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Get Infectious [Podcast]

Understanding Epidemics

Disclaimer: This podcast does not substitute for medical advice from a clinician.

About This Episode

Swine flu, COVID-19, MPox. What might be next? Our hosts chat with an infectious disease physician to learn about epidemics, what causes them and what we have learned from recent ones.

Karen M. Krueger, MD, is a Northwestern Medicine infectious disease and internal medicine physician.

Karen M. Krueger, MD
Infectious Disease

About the Get Better Podcast

Living a healthier life is a journey with no final destination: You can always get better.

Susan Russell, MD, Khalilah Gates, MD, and Michelle Prickett, MD, are three pulmonologists at Northwestern Medicine who help people get better from critical illnesses. They are also lifelong friends and lifelong learners who want to get better from head to toe.

These three physicians will learn alongside you as they interview other Northwestern Medicine experts about health and medicine topics meant to help you achieve better health.

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Russell [00:00:02] Let's get stronger. 

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Prickett [00:00:04] Calmer. 

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Russell [00:00:20] Today we're talking about infectious diseases, which still remains something very important in our day-to-day lives. This covers a lot of things, but in the last year or two, people in particular have been talking about COVID, about, what is a triple-demic RSV? And I just — I would love to have a gut check about what these things are and why we think they're important. 

Prickett [00:00:44] And how we can address them. I think the science is improving. And all the time.   

Gates [00:00:49] You know, we have a lot to learn as a society, as a community, after dealing with all of these various viral outbreaks, epidemics, pandemics. And so, what can we learn so that the next virus that comes around and creates another pandemic, we don't repeat the cycle? So, I think there's so much to discuss. 

[00:01:17] (music interlude). 

Russell [00:01:17] Today, we're talking about all of these things — pandemics, epidemics and everything in between — with Dr. Karen Krueger. Dr. Krueger is a Northwestern Medicine, infectious disease and internal medicine physician. She's here to spread the word about the things that spread, like viruses. Welcome, Dr. Krueger. 

Krueger [00:01:32] Thank you guys so much for having me. I'm excited to talk about everything infectious diseases today. 

Gates [00:01:37] I wanted to kind of start off by just having you reflect about where we've been and where we are today. The CDC has a pandemic timeline that's pretty helpful that goes over how COVID began. Any thoughts that you want to share about that time of March 2020 and how you felt when all this was beginning and how you feel about it today? 

Krueger [00:02:01] So kind of on a personal note, I came back from maternity leave in February of 2020, so in my postpartum brain fog, I had no idea what was happening. I was like, “What is this virus everybody is so excited about?” And then when we got our first cases here in Chicago, you guys probably saw kind of the same first COVID cases that I did here at Northwestern. I mean, it was a really, really rude awakening. And I remember how scared I felt seeing those really severe cases and not knowing what we were dealing with and what patient populations it was going to affect most and what numbers we were going to get. I remember as we opened up additional COVID ICUs, which I'm sure you guys were very involved in, and additional COVID wards. And at the beginning, as infectious disease specialist, we are rounding on every patient in the hospital with COVID. There was just, again, that fear and then a lot of uncertainty. I just remember getting asked questions by family, friends, patients, other healthcare workers, and not knowing what to tell them, not knowing how to answer those questions and really predict where we were going. That was a really, really tough period, I think, for everybody, really a remarkable time to kind of look back at and think what we made it through. It's been amazing where we've come over the last few years. We have learned so much about this virus. We have learned ways to prevent transmission. We've gotten to a point where the virus seems to be less severe in terms of the disease it's causing. We have a lot of immunity. We just understand so much more. So, we kind of have all these tools and a much better understanding and things aren't totally back to normal. COVID is still there. There are still people who are sick and dying from COVID. So I don't want to minimize it. But we're really at a place where, you know, so much of our functioning in society is kind of back close to what it was pre-COVID-19. 

