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The Effects of Long COVID on the Fire Service

On this episode of The USFA Podcast, Dr. Denise Smith discusses long COVID, a range of new, returning or ongoing health problems that people experience for several weeks following the initial infection from the SARS-CoV-2 (COVID-19) virus.

Posted: March 16, 2023

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The strenuous physical activities performed by firefighters can worsen the symptoms of long COVID.

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Listen online 37:43

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Estimated 19 min reading time.

Welcome to the USFA Podcast, the official podcast of the U.S. Fire Administration. I'm your host, Teresa Neal. Before we jump into this episode, I wanted to invite you to join the conversation about fire safety. Please email your questions, stories or podcast ideas to

Dr. Denise Smith
Dr. Denise Smith

Please reach out. We’d like to know what topics or interviews you are most interested in. In past episodes we’ve discussed COVID and its many ways it’s affected the U.S. and the world, but more importantly, how it affects first responders. First responders have been our frontline fighters, oftentimes being the first person patients meet.

Because of this, we need to discuss COVID once again. On this episode, we will discuss long COVID. If you are like me, this is a new term. To explain this to us and to discuss how it’s affecting the fire service, we have invited Dr. Denise Smith to the podcast. Dr. Smith is a professor of health and human physiological sciences and the Tisch Family Distinguished Professor at Skidmore College where she serves as director of the First Responder Health and Safety Laboratory.

She’s a senior research scientist at the Illinois Fire Service Institute. Dr. Smith is a leading researcher in firefighter cardiovascular health and has published over a hundred scientific articles and received multiple national and international awards for her work to promote firefighter health and safety.

Teresa Neal

Welcome to the podcast, Dr. Smith. Let’s start with the basics. What is COVID long or long COVID?

Dr. Denise Smith

Teresa, thanks. It’s a pleasure to be with you and a real thank you for taking on this issue. I know full well that people are tired of COVID, and sometimes we’re even tired of talking about COVID. We are eager to have COVID behind us, and let me say that I share that sentiment.

But as you noted, it’s also critically important that we keep our eyes on long COVID or COVID long, or the experience of the long-haulers, which we informally call COVID long. Let me try to answer your first question, what is COVID long? The truth is, is it’s a bit nebulous, and the definition itself has changed over time, but basically, it’s a range of new, returning or ongoing health problems that people experience for several weeks following the initial infection from the SARS-CoV-2 virus, or what we would call as a COVID illness.

Long COVID is a range of new, returning or ongoing health problems that people experience for several weeks following the initial infection from the SARS-CoV-2 (COVID-19) virus.

Now, one of the reasons it’s so difficult to define is there’s such a range of symptoms that an individual might experience. The most common ones — the most common COVID long symptoms — are extreme fatigue or fatigue that is brought on by physical activity, brain fog, shortness of breath. But the truth is there’s probably 50 different symptoms that individuals are experiencing, and for that reason, it doesn’t have a tight clinical definition with 4 or 5 cardinal signs.

Teresa Neal

Kind of like the way that COVID was. For some people, it manifested itself in one way, and for another person, they didn’t have any of those symptoms. They had completely different symptoms, and so maybe they didn’t think they ever had COVID because they didn’t experience the typical symptoms.

Dr. Denise Smith

I think you’re bringing up a great point. It has been hard to get our heads around COVID because it could be asymptomatic, or it could vary tremendously in the severity and the symptoms that presented were wildly different among different people. Some people described it as, “Oh, cold-like symptoms.” For other people, of course, it was devastating, leading to hospitalization, the need to be on a ventilator, and in far too many cases, people didn’t survive.

Similarly, COVID long continues to perplex a scientific community with the broad range of symptoms that it can present with. For some people, it’s a symptom that is noticeable but not particularly troubling. But for many people, COVID long is a cluster of sometimes debilitating symptoms.

Teresa Neal

Okay, so, can you tell us how a cardiovascular researcher became focused on COVID long?

