Hantavirus: How Scary Is It??

Introduction

0:00Hi, I'm Wendy Zuckerman, and this is Science Versus.

0:04The show that pits facts against another friggin' pandemic?

0:15Today on the show, Hunter virus. There's been a lot of reports of an outbreak of a weird virus on the MV Hondias cruise ship. What began as a cruise of a lifetime has instead turned into a major medical mystery and an international crisis. Three people have died amid outbreak of Hantavirus on a cruise ship sailing the Atlantic. The first cases seem to have started with a husband and wife that boarded after a birdwatching expedition.

0:45The couple ended up dying, along with one other passenger. And over the next few weeks, more cases have started rolling out. The French national has tested positive for Hantavirus following her evacuation from the cruise liner MV Hondias. Now, her condition is said to be deteriorating. 18 American passengers from the Hantavirus-affected cruise ship are now being monitored at two facilities in the United States. One patient has tested positive and is now in a biocontainment unit in Omaha, Nebraska.

1:17Global health officials warning there are now 11 total cases of the deadly Hantavirus. Adding that number could go up as the virus can incubate for 42 days. And one thing that's really worrying here is just how deadly this virus is. Something like 40% of people who get diagnosed with it will die. And scarier still, according to news reports, it feels like this Hantavirus outbreak is weird because it's spreading from person to person.

1:48Experts are confirming there have been cases of a rare strain on the ship that can be transmitted between humans. Meanwhile, officials have been scrambling to track down some people who left the cruise ship before they knew Hantavirus was on board. No surprises, the internet is freaking out. Hantavirus will spread. It absolutely will get worse. Why did they let the people off the boat? Why'd you let them off the boat? Why did you let them off the boat? Everybody better wake the f*** up with this Hantavirus bullshit.

2:19We're not doing it again. The Hantavirus, Anamontanavirus. This is crazy. History is about to repeat itself. I have seen this film before, COVID-19. I want to watch a new film, The Titanic. And I'm getting very, very anxious, very nervous. And they should have thanked that motherf***ing shit, but they had the chance.

Understanding Hantavirus

2:37So today on the show, what is going on with Hantavirus? What happens if you get infected? How is it spreading? And how worried do we need to be here? Could this be the next pandemic? When it comes to Hantavirus, there's a lot of people saying... We're not doing it again. And then there's science. Science vs. Hantavirus is coming up just after the break.

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Hantavirus Infection

4:48Welcome back. Today we're talking all about Hunter virus. And this is the first time a lot of us have even heard of this virus. So we're going to break down exactly what it is, starting with what happens if you get infected. Because on the cruise ship, the three passengers died within just a few days of their symptoms starting, which is very scary. So we wanted to know how things can escalate so quickly. And for this, we called up Professor Michelle Harkins.

5:18I am a pulmonary and critical care physician at the University of New Mexico. And she's treated dozens of Hunter virus patients in the ICU. And she told us that there are a couple of dozen different types of Hunter viruses that can infect humans. The one that Michelle generally sees in New Mexico is called the Sinombre virus. And it is a lot like the version that popped up on the cruise ship. Yeah, they're in the same family. We can call them relatives. So if you get infected with Hunter virus and you have all these viral particles in your body,

5:54they tend to attack and go after this specific type of cell. So this virus likes a particular cell, the endothelial cell, and it lines all the blood vessels. It lines a lot of the cells in the lung. What happens from here is that your body starts to mount an immune response to get rid of this invader. And that's often when you can start to get sick in a way that Michelle says might feel pretty familiar at first. So you feel like you have the flu. You're sick.

6:25You have fever, chills, body aches, headache. And it's possible that more of us have been infected with Hunter virus than we think. Studies have measured the blood of thousands of people for Hunter virus antibodies. Evidence that Hunter virus had weaseled its way into their body and then their immune system responded. And they found that in the Americas, just over 2% of people that they looked at had Hunter virus antibodies. A lot of those folks were probably never diagnosed with Hunter virus and might have had pretty mild symptoms.