Prickett [00:03:54] So Susan and I have trained together pretty much since we've been doctors. And I will tell you, we went through H1N1, we went through Ebola. When COVID hit, it was probably our first pandemic. And I found myself with those first cases in the ICU, and it was just unlike anything that I had seen in my career. So, do you mind just telling us a little bit about the differences between an epidemic, a pandemic, when things are endemic and kind of what that means and how we define those? Because I think even for those of us that have been doing this, I wasn't familiar with all the terms. So it’d be helpful just for kind of level setting. 

Krueger [00:04:31] So I'll start with endemic. So endemic is when a disease is constantly present and kind of regularly occurring within an area. So, an example, in a country in Africa that has malaria, malaria is endemic. It's expected that you may or may not, depending on season and exposure, come into contact with a mosquito that carries malaria. An epidemic is when we see an unexpected increase in the number of cases of a disease in that specific geographic location. Just thinking about a change in ecology, so people coming into contact with different bacteria or viruses, or could be a new pathogen, a change in an existing pathogen. And again, just maybe introduction into a new population that doesn't have immunity to that. And we can kind of see the cases go up. And then a pandemic is really when that kind of epidemic starts spreading to a larger geographic region. So, crossing international borders and really getting to a scale where it's kind of out of control and really no longer able to be easily contained at that point. And a lot of times we use specifically the term pandemic when we're getting to the point where there is large-scale social disruption and a lot of morbidity and mortality associated with it. 

Russell [00:05:43] So do you think it's, it's right when people say either the pandemic is ending or the pandemic is over when it comes to COVID? 

Krueger [00:05:53] Yeah, I think we're probably transitioning from what will be like a pandemic stage to an endemic stage. So COVID-19 isn't going anywhere right now. It's still out there, it's still circulating, people are still getting infected from it. But we definitely have gotten to a place where we have a lot of tools that we know are effective to minimize spread and then again, try to reduce morbidity and mortality, those really severe outcomes associated with it. So, I think we're kind of in that phase where we're kind of transitioning from that out-of-control spread to more “COVID is going to be a part of our life and something we still have to deal with,” but not on the same kind of emergent level that we did a couple of years ago. 

Prickett [00:06:34] So really, pandemics are not a new thing. COVID is probably the biggest one in our lifetime so far. 

Krueger [00:06:40] We've had many pandemics and epidemics in the past. Viruses and bacteria are going to keep circulating and causing issues as they interact with, with human and other animal hosts. What we actually have more of in our pocket from the COVID-19 pandemic is really all the scientific advances in terms of rapid testing and really being able to understand the genome, the DNA of the different viruses and bacteria we're looking at. And vaccine development obviously has really changed how we're able to address major infectious disease threats. 

Russell [00:07:13] Do you think that we'll be bringing more of these kind of advances in diagnostics into the home, like how people are able to test themselves for COVID at home? Do you think that's going to translate to us also being able to test at home for the flu or RSV or other things more easily? 

Krueger [00:07:29] Yeah, I would love that. I think, you know, especially with a lot of individuals, it's hard to necessarily like get in for a test and it can be really helpful and empowering to kind of know what virus you're dealing with, especially like when we saw a ton of influenza, a ton of RSV and we still had COVID-19 circulating. So, to think about what virus somebody may have and, again, how long they should be staying out of work or out of school, but without having to get in and arrange for testing and things like that. So, I would love — again, we want the test to be fairly accurate and we still want people to be in communication with their healthcare providers. But I think the more we can kind of empower people, the better. And I think especially for, you know, less industrialized nations, I think more kind of rapid point-of-care testing for respiratory viruses, but also a lot of the other kind of diseases that circulate around the world would be amazing for us in terms of surveillance of these diseases and, again, early diagnosis and appropriate management. 

Prickett [00:08:27] What are some things that we can do, either as a society or as individuals to help decrease our risk of not only the current pandemic, but kind of all comers? 