Dr. Denise Smith

Yeah, thanks for that question because, in fact, the last 20 or 25 years in the fire service, I’ve really been thinking primarily about the cardiovascular strain of firefighting and thinking about how the cardiovascular and thermoregulatory strain of firefighting can trigger a cardiovascular event in individuals with underlying disease. So, I spend a lot of time looking at disease states in the cardiovascular system.

Now as COVID came into sight for all of us in the United States, I was reading about it as much as I could, largely for my own health, and just because of my occupational awareness and connection with the fire service and job responsibilities in that area. I was thinking about the burden of COVID in the fire service.

My first thoughts, one of course, to the concern about increased infection among first responders because of the nature of their work and caring for patients. Also, because they live in congregate settings. But more and more as I read about the symptoms — and you referenced this earlier, a wide range of symptoms — as I wanted to understand how a virus could be affecting so many organs of the body and leading to such a strange grouping of symptoms, I started to understand that the lining of the blood vessels were vulnerable.

So, let me say something that I think most people know and haven’t quite put together. The SARS-CoV-2 virus entered the body through the respiratory system and often led to severe respiratory illness. And so, it was called a respiratory disease. But as you think about what happens once the virus enters the lungs and passes through that thin membrane into the blood, the truth is the same receptors that the virus bound to in the lungs, those same receptors are expressed throughout the entire vascular system. So, any organ in your body that receives blood supply, which is every organ in your body, was susceptible to infection through this virus. The same mechanism, the virus bound to receptors, ACE2 receptors, on the blood vessels, and then is able to infect multiple organs.

Teresa Neal

I don’t think we think of it that way at all.

Dr. Denise Smith

Right. I and others, because I was studying and thinking about that vascular endothelium, it’s really right in my research area. But then over the ensuing months, maybe a year into the country really wrestling with all the symptoms, leading researchers from the National Heart Association and others started to recognize how the endothelial lining — and that’s just to say the inner lining of all the blood vessels — was implicated in this disease state.

And if you don’t mind, I’ll tell you some more details that actually might make connections for our audience.

Teresa Neal

Yes, please.

Dr. Denise Smith

This inner lining of the blood vessel, it has these ACE2 receptors that allowed the virus to enter the area, but then that also changes fluid balance. So, in the brain you can have increased swelling in the brain — an edema — which may be related to some of the cognitive changes we see.

You can have changes in the kidneys. You can have changes in the lymphatic system and the liver. But also, this blood lining plays a critical role in inflammation and the production of cytokines. We’ve all heard about how COVID leads to increased inflammation. This is often happening in the blood vessels or because of interactions with platelets and other blood proteins.

It’s a very complicated set of interactions, but as we start to get those interactions in better view, we can better understand what at first was just a dizzying array of symptoms.

Teresa Neal

To be able to start understanding that, you know, it’s not just what we are breathing in; it affects the whole of your body, and that’s why for different people it would have completely different symptoms.

Dr. Denise Smith

Correct. Once we breathe it in, it had the ability to travel in the bloodstream throughout the entire body, of course. And as it did so, it was able to enter different organs, and hence, we see a lot of variability in the symptoms.

Teresa Neal

So, I think you’ve kind of explained what the science of COVID long is, but is there something else that we need to understand about that?

Dr. Denise Smith

Well, I would say yes. I would say we’re just touching on our early understanding of COVID long. There’s been a lot of great research on it. But just like COVID, it takes time for scientists to understand a new presentation of a viral illness.

And some of what we’re seeing with post COVID or long COVID, we have seen with other viruses, and that is, its symptoms persist for a very long time. And yet we don’t have a full understanding of it. I would say this is an area where there will be a great deal more research. In fact, national funding agencies, the National Institutes of Health, have devoted great deals of funding to this, and we need multidisciplinary teams to look at it.

… the current estimates are that somewhere between 10 and 30% of individuals who had COVID will suffer some form of COVID long.

And the reason for such large funding is it’s complicated and it’s new and it’s very consequential because if our first estimates are correct, the current estimates are that somewhere between 10 and 30% of individuals who had COVID will suffer some form of COVID long. Now, on an individual basis, if your risk is only 10%, 20%, maybe that sounds okay.