7:01But for others who get infected, like some of the passengers on the cruise ship, it can get very nasty. In the first week of symptoms, you can start getting GI problems. So think stomach pain, nausea, vomiting, diarrhea. And in fact, more than half of the people who actually get diagnosed with Hunter virus end up with severe symptoms. And that can happen because your immune system kind of gets completely carried away.

7:33It creates this massive inflammatory response. And cause like a war, if you will. It's a whole dysregulation of our immune system that is caused by this virus. This is called a cytokine storm. Cytokines are these small proteins that get secreted by your immune system. And they can go completely haywire during a Hunter virus infection, where they can even start to attack your organs. The same thing can happen with a particularly nasty COVID infection, too. But the thing that sets Hunter virus apart is what happens next.

8:07So as the Hunter virus keeps attacking those cells that it loves, the endothelial cells, and particularly the cells that line our blood vessels, that lining can start to break down. The blood vessels become very leaky. This means the fluid in your blood vessels, the plasma, can now leach into places it's not meant to go, like your lungs. And fluid can start to build up there. If this happens, your lungs can't bring in enough oxygen, and patients will tell Michelle,

8:39Hmm, I'm coughing, or I'm short of breath, I can't catch my breath. And at this point, things can start to go downhill really fast. As your lungs just keep flooding with fluid. That can all progress over a matter of, you know, three, four, six hours and get worse. If you enter this phase and you really don't seek medical attention, you have over a 50% chance of mortality, and you can die within 24 hours. Another thing that can happen here is called cardiogenic shock,

9:13and it's where your heart stops pumping enough blood to get oxygen to your organs. And even if you seek medical attention, your chance of surviving isn't great. We don't have medicine specifically for Hunter virus. Michelle told us that the only thing she can do is really, if you catch it early enough, you can put people on oxygen, or even something called an ECMO machine. This is like an artificial lung, where doctors take your blood out, put oxygen in it, and then pump it all back into your body.

9:46Michelle told us that she'll hook people up to the ECMO, basically to buy them some time, while the virus runs its course. Michelle told us what it was like for some of her patients. She talked to producer Michelle Dang about it. Some of the first patients that I saw came in talking, they were on just a little oxygen, and then rapidly deteriorated, and were put on ECMO within four hours. And it was striking that it can progress that fast.

10:16Can you see that when you look at a patient who's already come in, or expect how they might handle the disease? No. It is really difficult. Some people come in and you're like, oh my gosh, they're going to get worse. And they get better, and they're off of oxygen in a day or two. And then someone comes in that is, you know, you think a young, healthy-ish person that comes in, and they're on two liters of oxygen, and then they're on the bypass machine the next day. So it's, you can't just tell by looking.

10:47So that's part of what makes Hantavirus so scary. It can sneak up on you, and you can get sick really fast, and even die. And there's no vaccine to prevent it. So, you, me, we don't want to get a nasty case of Hantavirus.

Transmission Methods

11:05How do people get infected in the first place? Now, Hantavirus is actually found all over the world. We've seen it on every continent except Antarctica. It's often carried by rodents, but it's also found in animals like bats, moles, and shrews. And usually, just zooming out from the cruise ship outbreak here, people get infected because they come into contact with poo or wee from an infected rodent. We talked about how this can happen with Neil Vora.

11:36He's a doctor who studies spillover diseases from animals to people. So, you know, in other scenarios in which we've seen people get infected with Hantaviruses is that they're living in areas where rodents are also living, right? Now, maybe someone is then grooming in their house, and they're sweeping all these rodent feces. And as you are sweeping and cleaning the house, any dried-up rat crap can kind of turn to dust, go up into the air, and then you breathe that in. And you're aerosolizing dust and viral particles at the same time from that feces,

12:10and then the person can get infected, right? So that's one possible route of exposure. This virus can also survive stomach acid and potentially infect you if you ate food that's contaminated with, say, little bits of rat poo. The World Health Organization estimates that worldwide, thousands of people get Hantavirus every year. But they're usually infected with a version that's less deadly than the one on the cruise ship. And we think that the vast majority of these infections worldwide

12:43come from direct contact with, say, rodent feces. But with the outbreak on the cruise ship, something different seems to be unfolding. So we think that maybe the first infection, Patient Zero, got exposed this way that we've just described, through aerosolized rat crap dust. Here's Neil again. So we don't know for sure how the first person got infection. Right now, the leading theory is that this person got infection while in Argentina birdwashing.

