between those cases and then deforestation within the preceding three years per NASA satellite data. And those land colonization schemes, while no longer government sponsored, they're still going on unofficially. And so these same dynamics are still at play, and we still see these. Cases going on. And so I think it's a really cool story, personally. I started doing this for my research and I was just like, this is really neat. So I thought that it would be fun to share.

SPEAKER_03 22:09

Yeah.

Fast Change And Who Gets Hurt

SPEAKER_03 22:10

Yeah. And I think it's a really important story. I want to touch on a couple of things you said because I think they bear emphasizing that human activity often changes ecosystems really quickly. And as you said, anything that happens fast in an ecosystem, it's rarely a good thing, right? Ecosystems change on a geologic, slow time scale. And when we speed that up, we truly don't know and can't foresee the consequences. And it's often only in hindsight after a population has already experienced suffering that we look back and see this. And it's honestly scary to me how often we all have to touch the burning stove. We know something is not good and we learn from that, but it's like we forget because we're like, oh, certainly maybe I know that deforestation or this particular agricultural practice is not good. But then there's always the economic aspect, there's the political aspect, there's the social aspect of like, where do people go? What do they do for work and purpose and these kinds of things? And I think too, we oftentimes make changes. I think humans tend to move fast and break things, and we don't always think through the consequences, even for other people that aren't just in what we consider like our community, but that are in the broader community of humanity, and we don't consider how much things affect them. And I think that's something that we particularly see become very emphasized when we're looking at disease and how disease spreads. It often is hitting people who are already disenfranchised for some reason, whether that's politically, economically, socially, whatever it is. It's something that shows us where our own fault lines are. And I think in some ways that's also very powerful as a story to look back at and learn from, right? And not even just that we can predict it going forward, but that we can realize the damage we've done and try to do better. Christina, thoughts?

SPEAKER_05 23:56

Yeah, no, I completely agree. And part of me also questions, I know you phrase it as how many times do we have to touch the burning stove to learn? It's also me questioning and wondering, like, how is it about learning these patterns and learning from what we've done in the past, or have we learned?

unknown 24:15

And is it just something that is almost like a thing for human nature? You know what I mean?

SPEAKER_05 24:21

I think Alex said at the beginning of this podcast, almost to do things that we know are going to harm ourselves and those around us and the environment around us, but we still end up doing it because it's beneficial for us in the moment. So that's something that I think about all the time, and I think about that a lot when it comes to the actions that humanity chooses to take on a lot of things. And so yeah, I think this is a really important case study to talk about, Alex. And I'm glad that you brought it up because I think that we can learn as a community, as a people, and I think it's important that the grassroots speak up and the people who are truly I have my dog in the bag. And I think it's important that the grassroots speak up and that the people who are truly affected by the decisions that are made in our society on an everyday basis have a voice. And if they don't have a voice, then us who do have a voice speak up for them. So I'm really glad that you brought this case study up on. Thank you, Christine.

SPEAKER_03 25:16

I agree, I agree. Yeah, I'm really glad we're covering this. That's super important. I think in so many ways, you're right. Do we sometimes see things and then we still don't act? Because it is people make the decisions in the moment that benefit them, even if it's the long-term, long story, we don't always see all the way to the horizon, right? We're just looking at the ground in front of us. And people get hurt by that. And I think in many ways, some people profit off that hurt. And I don't know, it's the goal of mine personally as a human to not profit off of other people's hurt. I think that really matters. Likewise. And there's so many ways that little things that you can do to try to live without doing harm, right? Like whether it's being mindful of language, whether it's what you're investing your time and effort and money and whatever, I think that really matters. So I'm glad you brought that up, Christina. I think that's a wonderful point.

SPEAKER_05 26:07

We're doing something good with this podcast. So let's keep it at mind.