It’s still a little frightening. We should be worried about that. But if we multiply that by the fact that millions — well, hundreds of millions of people — across the United States alone have been infected with the SARS-CoV-2 virus, an estimate — even a low estimate of 10% — of individuals suffering from long COVID could be devastating in terms not only what individuals are facing, but the ability of the health care system to take care of those people.

So, we must continue to have research nationwide in the general population to understand both the different ways that COVID long can present itself and how it can be effectively treated.

Teresa Neal

So, what should people track? They know that they’ve had COVID and there are some lingering symptoms, or they feel like they just can’t kick something. I — that’s what I’ve heard from a lot of people is, “I can’t kick the fatigue, you know, I’m better with this, but less with this.” And so, what should they be tracking so that they can have this conversation with their doctors?

Dr. Denise Smith

Sure. That’s a great question. And if you don’t mind, even as I try to answer that broad question, I will try to turn it a little bit to not just people, but firefighters in general. Because this is a problem for the entire population. I, myself, have family members who have suffered with COVID long.

I’m very sensitive to it, and it’s a challenge for everyone because the health care system isn’t prepared to address it. And I’m not trying to be critical of the health care system; they haven’t encountered it before, and they have been overwhelmed with trying to respond to the initial COVID crisis and they are now dealing with tremendous staff shortages.

And yet what people are experiencing when they’re trying to get help with COVID long is that the health care system is sometimes dismissive, is sometimes unaware of how best to treat it, and often under-resourced with specialists.

Teresa Neal

Yeah, and I think we have to — maybe I’m just speaking about myself that I’ve seen over the years with my interactions with people, is that we think that when we go to the doctor, that they’re just gonna automatically tell us exactly what’s wrong and then give us the fix for it.

And I’ve talked to many people who get very weary of their doctor because they’re having ’em test for all of these different things. And, and they’re like, “Why don’t they just understand it?” Or after you get a diagnosis said, “Well, they should have known that from the very beginning.” You know, I’ve heard that many, many times.

But I think that we just — we have to understand. I think it opens my mind so much when you say that, that it really affects every, you know, system in your body — every organ, every — everything that for any type of sickness that we have, you know, doctors are doing that checklist, you know, they’re kind of triaging it when they’re trying to diagnose and it hits on 2 or 3, so they go this way and nope, that’s not it. So, then we have to go back and reevaluate again. And I think we have to, especially after COVID, and how much work they had to do and how much catch-up there was for that. I almost feel like we need to give doctors a little bit of grace — doctors and nurses — and let — and try to understand, you know, having a researcher tell us it affects every part of your body.

So we’re not gonna be able to just — you’re not gonna walk in and say, “I have headaches and this,” and they go, "Well, that’s long COVID, and this is what you should expect because ….” And you wouldn’t want them to, ’cause what if you were going in because you have headaches and they said, “It’s just long COVID,” and then you find out it’s a brain tumor or it’s an aneurysm or it’s any of these other things. You know, we have to give that grace to walk us through it.

Dr. Denise Smith

Yeah. I really appreciate that sensibility about how complex the issue is, first with human health. You were talking about human health in general.

Teresa Neal


Dr. Denise Smith

It is not an easy thing to diagnose what’s wrong with an individual, particularly I think about the examples you used of a headache, which could be caused from a myriad of things. Now, I think COVID is particularly complicated for the reasons we’ve mentioned: It’s new to us, we have not studied it for 30 or 40 or a hundred years like we have many other illnesses, and the physicians have not been trained in it.

And all of the time they’ve been trying to treat their patients, they’ve been overwhelmed with patient care, and at the same time, the amount of articles that are coming out on this. I would guess that there are 10 or 20,000 new articles on COVID. Obviously, they’re not reading them all. And if they were, the articles themselves are not consistent because it’s an emerging picture.

So, our physicians have been relying on simple guidance material that’s been coming out, and we all understand the limits of that as we faced simple guidance on masking and vaccinations. Those are really complex issues. I think you’re right. We need to give some grace and leeway and a great big thank you to all of the health care professionals that have been in this and on the frontlines of it, often risking their own health to help take care of patients.