13:18And birdwashing is a very safe activity. But somehow they might have interacted with the feces, for example, of a rodent or rodent urine. Maybe got a bite from a rodent, but that's less likely. And then they got infected. But this is, right now, working theory. But it's highly plausible. Now, one or two people getting Hantavirus directly from breathing in rodent poo or pee, this is not surprising. Because, like we said, Hantavirus is around rodents in a lot of places, including Argentina.

13:49What's weird is that most of the time, when someone gets Hantavirus from a rodent, it stops with them. Most types of Hantavirus cannot spread from person to person. Except the version of Hantavirus that showed up on the cruise ship. It's called the Andes virus, and it can. Andes virus is the only Hantavirus that we know of that spreads from one person to the next. And that is probably exactly what happened on the cruise ship.

14:21And something that's worrying a lot of people right now is that we might not know everyone who's been infected. Because this virus, it can hang around your body for a while before you start showing any symptoms. Producer Michelle Dang asked Professor Michelle Harkins about this. Right after someone breathes in that dust with the Hantavirus from mouse poo, what happens next? They may just go on their merry way, and then there's an incubation period.

14:52And unfortunately, it can be from one to eight weeks. Typically, we see people within about two weeks afterwards, but there are studies showing that it can last up to eight weeks. Eight weeks? That means, theoretically, some of the people who were on the boat and then left without being quarantined could be infected right now. Wandering around, breathing, coughing, listening to podcasts. So after the break, could this lead to the next pandemic?

15:26Coming up.

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Assessing the Risk

18:14Welcome back today on the show. Hunter virus, how freaked out do we need to be? So here's where we're at right now. We know that this virus has the potential to spread from person to person. And now the question is, how quickly can it spread? Could this lead to the next pandemic? And to find out more, we called up Professor Anne Sheehy, a virologist and immunologist at the College of the Holy Cross in Massachusetts.

18:46She's a friend of the show. We've had her on before. And Anne told us that when she heard about this Hunter virus outbreak... I wasn't happy. So as a virologist, you never like hearing about a virus that is doing something unusual. On top of that, she was like, and it's happening on a cruise ship that's traveling all around the world with passengers from all around the global community who are then going to disperse. That's not a good setup.

19:16You're like, oh, no. Oh, no. I don't want my virologist saying, oh, no. But don't worry, because by the end of this episode, you'll be thinking, oh, yes, because you'll know more science. And that's always great. Okay. So as we mentioned, this version of Hunter virus that's roaming around the cruise ship is the only one we know that can transmit from person to person, which makes it different to the one that we heard about from the doctor, Michelle,

19:48which was called Sin Nombre. So Anne told us that to understand what makes the Anders version capable of spreading, we can compare the two. So let's take Andes versus Sin Nombre. So if you were to look at those two haunted viruses, they're pretty highly related. But there's regions that are a little bit different between Sin Nombre, which doesn't spread human to human, and Andes, that does. One difference is in a protein that sits on the outside of the virus and helps it to break into cells in our body.

20:20So for coronavirus, for analogy, we think about spike, right? The spike protein. So on Andes virus, instead of they don't have spike, we call it glycoprotein, so GP. If you think about the cells in your body, like a house with a tidy little door, GP is the key that allows Hunter virus to open that door, break into our cells, and infect us. So these GP proteins are a little bit different on Andes virus. And the consequence is, at least on the sort of infection level, is the Andes virus can infect a wider range of cells.

20:59One study found that the Andes virus also seems to replicate faster in, say, heart tissue, compared to other versions of Hunter virus. So potentially, when you get infected with this Andes version, there's just more viral bits in your body and you have a higher viral load, which could then increase the chance that you go on to infect someone else. And we have examples from other outbreaks that illustrate how this can all play out.