SPEAKER_02 26:11

I must say I really love that example that you used, Camille, about touching the stove. I want to just echo what Christina was saying there. That was such a brilliant analogy in terms of describing the way that we do have a tendency of going back and repeating the same sorts of mistakes again and again and pursuing these activities that do seem to be beneficial to us in the short run, but that in the long term have a lot of consequences that may be disastrous for other people who are bearing those costs, or for all of us writ large, or just things that we haven't even mapped out, right? We just go down these courses of action that we don't even know what it's gonna entail, right? Um and to echo also Christina's point, I completely agree that those of us who when we have a voice, when we have the privilege of having a voice and having a platform to be able to talk about these things, we have an obligation to go and to talk about it. Because when it comes to some of those indigenous peoples in Bolivia, yeah, they've been on the sidelines of every sort of government that's been in power in Bolivia since the Spanish came over and colonized it in the 1500s. That's a pretty tough track record to go up against. And it means that a lot of folks may not be listening to what's going on for them.

SPEAKER_03 27:25

Yeah. I'm always hopeful that emphasizing the shared humanity allows things to move beyond the realm of just data and numbers into something that is truly real, to being displaced. And then not only was there loss in being displaced, but like in how that land was used and held previously in stories and practices that I'm sure revolved around that land being the way it was, right? Yeah. And these are things that we can't quantify, right? That's not something you'll ever find in stats or something like that. But that doesn't mean it's not a very real impact on the world. Just that there's the stressors of living with that, but also the history that you lose, right? And that's human history. And that is something that we can't get back, but it's something we can try not to destroy going forward. And I think to just honor that there's different ways of existing in a space and that no one has the correct way or the way, there's just people with the power to determine a way. And that can change and that can shift quickly, right? You see this even with M and R. It was certainly not perfect, right? People certainly suffered in it. But the fact that people were able to shift from something like a hacienda system into something else shows that we're dynamic and that people are dynamic and people can change and learn, not continue to perpetuate cycles that we inherited, but don't want to continue to perpetuate in the world. That's something I've been thinking about a lot lately.

SPEAKER_05 28:52

Amen.

SPEAKER_03 28:53

Yeah.

SPEAKER_05 28:53

Let's not touch the brainstone again.

SPEAKER_03 28:56

Yes. But we do have a here. Um yeah, so here we are just solving the world's problems. Um but I do want to, you know, one podcast at a time, one podcast at a time, one case study at

Zika Goes Global Through Travel

SPEAKER_03 29:12

a time. And I do want to get into our next case study because I think it also is really valuable to talk about. And so this is one that people are definitely likely more aware of. Um, Zika, it definitely lives more in our public consciousness as a threat. And I'm gonna say, I think it's important to say it in the beginning. I think it lives in the public consciousness as a threat because it impacted Americans. And to a lot of people, it's not real until it's in your backyard. And that's not right, but I do think that is worth acknowledging that to many people, that's why they know it at all, right? Because it isn't originally from the Americas. Machupo is a new world arenaver, but Zika is originally was isolated in Uganda, but it moved here because of human activity. And we all bought into this system of human interconnectedness, right? So it's not necessarily anyone's fault when diseases move, because we've all sort of bought into these things. And so I just want to put out there that it's something to think about that a lot of times we get empathy fatigue or we're only looking at something, but it becomes very real when it's something that we're like, oh, I have family in Florida and they could be exposed, right? But that doesn't mean it's not a real threat to all humanity and it shouldn't just be of interest to us when it crosses into like what we view as our backyard or our home turf or like our, you know, group of people that we care about. I firmly believe this. I feel like I've said it on multiple episodes. We're only as healthy as the least healthy place. And if everyone's health on the entire planet was not interconnected, something like COVID never could have happened, right? And so I just think that's worth throwing out there before we get into this case study. But again, similar to something like Machupo, like I want to kind of let us get into an overview of it, but then also how land use has played a role in the Zika virus outbreak. So, Alex, take us away with kind of the overview of Zika just to get everyone on the same page.

SPEAKER_02 31:00

Absolutely. Yeah. So Zika virus is a flabby virus. So that's a type of single-stranded RNA virus that tends to be transmitted by vectors, so like ticks and mosquitoes. And as Camille was saying, yeah, it was initially isolated in Uganda in 1947, and it was largely found in Africa and in Southeast Asia until there was a 2007 outbreak in Micronesia. And then Zika subsequently spread across Oceania over some of those ensuing years and eventually came to the Americas, leading to that 2014 to 2017 epidemic in the Americas. And I don't know about y'all, but I certainly remember seeing some pretty alarmist reports on CNN or 2015-2016 about a Zika virus, this new threat. Um it wasn't exactly all that new. It was just new to us. It wasn't new.