But even as we do that, I don’t wanna lose sight of the tremendous frustration of people who are experiencing these symptoms, and one of the symptoms is itself depression and anxiety. And that — I have not experienced it, and I don’t want to sound like I can speak from firsthand experience, but I can have empathy to understand that if I have been sick, if I have felt achy in every single part of my body, if I can’t engage in daily activities, and this has gone on for months and I’ve seen the doctor 6 times, 8 times, and every time I hear: "Well, I don’t know. Oh, we could run another test. Oh, everything came back normal. Maybe some of this is just in your mind,” I can just begin to imagine the frustration and the burden that that must feel like for individuals who are suffering from long COVID.

Teresa Neal

And especially for some of them that had, you know, severe and traumatic — the work done to bring them out of, you know, these devastating states, left them traumatized to it and that, and so they don’t want to hear it’s all in your head or you are just not getting over it.

There’s so much more to think about than just your initial feeling of what’s going on.

Dr. Denise Smith

Right. It certainly is not a place where we can easily place blame because individuals are not getting the care they should. But I think we can all join hands and say we must find the resources to do better for people who are suffering from these long-term COVID effects.

And our conversation has taken us quite naturally to some of the people who are suffering the most severe cases. And I believe now there is widespread recognition in the medical community that this is real. There are still insufficient resources like multidisciplinary clinics devoted to helping individuals, but we have gotten, I think, more widespread recognition that there’s this need.

There’s another category of people or continuum of people that are suffering persistent symptoms. They’re not debilitating, but the individuals are not fully recovered. They don’t feel right. Now, this is a real perplexing problem for physicians because now you can’t even really treat symptoms.

You might hear, you might believe, you might see, yes, things aren’t right. Yes, you should feel better than what you’re reporting and the symptoms you’re describing of persistent fatigue, malaise, joint pain, sometimes difficulty breathing or whatever the range of symptoms it might be. But now the people are not in some debilitating state, but they are certainly not at normal function.

This isn’t okay. That’s not how we wanna live our life. And again, if I could turn the conversation a little bit to firefighters.

Teresa Neal

Absolutely. That’s where — it’s really where I wanted to land, but I get a little bit ahead of myself, I think.

Dr. Denise Smith

Everything we talked about certainly includes firefighters.

Teresa Neal

Exactly. They’re humans. We’re talking about people, and they are people as well.

Dr. Denise Smith

They are people. But if we — this is an area of vulnerability I see, Teresa, for the fire service, because I know the fire service well, and there is tremendous motivation to return to work. Especially when they know their crews are short-staffed, people are working overtime, and their whole work experience has been you work when you’re tired.

You don’t leave the crew because you’re tired. And so, when there are these ill-defined symptoms, and let me just say a few more of them because different people will connect with different ones. There’s this sense of: “I just don’t have the normal level of fatigue. I tire more quickly, but I can do some things. Sometimes I have an upset stomach; I’m not wanting to eat as much. I’m gaining weight more readily; I can’t figure out why I’m gaining weight. Sometimes there’s chest tightness or pain. Sometimes I even feel palpitations.” There are — again, there’s a list of 50 that are commonly looked at.

I don’t wanna just read a list of 50, but if any of these symptoms feel like they’re persistent to you or in a — they’re occurring more often, it is worth asking yourself, “Could I be suffering from symptoms of prolonged COVID?” And I am gonna take just a sidestep here to say, when people first begin to ask themselves that question, many people wanna dismiss it because they will say, “I did not have a severe case of COVID.”

Teresa Neal

I wasn’t in the hospital on ventilators. I — you know, it wasn’t severe.

Dr. Denise Smith

Right? And so, they think if I did not have a severe case, then I cannot have COVID long. I would like to dismiss that myth because COVID long is more likely if you had severe COVID, but it’s happening in everyone regardless of the severity.

And so, one study I read, they took people who had mild COVID, there was no hospitalization, it was all an outpatient group with, quote, mild COVID, and in that large cohort, 30% of participants had long-term symptoms. Now, long-term symptoms can be severe or not severe. And again, I would apologize to the audience; I know that this is complicated, but indeed, this viral infection and all of the aftermath of it, both acutely and months, even years after, is complicated in terms of personal health and the health care community and for occupation specific. And so once again, pulling our conversation back to firefighters.