21:30So in Argentina, back in 2018 to 2019, we saw one of the biggest Andes virus outbreaks ever recorded. Scientists think that it started when one person got exposed to the virus the usual way, from a rodent, and then... So went to a birthday party, was feeling symptomatic, but, you know, birthday party, went, and looks like, at that birthday party, probably exposed some other people, but at least two other people that went on to then be involved in social events and spread.

22:02And one of them was the wake of the second person that had died. Yeah, so it spread at the birthday party. Someone died from that infection. And then at their wake, other people got infected. Ultimately, researchers tracked 34 cases and 11 people died. Scientists were able to trace this all pretty well and even test people's blood. And they found that those who had more virus inside their body were more likely to spread the Andes virus to other people.

22:36But what's interesting is that we don't actually know exactly how the virus is spreading from person to person. Is it through coughing, through breathing, through touching? Scientists think that, generally speaking, you see really close contacts to having a higher chance of spreading it to each other, so not just someone you're passing at the supermarket, say. And we know this, for example, from a study on a cluster of people who got infected in Chile,

23:07and they found that sexual contact was a big risk factor for spreading it. And in particular, the paper references deep kissing. That was one of the biggest risk factors they found. And they mentioned deep kissing a lot. They defined it only as exposure to saliva. I guess that is what deep kissing is at the heart of it. But other risk factors in that study were sleeping in the same bed, having sex, and being exposed to semen. And on this point, we found another study from 2023 that tracked a 55-year-old man

23:44who got infected with the Andes virus and later recovered. But get this, almost six years later, traces of the virus could still be found in his semen. Now, I think this is probably going to make this type of hantavirus sound really scary, right? It can spread from person to person. It could stay in semen for all these years. But it's really important to compare how contagious this virus is to other viruses out there that you know and love,

24:18like COVID and measles. So, remember the R0 from the height of the COVID pandemic. This is basically the number that scientists calculate to say if you get disease X, how many susceptible people will you pass it on to on average? And for some diseases, this is super high, like measles, famous for being incredibly contagious if you're not vaccinated. It's estimated that if you get it, you could give it to 12 to 18 other people.

24:49So, but for this hantavirus. So, I think even in the most, sort of the most dramatic outbreaks we have, the R0 is something like two for hantavirus. And if you do any quarantining at all, it drops below one. And once an R0 drops below one, you're not going to, it's not going to be an outbreak. You're not going to get sustained spread. So, I think we're very fortunate that this virus does not spread easily from person to person. This might be partly because hantavirus doesn't seem to hang around in your nose, throat and lungs

25:25in the same way that COVID and influenza does. You know, where a big breath could push out a bunch of viral particles into the air and, you know, maybe infect the person you're talking to. Instead, hantavirus likes to stick around deeper in the cells of our lungs because it really likes those endothelial cells inside our blood vessels. And the fact that this type of hantavirus doesn't spread that easily from person to person is probably why the largest outbreaks that we've had of it have gotten just a few dozen people sick.

26:01Even with this cruise ship outbreak, so far at least, it's hardly gone bananas. In over a month. So far, we've had about a dozen people infected. Now, in this outbreak, it's worth pointing out that while there were early reports that a woman got infected after just sitting on a plane near someone who was on the cruise ship and later died of hantavirus, it now looks like that's not true. The woman on the flight later tested negative.

26:32So here's where we are at. Hantavirus, when you compare it to other scary and contagious viruses, it does not spread easily from person to person. But also, your chance of getting a nasty case of hantavirus from a rodent is also pretty low. Michelle, who's our doctor from New Mexico, who's seen how devastating hantaviruses can be, and she lives in a place where the rodents can be infected with hantavirus

27:04and people every now and then get infected. So Michelle Dang, our producer, asked her, Do you freak out every time that you see a mouse? No, I don't. You know, we actually have done trapping campaigns, and about 25% of the mice in New Mexico carry hantavirus. It sounds pretty high, though. Does that scare you? Sounds high, but our case rates are really low. So it's not a very easy virus to transmit.