Krueger [00:08:37] First of all, it's really important that there are surveillance systems set up, especially for diseases that are felt to be high — likely to cause potential epidemics and pandemics in the future. So, for things like influenza, specifically, is very highly monitored. How those strains are changing throughout the year and again, with the coronaviruses and then other arboviruses like mosquito-borne illnesses like dengue, Zika, chikungunya, that have a really high burden. So, it's really important to kind of have active surveillance going on. And then, again, really quick responses globally when we see something that is atypical, more cases than is seen on average in a certain location of any disease or again, like with COVID-19, the reporting of these kind of atypical, severe pneumonias that quickly kind of got identified as this novel virus. So not only is there surveillance, there's also, you know, trying prevention. And so, again, that can be through vaccine initiatives. And that needs to be done globally, especially in these countries where we're seeing more of these diseases. Development and access and distribution are going to be big, important components of that as well, too, as we see progress being made with like dengue vaccination, for example. And then, you know, I think we do need to think about factors like how humans are encroaching on certain areas of nature and coming into more contact with different animal species and different insect species and how that affects the life cycle and the potential interactions and developing many of these infections as well, too. People are also concerned with climate change, whether that may affect where are these mosquito populations that carry a lot of diseases could end up going. Infectious diseases don't respect international borders and really, because of that, it just, it makes it so easy for things to spread a far distance compared to what we would have seen 100 years ago, 200 years ago, just living in a completely different type of society. So I think those are the things that, you know, we need to encourage our governments and other governments and in collaborative efforts to try to prevent and surveil. And then again, really jumping on top of things, taking things seriously and thinking about management when we do get to the point where disease starts spreading. On an individual basis, probably the best things we can do are staying vaccinated. So, we see like when vaccine rates of measles starts dropping, we start seeing little pockets of measles pop up places, especially if you're traveling to a place that has an active outbreak. Same thing with polio. We're getting transmission of polio pop up here and there again. So really encouraging people to stay up to date on these, what we classically think of childhood immunizations. Because once you drop below that herd immunity level, you're going to be prone to having more of these outbreaks. Kind of beyond that, I think a lot of it kind of depends on what disease we're talking about again. So, you know, if you're traveling to a country thinking about mosquito precautions and things like that, so you don't bring it so you don't get sick, more importantly, really, so you're not bringing things back that could potentially get transmitted locally. We could see people come have the same mosquitoes in Miami as they do in places in the Caribbean and South America. And so you can get theoretically a local transmission of some of those mosquito-borne illnesses, just as an example, and then again, potentially altering your behavior. So, like when we see an outbreak of mpox, for example, we can kind of say like here are the riskiest things that you can do to acquire it. And maybe while the transmission levels are really, really high, we want to adjust your behavior for a period of time until those levels come back down in the community. And then I always tell people, stay away from exotic animals. There was that Illinois prairie dog outbreak of mpox back in, I think it was 2003 or something like that. It was all these people getting prairie dogs that were infected with mpox. And that was how our we had our first U.S. epidemic of it. Well, stuff like that can have rippling consequences as well, too. 

Russell [00:12:26] And just to clarify, mpox, is monkeypox, correct? 

Krueger [00:12:29] Yeah. Yeah. So for anyone who isn't aware, the name was actually recently just changed from monkeypox to mpox by the WHO. So that's what the CDC and other organizations are recognizing as well. 

Russell [00:12:41] I always thought it was fascinating how infectious disease specialists almost use kind of like old school detective work to determine when infectious diseases are spreading. And the example I come back to is how they'll look at rates of fungal infection in animals in the Ohio River Valley to predict blaster mycosis infections in the population. So, I've always thought that's just really fascinating how they'll look for these little signals here and there that add up to more. Are we still actively doing that now with COVID or have things really relaxed from that angle? 