The firefighters who had a mild infection to moderate infection, but don’t think that they would be vulnerable to COVID long, should reassess the symptoms. Is this tiredness the normal tiredness of, you know, you had another 24-hour shift, you’re not getting all the sleep we want you to, or is the fatigue different?

If there’s new hypertension, could that be related? If it’s harder to lose weight. If you’re feeling less motivated to do the same things. If you sometimes find yourself in, oh, a brain fog, maybe it gets later, later in the day. Maybe you’re having trouble with recall. These are all symptoms that might suggest that firefighters are suffering from COVID long.

And I have a particular concern for the fire service because, as I said, firefighters will push through a lot. I can well imagine a firefighter with COVID long that’s going to the station, in part because they’re motivated to do it, in part because they wanna get out of the house, in part because they see it as a personal resilience to push against fatigue.

And I know this: Many days it would be fine. Many days if you’re doing routine things around the fire station, maybe even an inspection — but I worry what would happen to these firefighters should they get a very difficult call. Because one of the things we know about COVID long is that many of the symptoms are exacerbated by exercise or strenuous exercise.

We also know that COVID long can be associated with clotting disorders, pulmonary embolism, microthrombi in the kidneys or blood clots in the heart. And this is a very potentially — and again, I wanna be careful here — these are potential concerns because we don’t actually have the data. But I know that firefighting increases blood’s clotting potential. I know that COVID long increases blood clotting potential, and so I want us to have our eyes wide open and be looking for potential problems so that if they do occur, the fire service itself sees them early, recognizes them, and we don’t have individual isolated instances where firefighters don’t know where to turn. But rather we recognize it: “Oh, that could certainly be part of the lingering effects of COVID long that we have to find mechanisms to address.”

And some of that’s better research on the medical side. It may also require changes to policy on the occupational side.

Teresa Neal

So, everything you said, it’s a huge health care concern for our future and a health care concern for our firefighters, for our fire chiefs as they have their people coming back into work.

What do you see, I guess, as affecting the fire service as a whole?

Dr. Denise Smith

Well, my concerns — my concerns are that we will have a percentage of firefighters with symptoms so severe that they can’t return to work. Personally, as I’ve spoken to departments around the country, this is not a huge number, and so, at first, I feared it could be a large number and that backfill would be a tremendous problem.

I’m understanding now from most of the fire chiefs and departments I’ve talked to: This is not a staggering problem. Many departments, particularly if you have many members at all, have members that are — have some symptoms or they know of one person who required months, but it’s not a tremendous number, so it hasn’t completely overtaxed the system.

But I do think that we are in a position where likely many members, many firefighters are back — volunteers or career — back to returning to fire calls. And I think we need to be attentive to if there is some cumulative danger. We know that firefighting taxes the cardiovascular system. Is there a new vulnerability in individuals who are returning to work after a COVID infection?

Is there a time limit on that? Does it depend on other existing cardiovascular disease risk factors? I think we need both more research from researchers in the fire service who know the fire service well and can work alongside them, and we just also need all of those in the fire service who have responsibility for health and safety.

So, from your chiefs down, your health and safety officers, those who serve on health and safety committees, and those who are themselves champions of health and safety, we just need to have our eyes open for a potential vulnerability.

Teresa Neal

And what do you — what would you think that firefighters and emergency medical service members should do?

What is their step in this? I know you said talk for those responsible for the health, but the individual person, what would they be doing? The individual firefighter, because as you’re talking about, I mean, I saw even more that cardiovascular and, you know, that interchange and how important it is.

And it kind of frightened me listening. I don’t know if it frightened any of our listeners when you’re talking about could you have increased, you know, issues. And I’m thinking, well, firefighters already have that increase, and now we’re adding another increase of cardiovascular. I mean, it’s, you know —

Dr. Denise Smith

Yeah, a potentially increased risk. And thanks for asking that because, I mean, this is the fire service. Your voice just resonates with me because I know it’s what they’re gonna say. Okay, what do you want me to do? Okay, I heard you. You want me to be more aware. What else? Well, I think with this awareness, the first thing I’d like to say is to individuals.