27:37And that's like a key thing. It's not easy to get hantavirus. I actually was bitten by a mouse in my house because my cat chased it in. Oh, no. And I tried to catch it and release it. And I was bit by the mouse. And I was like, great, I'm going to get hanta. But I did not get hanta. I got rat bite fever instead. So she took antibiotics for the rat bite fever. She's totally fine. But the broader point is that even though there's a lot of mice scurrying around New Mexico carrying this virus,

28:15pooing and weeing all over the place, and around 2 million people live there, doctors diagnose fewer than 10 cases a year. Anne, our virologist, told us that there might be something else working in our favour here, too. Although we mentioned before the break that hantavirus can have this long incubation period where you can have two months between getting infected and showing symptoms, which, yes, is a long time.

28:45Even Anne said, This is crazy to me. But she also said that unlike COVID, it's not clear that you can actually spread the disease during that time. So here's Anne. It appears at least from the, you know, scant evidence that we do have from well-analyzed outbreaks, it appears that most of the time, transmission, when it's been documented well, it happens and that person is sick. Like, they are visibly sick. They have a fever.

29:16They are not well. And with all of the bonkers stuff on social media that makes this sound so scary, I'm going to give you one more comforting thing. This version of hantavirus that led to the relatively small outbreak on the cruise ship, it's been known to science since 1996, 30 years ago, when Macarena was number one on the charts. And in that time, three decades, it really hasn't mutated,

29:48particularly when you compare it to viruses that have caused pandemics. COVID is a master mutator, much like influenza. That's their bread and butter. That's how they survive. But that's not the case with hantavirus. They looked at the Andes virus that circulated in 2018 in this outbreak, and they compared it to another outbreak that had been documented in 1996, so 22 years previously. And the sequences are virtually the same.

30:21So, put it all together, this virus does not spread easily between people, which is why when an odd outbreak has happened before, it doesn't tend to blow up. And so far, this virus hasn't been mutating to become better at transmitting between people. So, when we asked Anne the big question of this episode, the question that so many of you guys had, is this going to be the next pandemic? Here's what she said. No, no, rest easy. This is not it.

30:52Get ready, because there will be something that's more serious. But no, this is not, this is, you can be okay. But I think we're not going to see too many more cases. And other researchers that we spoke to said the same thing. I want to be very clear. This current outbreak of Andes virus, this hantavirus, is not the next pandemic. No, this is not the next pandemic. So, yeah, it's not the next pandemic. And I know you might be feeling, hey, some of you scientists said COVID would be fine too, and look what happened.

31:27I hear you. But it's easy to forget that COVID was a completely new virus when it just landed on our doorstep in 2019. And at the beginning of the pandemic, scientists were making educated guesses about what was going on and how the virus was going to behave, and they got stuff wrong. With this hantavirus that's causing the outbreak, the Andes version, scientists have been studying it for 30 years. And we know that scary outbreaks tend to be pretty small.

32:01But still, if you want to be careful, if you're cleaning up a space that might have rodent poo, wear a mask. And if you have a friend that just got off a cruise ship, avoid deep kisses. That's science versus.

32:19This episode has more than 80 citations in it. If you want to read more about hantavirus, understand where we get all of our information from. There's a link to our transcript in the show notes. Go check it out. This episode was produced by Michelle Dang, with help from Blythe Terrell, Meryl Horne, Rose Rimler, Akedi Foster-Keyes, and me, Wendy Zuckerman. We're edited by Blythe Terrell. I'm the executive producer. Fact-checking by Diane Kelly.

32:51Mix and sound design by Bobby Lord. Music written by Bobby Lord, Bumi Hidaka, So Wiley, Emma Munger, and Peter Leonard. Special thanks to the researchers we spoke to for this episode, including Professor Glenn Marsh. Science Versus is a Spotify Studios original. You can listen to us for free on Spotify or wherever you get your podcasts. If you are listening on Spotify, you can write a comment. We read them all, and nice ones are very, very nice. It also helps the show to grow, keeps our bosses happy. So write us a nice comment. Also, you can follow us and tap the bell icon

33:24so you get notifications when new episodes come out. I'm Wendy Zuckerman. Back to you next time. You're great at protecting your data,

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