Krueger [00:13:19] Yeah, I think there's a couple different ways that places are looking at COVID. So, I think one of the most important metrics that we're looking at now are hospitalization rates and death, because, again, we know COVID is going to be spreading, but we really are very concerned about those more severe outcomes related to COVID. But there's also tracking still going on of just like total cases. It's important to kind of know what your local community spread is, because I think that gives people kind of the empowerment to make a decision how they feel about going to crowded indoor events or wearing masks if they know kind of what the local risk is for them. I think that can be really helpful to communities. And then, you know, since you brought up kind of the detective work and looking at different ways of tracking diseases, another interesting thing that scientists have done with COVID and other diseases like polio too, is actually look at the amount of disease in wastewater. So these diseases that are kind of shed through stool, you know, and end up in wastewater, you can actually kind of look at levels and that can be used to kind of predict peaks in certain locations. That was interesting, too, with the polio case that we saw out east, they were able to again, kind of detect how much of the polio virus that they were seeing and how much actually probably was circulating prior to someone getting sick from it. So, there's lots of different kind of good epidemiologic tools that scientists can use to try to keep an eye on these things and kind of get a sense when they may kind of be shifting towards a higher number of cases. 

Prickett [00:14:47] So I think the vaccines that we saw, at least for this pandemic, the science really seemed to move very rapidly and we weren't quite sure what to expect from them. Do you mind just filling in our listeners about how and why the vaccine for COVID came out so rapidly? What are some of the risks, side effects and success rates? And now that we know what we know, what are the recommendations moving forward? 

Krueger [00:15:11] I think I cried the day I got my first vaccine; I was so happy. 

Prickett [00:15:14] I know I did. I know. 

Russell [00:15:15] Just. Yep. Same. 

Krueger [00:15:17] It just felt like, yeah, it felt like the boost I needed. 

Russell [00:15:21] Had to go hide in my office. 

Krueger [00:15:24] The vaccine development was really an amazing feat. Normally it takes a lot longer to develop vaccines, so I'll just say, you know, a couple background points. So even though some new technology that MRNA vaccines specifically were employed in the development of COVID-19 vaccines, it's not necessarily new technology. That technology has been along for a long time and it's been studied for a while. It just had never gotten to a licensed vaccine previously. So, these pharmaceutical companies, along with the support of the U.S. government with Operation Warp Speed, were able to get a lot of funding, kind of shift all of their resources and all kind of simultaneously work on their different vaccine candidates. So just, in terms of time, first of all, just the amount of resources, financial and the amount of people that just dropped everything else they were doing to work on these vaccines was just completely unprecedented from what would have ever been discovered before in the creation of vaccines. The other thing that really helps with developing these vaccines quickly is because the prevalence of COVID was so high and there were so many people willing to volunteer in the clinical studies. And then just because cases were so prevalent, we were really able to get that data back so quickly and whether or not the vaccine was preventing disease. So, it's really kind of a multitude of factors that kind of went into the vaccine development and just really, you know, the urgency behind it. So, I will say that there were not steps that were skipped in vaccine development. That's a question I get a lot. But they did the phase one studies. They showed that the dose was safe. They showed what made the immune system respond. And then they went on to these trials where they enrolled tens of thousands of people. They had one arm getting the vaccine and another getting placebo. Both were blinded. And, again, all these manufacturers’ studies, and we were really able to see the differences between the vaccine group and the non-vaccine group. We know over time, as COVID has changed and we've developed new variants, that the vaccine efficacy against just total disease in general isn't going to be quite as good. But has still, you know, over the years really retained its ability to prevent the more severe disease, including hospitalization and death. And that's really the biggest goal at the end of this, is to, you know, keep people healthy and alive. It's a little bit of a game of catch up because as we get new variants and we kind of have to keep retesting the vaccine to try to predict how good the vaccine is going to be against this new variant. So a lot of times that is a little bit kind of delayed at the end of the day, how our vaccine is working against the most recent one to be circulating. So right now, what is recommended for everybody is to get the newest vaccine, which is bivalent. So, meaning it stimulates the body against kind of the original strain of COVID-19, the SARS-CoV-2, and then against omicron-specific strains of it. So that's, if you haven't gotten that yet, that's what's recommended for you. A lot of people out there still haven't gotten it yet, and I still do recommend that it's likely to provide some level of protection, although again, we're still trying to figure out exactly how much for these newer variants think going forward. There's a lot of discussion about what strategy is going to be best to use. We can't keep doing where we're vaccinating everybody every three months. It got to the point where I think people were just kind of like, this is too difficult to keep track of and do I really need a shot this frequently? My guess, if I had to say, would be that they'll probably try to go for more of like an updated annual vaccine kind of again, based on what's been circulating most recently, kind of similar to how we do influenza. I mean, that would probably be recommended across the board. But I think a lot of that is still kind of in discussion how best to handle that. 