SPEAKER_03 31:49

It was new to us. Yep, it was in our backyard. It was newly in our backyard. Yeah.

SPEAKER_02 31:54

Exactly. And so, yeah, in many ways, you can probably attribute a lot of its spread due to increased human travel and international maritime trade and things like that. And so human activity played a key role in terms of how it is that these mosquitoes ended up traveling, but then they also played a key role in terms of how Zika ended up eventually spreading once it came into the Americas, right? But we'll get a little more into that later, of course. So, due to human activity, though, yeah, Zika can now be found pretty much on all continents except Europe and Australia, and of course Antarctica. So Zika is spread by the bites of infected ietis mosquitoes. It's predominantly by the species known as ietus agypti, which is a key vector for other sorts of flavby viruses. Ietis allopictus also plays a key role as well. And to just give you a general idea as far as some of the symptoms of disease and how disease progresses, there tends to be about a 3 to 14-day incubation period post-infection. And then there's an acute phase of about two to seven days, and that tends to be associated with rash, fever, myalgia, arthralgia, malaise, and conjunctivitis. And so it's worth noting that most cases are pretty mild. But this is not like Machupa, where a lot of these cases progress ultimately to death or to some awful hemorrhagic neurological set of symptoms. But then the key sorts of issues with Zika stem from some of the complications that arise, especially in pregnant individuals. Because something that was especially of concern during that initial outbreak in the Americas was of this microencephaly and of other congenital malformations like limb contractors, eye abnormalities, hearing loss that were observed in about 5 to 15% of all infants that were born to pregnant women that were infected with Zika during pregnancy. And so, of course, that made it a big concern. And it's worth noting that less commonly that so myelitis and neuropathy can also occur in some older individuals that are infected with Zika, but predominantly the big public health impact is on that pregnancy side of things and the issues that can result in unate. And how does that happen, right? It's typically because a pregnant person, when they contract Zika, the virus can pass through the placenta and then it'll interfere with fetal development at that point. And it's worth noting, of course, similar to Machupo, that there aren't any vaccines that protect against Zika. And the mosquitoes that spread it, they tend to bite during the day, right? You always hear people warning you about going out at sunset or at night with mosquitoes, but they can bite a lot during the day as well. And the Aedas mosquitoes, that's they like to be out when we are out too.

SPEAKER_03 34:27

No, I think that's a really good overview.

Containers Of Water That Breed Mosquitoes

SPEAKER_03 34:30

I also have another anecdote here as we get into land use regarding Zika. This is, of course, spread by mosquitoes, as you said, and they're very adapted to using human containers that could be plants, that could be like plant pots, as like breeding grounds, could be old tires, and that really increases the mosquito burden in an area and also the risk of a the chances of an infected mosquito biting a human. I grew up on a farm and we had rain barrels. This is like the public health nightmare, probably. But I was in upstate New York, so there's not really anything we're too worried about for mosquitoes. You could get triple E, which is Eastern equine cephalitis, but it's pretty rare. But I can remember as a kid, I would sit and watch these rain barrels for like hours because I would see things swimming in them. And it was the mosquitoes would lay their eggs. And then, of course, like the hatchlings because he was making like a really grossed out face at me. But I thought it was so cool because you could watch them move around. And because I mean, it was filled with them because there were just these rain buckets that we kept, and then we would dip the watering can in and water the garden or whatever. So it could be literally anything, right? And that's a human container, but that doesn't mean to say there's not puddles or like swamps or whatever or stagnant ponds or things like that.

SPEAKER_05 35:42

Stagnant ponds, water and tires. Yeah.

SPEAKER_03 35:46

Yep. Yep. So, anyways, I just want to throw out that anecdote. But yeah, and then I was always so disappointed when my dad would dump them out because I was like, oh my god, I like entertainment. I was watching those little the little dudes hanging around in the water. Yeah. So, anyways, but my parents knew. They were like, no, we're not gonna perpetuate this. They can hatch, but they can't become the full-fledged thing. So yeah, but anyways, Alex, tell us more. Just another anecdote from the farm.

