The dormant viruses in all of us may help explain long COVID

Virtually every human on Earth has a slew of different types of dormant viruses in our bodies. They are remnants of past infections and are—generally—harmless. Unless they wake up, which can be triggered by extreme stress or something that severely compromises the immune system. But now, through a unique study on the immune systems of astronauts, scientists are considering broadening their ideas about what can wake up our dormant viruses…and learning what all this has to do with long COVID. If you liked this episode, check out our episodes on a universal flu vaccine http://lnk.to/K3HMKr and what scientists got wrong about covid http://lnk.to/oRdSAL. Support public media with NPR+ and enjoy perks for over 25 podcasts like this one. This show’s perks include sponsor-free listening. Learn more at plus.npr.org http://plus.npr.org/. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

• 0:00Speaker 00

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• 0:21Speaker 01

  Hey, you. Yeah, you. Listen, I've got news. Don't worry, it's not as scary as it sounds, but you probably have a dormant virus living inside of you right now. Whether that's the virus that causes chicken pox.

• 0:35Speaker 02

  Before the vaccine, 90 to 98% of people carry this virus.

• 0:42Speaker 01

  Or other viruses in the herpes family, like the roughly 95% of adults who carry Epstein Barr, which causes mono, or the roughly 60% of adults who have cytomegalovirus.

• 0:53Speaker 02

  So these are extremely common viruses that you and I carry, multiple of these viruses in dormant state.

• 1:01Speaker 01

  Akiko Iwaki is an immunologist at Yale School of Medicine, and she says this has been known for a really long time. It's also known that some of these viruses can reawaken when someone is severely immunocompromised. But in 2019, thanks to a review of research that looked at astronauts' saliva, scientists were able to learn two new things about these dormant viruses. One, that they could reactivate in totally healthy astronauts just from the stress of spaceflight.

• 1:31Speaker 02

  Like, more than half the astronauts that were tested had evidence of reactivated viruses, such as Epstein Barr virus, cytomegalovirus, and others.

• 1:42Speaker 01

  Others, like the virus that causes chicken pox. Multiple viruses reactivating, all in the same person. That was the second shock, that so many could reactivate all at once, even if the astronauts didn't seem sick.

• 1:56Speaker 02

  It really teaches us that immune system is likely, you know, key in surveilling and ensuring that these dormant viruses remain dormant. And when you lift that with all the different stressors, these viruses can come out and potentially infect other people.

• 2:13Speaker 01

  And while most of us don't have to deal with the stress of being launched into space or living in zero gravity, Akiko says the NASA study suggests something really important, that there could be big stressors down here on Earth that we've just been overlooking.

• 2:29Speaker 02

  Kind of puts our mind about, like, what other stressors might be doing this on Earth, right? So we know that when you're under stressful conditions, or when you have another infection, the immune system's ability to keep these dormant viruses in latent state, you know, is compromised. And we've seen this during COVID, we've seen this during other infection conditions. So it really teaches us that, you know, these are potential drivers, right, that can reactivate herpes viruses.

• 3:02Speaker 01

  So today on the show, what happens when dormant viruses wake up? And what it could mean for conditions like long COVID? I'm Nate Rott, you're listening to Short Wave, the science podcast from NPR.

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• 4:41Speaker 01

  So, Akiko, we mentioned a handful of dormant viruses, the virus that causes chicken pox, Epstein Barr. Are there other viruses that hide out in our systems after we recover from them that we haven't talked about?

• 4:52Speaker 02

  There are other viruses, like, for example, HIV. HIV also can become latent within T cells, and they can stay dormant for years until the immune system no longer is able to contain them. So this is sort of the age stage. But yeah, there are other viruses that can become dormant. But even those viruses that are not known to have latency stage, now we are learning that they can become persistent and potentially have a dormant, or at least quiet, stage that stays in the body, and they can sort of become activated upon stress and immunodeficiency.

• 5:33Speaker 01

  Can you explain why some of these viruses stick around while others don't?