Russell [00:19:15] I wondered if you could talk for a minute about the common viruses that have been such a problem, specifically flu and RSV, where we saw large numbers.

Krueger [00:19:26] We used to have like pretty clear influenza seasons, for example, and back to school, at fall, respiratory viral season with kids spreading viruses throughout schools and daycares and things like that. COVID 19 and everything we went through the last couple of years and social distancing and masking, etc., has kind of disrupted that to some degree. So, for a while we actually had like no flu season over the last couple of years, which was really interesting. But these viruses are never going to stay away forever. They're always going to find a way back in. And part of that could just be people are getting back a little bit more to a normal life. People are not masking as frequently as they once did. And I think people are gathering a little bit more. And that could definitely be related to why we just started to see these, kind of normal, typical fall and winter respiratory viruses start to circulate a little bit more. And then, yeah, we had a really bad year for RSV. And for those of you guys who aren’t super familiar with that out there, that's another respiratory virus we really worry about it in especially young children. It can be really, really severe and in immunocompromised or elderly adults. But good news on that front, there are multiple vaccines in development for RSV. I'm very excited for those to hopefully provide us some protection and another tool we can use to prevent these big outbreaks, especially where our most vulnerable members of society are being impacted. 

Prickett [00:20:56] What are the lessons that you as a infectious disease doctor, are going to take away that potentially our listeners could help with? 

Krueger [00:21:02] Great question. Yeah, I think I will forever carry hand sanitizer around in my pocket or purse. I just can't get enough hand sanitizer and I probably should have been doing that long before. I mean, we obviously do in the hospital when we in and out of patient rooms, but I hadn't done it like before I touch everything at the grocery store. So, I think hand sanitizer is a good one. I do. I think I think masks — especially when we're seeing really high rates of viral transmissions — masking is an absolutely great tool that we can use to protect ourselves, to protect other people when we may be transmitting and we don't even realize it. So, I think that is going to be an important tool that I'm going to use going forward as well, too. I'm not ready to take off my mask yet either, and people probably don't want me to because I have a daughter in daycare, so I'm usually the one spreading the germs. But yeah, I think on a personal level, those are some of the big ones. And then I think, you know, people really do have to think about what risks they personally want to take. So I think I've gotten better at being like, you know what, this family gathering is really, really important to me for my mental and social health. I need this, so I'm going to go to it. But there's other things where if there's a lot of stuff going around, maybe I could skip that one for right now. So, I think I've gotten a little bit better about making those decisions for myself. I think if people kind of have the information about what's out there circulating and what their own risk of getting severe diseases from these then they can make some of those decisions too. 

Russell [00:22:30] Well, thank you so much, Dr. Krueger. We've learned a ton, and I just want to say again, like how much we, as the critical care side of the street, pulmonary side of the street, love our infectious disease friends and colleagues. 

Krueger [00:22:46] Right back at you. 

Russell [00:22:54] Thanks for listening to Get Better

Gates [00:22:56] We hope you'll leave this podcast better than when you started. 

Prickett [00:23:00] For more information, visit