SPEAKER_02 36:15

Oh my god. I mean, I always enjoy hearing these farm anecdotes.

SPEAKER_03 36:20

Listen, Alex, I didn't have TV. I didn't have a TV.

unknown 36:25

Okay.

SPEAKER_03 36:26

So on YouTube realized that was interesting to me because it was a moving, it wasn't a picture, it wasn't on the screen. I was not allowed a TV when I was a kid growing up. I feel like that sounds so culty, but I couldn't imagine. There's no TV. So I was like, mosquitoes hatching, fascinating.

SPEAKER_02 36:44

I don't feel like I'm in a position to judge. I read Emily Post. You were watching mosquitoes in rain barrels. So I feel like it's a meaning.

SPEAKER_03 36:55

Oh my gosh. All right. Christina, you've got to even this out. What weird childhood thing did you do? You gotta even this out. It can't just be Alex and I.

SPEAKER_05 37:05

Oh, geez. What did I do? I'm gonna have to think about this one because I was quite the crazy kid. I'll let you think about this one. Give me some more.

SPEAKER_03 37:14

Okay. All right. Think about it. Think about it. Okay. We'll revisit We'll circle back because we can't be all the lunatics on this podcast.

SPEAKER_02 37:26

That's a great story, Camille. And it really does point to, yeah, exactly the same sorts of issues when it comes to the mosquitoes that spread Zika as well. But the mosquitoes in upstate New York got pretty adapted to that rain barrel, but the ones that spread Zika have become really used to things that are a lot more common in urban environments, like tires and plant pots and things like that as potential breeding grounds. And that has enabled an increase in the mosquito burden in an area and the chances of an infected mosquito biting a human. And it's worth noting that ultimately there were some recent studies that found that some of the key drivers of Zika in the Americas have been changes in land use, similar to Machupo, right? In terms of going and creating these sorts of new habitat niches for mosquitoes, in this case, to adapt to human behavior and to grow. And because stagnant pools of water and stagnant ponds aren't just a rural phenomenon. If those stagnant pools can be found in other human-made structures, then that's all the more reason that this can be an issue that comes up later down the road.

Climate Shifts And New Disease Frontiers

SPEAKER_02 38:26

And of course, climate change, climate variation plays a role in these sorts of phenomena as well. I know you were talking, Camille, about how the Eastern equine encephalitis virus is really the only potential mosquito-borne virus that one could really be too concerned of in upstate New York. But something that crossed my mind when you were discussing that was about how the range of, say, dengue, the range of West Nile virus and the mosquitoes that carry those keeps on creeping further and further north.

SPEAKER_05 38:53

Yeah, that's real though. It's the reality that we're heading to. Exactly. I just say it right now. I had dengue, and we don't want dengue. That's a nasty little virus right there. Wait, you had dengue? You know someone with that had dengue?

SPEAKER_03 39:09

No, I had dengue.

SPEAKER_05 39:10

When I was younger.

SPEAKER_03 39:11

Wait, what? You've never shared this. That's why. I had dengue. Yeah. That's why. Okay. I'm like really curious.

SPEAKER_05 39:19

So I spent a lot of my teenage years living in Latin America, and I got dengue while I was over there. And it was like a fever dream. It was seven days. And I think I remember maybe 24 hours in those seven days. It was horrible.

SPEAKER_03 39:34

Whoa. Yeah, I mean they call it bone break fever, right? That's not its colloquial name for nothing. That's supposed to be truly agonizing. That is unreal. I never knew that.

SPEAKER_05 39:44

Yeah. And it's actually a lot more common than you would think it is, you know, in the rainforest in Latin America, and I'm sure in places with similar climates. But yeah, same thing with Zika, like where I used to live, it was a fairly common thing to get. Yep. Because I lived in the rainforest and it really was a little town in the middle of the rainforest. And when you talk about encroaching into nature and building these human civilizations or these human places within nature and disrupting the environment and the ecosystem, that was like the definition of where I lived. And so you were surrounded by the rainforest with just these little plots of houses structured within. And any little divot in the land or any tire you left out was filled with water, and the water just stayed there and it was just breeding onto the mosquitoes.