• 5:39Speaker 02

  Yeah, these viruses that we're talking about, the herpes viruses, they're really ancient viruses that have evolved together with humans, and they have figured out exactly what to do to turn off their viral signatures so that the immune system doesn't attack them anymore when they're in latency stage. And when there is stressors and when there are reactivating event, they can, you know, transmit the virus to another person without making the host debilitated. And also, these viruses, even during asymptomatic stage, they're shedding constantly. For example, if you take a saliva from any healthy person, you can find shedding herpes

• 6:21Speaker 02

  viruses without any symptoms, and that can transmit to another person.

• 6:26Speaker 01

  So asymptomatic, but still contagious?

• 6:29Speaker 02

  Yes, exactly.

• 6:30Speaker 01

  Evolution, wow.

• 6:34Speaker 02

  Viruses evolve much faster than us, so, you know, they really figure out the immune system. In fact, it's very interesting, if you study the genes from these viruses, we learn about how the immune system works, because they've figured this out molecularly. And we're catching up, the immunologists are catching up and learning about the immune system, which the herpes viruses have already figured out. So it's like, you know, arms race.

• 6:59Speaker 01

  Yeah, a Cold War, literally.

• 7:02Speaker 02

  Exactly.

• 7:05Speaker 01

  Okay, so I had chicken pox as a kid. I was pre-vaccine age, not to date myself. So just so I understand correctly, that means that I likely have that virus still hanging out inside of me, just hanging out, right?

• 7:18Speaker 02

  Yes, very likely.

• 7:20Speaker 01

  Well, thanks for the good news.

• 7:25Speaker 01

  I'm curious, and like, what could cause it to reawaken? Is it, would it just take my immune system crashing out?

• 7:31Speaker 02

  Yeah, it could take your immune system crashing out. It could also be other infections, like, for example, severe COVID-19. Things like that can reactivate shingles, and also age. So, you know, VZV can reactivate in older adults, and that's why there is vaccines available for VZV against shingles that older adults can take to prevent that reactivation. And it's highly effective and highly recommended.

• 8:04Speaker 01

  Yeah, I want to ask you about COVID, Akiko, but I'm curious, like, even prior to COVID, this astronaut research, how did that change the thinking about what can reactivate dormant viruses?

• 8:16Speaker 02

  Yeah, so there's many literature linking stressors, like immune suppression, or aging, or physical or mental stress can reactivate these viruses. That study with astronauts showed that when you combine all these stressors together, you can really reactivate all these viruses all at once in people.

• 8:41Speaker 01

  Yeah, I mean, you know, most of us aren't going to go to space. I'd love to, but I don't see it on my bingo card this year. But are you saying that even if I'm just really stressed out, not sleeping well, because I have a two-year-old kid, that could also reactivate a virus?

• 8:58Speaker 02

  Well, it depends. Oftentimes, these stressors aren't just a daily stress that you might have being a parent or whatever. You know, it could be more traumatic events, or accidents, or, you know, severe infections, or immune-suppressive drugs, or other things. So I wouldn't, you know, worry about being stressed out about stress itself, causing reactivation. And also, you're young.

• 9:24Speaker 01

  Self-perpetuating cycle of stress, right?

• 9:27Speaker 02

  Exactly. So, and younger people like yourself, it's unlikely to have shingles with mild stress, whereas, like I mentioned, older adults tend to have a much more likelihood of, you know, getting this shingles and reactivation of VZV. So you can prevent that with a vaccine.

• 9:46Speaker 01

  News you can use, right there.

• 9:49Speaker 01

  So, Akiko, you research long COVID, which the Centers for Disease Control defines as COVID symptoms lasting longer than three months after the initial infection.

• 10:00Speaker 01

  Is that different from what we're talking about with these other dormant viruses? Or does COVID kind of get lumped in with them?

• 10:06Speaker 02

  So emerging evidence is now showing that herpes viruses like Epstein-Barr virus infection is linked to many things, including long COVID. One very clear example is there is a very strong link between EBV infection and mononucleosis and multiple sclerosis. And now there's a lot of evidence showing that there may be a mimicry between EBV antigens and self antigens, and that's what's driving immune attack of your own cells within the nervous system. So there seems to be a very strong link between EBV and multiple sclerosis and similarly EBV and lupus.