If you’re a firefighter and you heard some part of this that makes you wonder, “Hmm, I wonder if those symptoms that I’ve been experiencing really could be related to COVID,” then it’s really worth you tracking them and making sure you can articulate your symptoms to a health care provider.

Now for all firefighters, there’s never been a more important time to make sure that every firefighter is getting an annual health exam, and this should be provided by someone who’s familiar with the work of firefighting.

So, during that physical exam, medical evaluation, it’s really important that you could convey any of these symptoms, whether it’s: “I’m having brain fog or trouble thinking. I’m having — I’m experiencing depression in a new way. The weight gain, the soreness, the fatigue, the fatigue with exertion.” All of these things you would definitely want to make sure that you were conveying to your occupational health provider because they will understand the work you do in a particular way.

Now, one of the challenges — and I’m sorry that I keep pointing to challenges and unknowns, because I know that’s frustrating. It’s frustrating for me as well. But, but one of the unknowns is what will happen once you convey these things, or you track your own symptoms because the health care system itself doesn’t know.

But we can see some directions that this might lead. I think if a firefighter is reporting symptoms to an occupational physician while they do a medical evaluation, there’s an opportunity to do some more advanced testing. And this will catch some cases and allow us to intervene in places where we can address symptoms or some underlying problems.

So, let me take the cardiovascular system as an example. There can be some cardiovascular changes that are transient. There can be inflammation in vessels that this can be treated, but there can also be damage to the heart. Now, most all of this would be unseen. But if firefighters are being diligent about tracking and reporting their symptoms, raising the awareness, it might be called level of suspicion for health care providers, then they can order additional testing and find more components to treat.

I wanna leave you with the caveat. We still don’t know perfectly how to treat all the components of COVID, but we can treat some of it. And we put ourselves in a much better position when firefighters have a level of awareness that allows them to talk intelligently with their health care providers.

And the last thing I just have to say, if you’d give me one more moment here.

Teresa Neal

Yes, please.

Dr. Denise Smith

The medical evaluations, making sure that our firefighters have medical evaluations, has always been important. It’s important for cancer screening, behavioral health screening, cardiovascular screening, and now understanding how COVID may intersect with any or all of these because COVID is certainly disrupting the immune and hormonal system.

And so, there could be intersections not just with the cardiovascular system, but with the major health issues facing the fire service. So that occupational exam is more important than ever. But it is also critical that firefighters who recognize symptoms in themselves certainly check with their primary care physician.

Do not wait 8 months or 2 months or 10 months until your next medical evaluation. That’s a basis we must have for all firefighters. But if you’re recognizing the potential that these symptoms apply to you, I’d urge you to see a primary care physician and see if there’s follow-up care that can help get you back closer to normal more quickly.

Teresa Neal

Thank you so much for being with us today.

And fully taking care of a problem is what the fire service does. The fire service doesn’t leave a smoldering fire, and we can’t leave COVID too quickly despite our eagerness to do so.

Dr. Denise Smith

Well, it’s a joy, and once again, I appreciate all the work that USFA does to support the fire service, and in particular, I appreciate you bringing some attention to a topic that many of us would like to put off to the sides, but really situational awareness is a key for the fire service.

Teresa Neal

Well, I have to say thank you and, also, that I wanna have you back to talk about cardiovascular health. I’ve heard you speak recently, and I was — you explain it so well. It can be, you know, sometimes when we hear researchers or doctors talk and it goes in one ear, out the other — big words. But you always bring it down and explain it better than even if you use the big words, you know, you’re a plain language advocate and you make sure that we understand. And so, I wanna have you back in the future for cardiovascular health as well.

Dr. Denise Smith

Well, I appreciate that anytime I’m with you and doing whatever I can to help support the firefighters across this nation who are doing so much for us. I’m happy to do it anytime. Thank you again, Teresa.

Teresa Neal

Thank you.

And so, as I mentioned at the beginning of the episode, you can join the conversation about fire safety by emailing your questions and sharing your stories to

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