SPEAKER_03 40:33

I mean, see, but that's so interesting because so, like where I grew up, I was in the mountains, but there's definitely swampier areas too, right? And when my dad was out clearing land, right? So agricultural practice, similar to what you're talking about, like that's where it's happening. And he got triple E. He got Eastern equine encephalitis from a mosquito bite and got incredibly sick, right? And you know what the worst thing is though, he never told me about this until after I had gotten my doctorate. And I was like, dude, I study infectious diseases. Like, why was this never a dinner conversation topic? I need to know this. What epigenetic changes have you passed on to me because you are so sick? I need to know these things.

SPEAKER_04 41:10

That is so funny, but that is also really interesting. And I don't want to say, oh my gosh, that's cool because I feel bad for your dad, but it's very interesting.

SPEAKER_03 41:20

I mean he lives, he's fine. There you go. But it is cool in a way. I thought it was cool. Yeah, it is. I'm sure he didn't think it was cool, but you know, like that's pretty neat because it is very rare. Yeah, it's cool. It's cool. It's a cool story to tell. Was it cool when it happened? Yeah. Cool story to tell though. I think it's really cool you had Dengue.

SPEAKER_02 41:40

Absolutely.

SPEAKER_03 41:41

I think it's cool you had it. I'm sure it was suffering. And I'm sorry that kid you suffered, or like you at any stage of life suffered. But um, I do think it's a cool story. I feel like if I had ever did it, I would brag about it. But maybe that's just showing my infectious disease bent towards life. I was talking to this guy the other day, and he was telling me how his mom had malaria eight times. And I was like, dude, that is the coolest thing I've ever heard in my life. What are you talking about? This woman said malaria eight times. I was like, that is absolutely fascinating. I know, I know. She just gets it a lot. I was like, okay, wow. That's tough. But also like unreal. Again, a thing I would brag about and be like, yeah. If that happened to me as a kid, that's what I would brag about all the time. I would never shut up about it, Christina. I would totally never shut up about it.

SPEAKER_02 42:40

Some people have brushes with celebrity. You have brushes with infectious disease.

SPEAKER_03 42:44

Let's talk about two talks.

SPEAKER_02 42:46

But yeah, you raised, I think, also a really great point that I wanted to touch on about Zika and land use fragmentation when you were talking about that sort of small town environment that you were in when you were infected with Dengue Christina as well, because that was something that sort of fragmentation in land use can then increase the frequency of human mosquito contact, right? Because it creates these new natural opportunities that already existed and combines these with these little man-made opportunities for infection. And so these transitional areas, those small towns, these rural areas and things like that, where we can see agricultural activity like you were alluding to earlier, Camille, these help to alter these sorts of dynamics then of the pathogen vector host relationships, and then enable the further opportunities for these pathogens to then go and expand their range and exploit new niches in the environment. And so that's something that we see with Zika, certainly, but we definitely see with Dengue as well. And I hate to say it, but you were a great case study of that, Christina. You're welcome. But yeah, so yeah, it's just really interesting to think about how all of these things really do. Come together and those sorts of shifts, but it's worth noting. We don't really see them just with Zika, just with Machupa. This is with a lot of different diseases that have animal reservoirs or animal vectors that are on hand. There were similar studies that have been done about Ebola as well that have shown that deforestation is directly linked to then the likelihood of further infection and that forest loss and fragmentation are strongly associated then with the locations of Ebola cases. And that's something that we can see with other diseases as well, like with hendrovirus, which is a bat-borne disease. We see in Australia that changes in the habitat of these bats as a result of human activity, it's led to shifts then in bat behavior. And so the bats then end up spending more time in farmlands and in areas where humans and where other livestock as well are more present, and that can lead to infections there as well. And so it really, you know, I think ties together with the whole mission of this podcast, right? It's all about one health, right? It's all about these interconnections between the pathogen of the host and some of the vectors potentially or reservoirs that are in there as well. And just I feel like oftentimes when we're thinking about going and clearing some land, for instance, to go and build something new or to go and establish some farmland somewhere, you might not necessarily think about how some of these habitat changes can affect the ecosystem, not just in that habitat loss, but also in terms of what habitats are gained, what habitats are created by this human ecosystem.