• 10:48Speaker 02

  And now we and others are seeing, you know, long COVID being linked to EBV reactivation as well. So this is possibly one of the root causes of long COVID.

• 11:00Speaker 01

  So what you're saying is that what we're finding is that COVID can maybe reactivate some of these Epstein-Barr viruses and other viruses. And that might actually be what people are feeling when they're suffering from long COVID.

• 11:15Speaker 02

  Right, exactly. And that's one of the hypotheses. And there are, you know, other hypotheses that that may have an overlapping mechanism, such as persistent COVID-19 virus presence, as well as autoimmune diseases. Like I mentioned, EBV and autoimmune diseases are highly linked. And we know that some people with long COVID develop autoimmune diseases. So this may all be linked together. We don't know what comes first and what drives the next stage, but that's sort of the picture we're seeing.

• 11:49Speaker 01

  It's so interesting. I have family members who suffer from long COVID.

• 11:55Speaker 02

  I'm sorry.

• 11:56Speaker 01

  And they've been, yeah, it's terrible.

• 11:58Speaker 02

  It's terrible, yeah.

• 12:00Speaker 01

  And just having to go down the rabbit hole of trying to follow the latest research and get on Reddit forums and everything, trying to find answers to, you know, the many questions that they have about what's causing them to feel so crummy.

• 12:15Speaker 01

  And I'm curious if you feel like we are getting answers there, or if there's still more that we don't know.

• 12:23Speaker 02

  Yeah, we as a field is making very good progress in research, but there's so much that we still need to know about what causes long COVID. And these dormant viruses may be playing a role in there, but there may be others. And yeah, the more research is needed.

• 12:41Speaker 01

  What are the big questions that you have? Like, if you had unlimited funding, unlimited research capacity, where would you take that?

• 12:51Speaker 02

  Yeah, so an exciting area of study is how these chronic viruses can potentially act on the nervous system. So there is inflammation that happens in the brain and peripheral nerves as a result of reactivating viruses, or even with the SARS-CoV-2, the COVID-19 virus, that could persist in different tissues throughout the body. So an emerging, exciting sort of area of study is to really link how the primary infection then leads to the reactivation of viruses that could then turn on autoimmune diseases

• 13:32Speaker 02

  and so on, and ultimately lead to the conditions that people are suffering. And to be able to identify who has which of these mechanisms ongoing is absolutely key, because then we can target with existing drugs, many of these, you know, causal pathways. Just speaking of existing drugs, I think we really need stronger and more effective antivirals for these latent dormant viruses. We don't really have a good sort of tool to fight off these latent viruses.

• 14:07Speaker 01

  It sounds like what you're describing is kind of like a domino effect, where one thing triggers another, which triggers another, which triggers another, which makes it so hard to treat, right?

• 14:16Speaker 02

  Exactly. But if we can identify which domino pieces have fallen in which patient, right, then we have a way of targeting the right treatment to those patients. So what we need is, you know, the microscope, that kind of identify the fallen dominos.

• 14:33Speaker 01

  So I want to step back, because we're talking about dormant viruses, which you've already said likely all of us have. Is this something that people should be trying to get rid of or controlling, or should just know that they have?

• 14:48Speaker 02

  For most healthy young adults, these viruses don't really pose a threat unless you're challenged with things like COVID, right? So it's not that, you know, we have to find an urgent way of getting rid of these viruses from everyone, but like I said, these viruses are now linked to so many different diseases. It would be great to develop vaccines against these herpes viruses. We have a vaccine for chickenpox, but we don't have vaccines for the other herpes viruses.

• 15:22Speaker 01

  Well, Akiko, thank you so much for taking the time to talk to us about this. It's super interesting. I learned a lot.

• 15:28Speaker 02

  Thank you so much, Nate.

• 15:32Speaker 01

  If you liked this episode, check out our episodes on a universal flu vaccine and what scientists got wrong about COVID. This episode was produced by Burley McCoy, edited by our showrunner Rebecca Ramirez, and fact-checked by Tyler Jones. Kwesi Lee was the audio engineer. I'm Nate Rot. Thanks for listening to Short Wave from NPR.

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