SPEAKER_06 45:31

Oh, okay.

SPEAKER_02 45:32

And what are some of the winners out of this human ecosystem change? And I feel like Zika and Machupo really are great examples of that.

SPEAKER_03 45:39

I absolutely agree. Yeah. Good point out. I completely agree with that. And thanks, Alex, for suggesting this episode and diving into scripting and stuff like that. And I also just want to emphasize I didn't just tell you those anecdotes just to like give you my lore. I want to emphasize that these things can happen to anyone, right? Yeah. And I think that matters, right? This human aspect. So anyone could find an exposure to like a peridomestic animal like a mouse or to something like mosquitoes, or like has had a rain barrel that they didn't empty out or something like that, or has been traveling or living in a place that was on the edge of rural, or even in an urban area where we create all these new environments. And I think that that's something important to kind of bring back to always that I think Alex said it really well that this is a One Health podcast and this is about humans and animal and environmental health. And it's also about almost the shared story of humanity, which is very often entwined with this thread of disease. And a lot of times our own actions are what's leading to like a further entanglement with disease. And we don't even see it until after the fact, until after we can look back and see where things started. And I think that it's important to not only see where things started, but also start to do things that are predictive, right? Like Alex, you mentioned the work that you're doing. I think that's really fascinating to be able to look and say, we can correlate that there's something like deforestation and then you can see a rise or an uptick in cases. Those things matter and they're so powerful. And I think we have the tools to build a better world. We just have to imagine it. And I don't think you can imagine a better world and build towards it until you get this feel for like where we came from, you know? And I feel like this podcast is the reason I'm always just I'm always excited to be on the podcast couch with you all, no matter if we're all over the world or whatever. I think that's something that really brings me back to it. So I'm grateful to everyone for listening and for also for my co-host, Christina and Alex tonight for putting this together because it was wonderful.

SPEAKER_05 47:33

Oh this was so great. Thank you so much for suggesting the topic, Alex. That was wonderful. And I couldn't have said it better myself, Camille. Although I will say, if you're ever just wanting to share your lore girl, I'm always here to hear it. Okay, you don't need an excuse.

SPEAKER_02 47:53

Neither do you this is a safe space for lore sharing. Yes. Thank you both, though, so much as well. I feel like it was really interesting to go and to see more about some of your own lived experiences, how they tie into this narrative that we see with these other pathogens as well. So, you know, it wasn't just lore, it was telling the story. It was putting together another contribution in that shared tapestry and that narrative of humanity. So thank you for that, genuinely, to the both of you.

SPEAKER_05 48:27

Yes, so much. I love our monthly meetings.

SPEAKER_03 48:29

Yeah. Yeah.

Closing Thoughts And Listener Callouts

SPEAKER_03 48:31

And thank you so much, everyone who's listening. We appreciate you joining us in kind of that human story and being a part of the thread of infectious science. So, as always, let us know what you think. Share your lore with us or anything cool. Yeah. And let us know if there's a topic you want to cover. Let us know if there's a topic because we're always open to that.

SPEAKER_01 48:49

So thanks so much for listening. Thanks for listening to the Infectious Science Podcast. Be sure to hit subscribe and visit infectious science.org to join the conversation, access the show notes, and to sign up for our newsletter and receive our free materials.

SPEAKER_00 49:03

If you enjoyed this new episode of Infectious Science, please leave us a review on Apple Podcasts at Spotify and go ahead and share this episode with some of your friends.

SPEAKER_01 49:11

Also, don't hesitate to ask questions and tell us what topics you'd like us to cover for future episodes. To get in touch, drop a line in the comments section or send us a message on social media.

SPEAKER_00 49:21

So we'll see you next time for a new episode. And in the meantime, stay happy, stay healthy, stay interested.

SPEAKER_03 49:27

This podcast is sponsored in part by the Institute for Collaboration and Health, an action-oriented nonprofit that partners with innovators in science and health, working with communities to develop nimble approaches to the world's most challenging health problems.