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An Expert's Take On The Numbers

You may listen to this conversation in its entirety here:

Lori Walsh: And we're joined now by epidemiologist, Elizabeth Racz, who is with the South Dakota School of Mines and Technology. And some of the things, Professor Rocks, that the governor was saying was this notion of assessing surge capacity, which is ongoing. And that basically, for people who are just tuning in, it means looking at the hospital beds, looking at the ventilators in the intensive care beds that you have now, using models to predict how many you might need if a certain percentage of your population gets sick, and matching this up and being ready to respond. So Elizabeth, welcome back to In the Moment. Thanks for being here.

Elizabeth Racz: Sure. Thank you for having me.

Lori Walsh: So one of the things that people are really wanting to know is, really about data and how we're tracking this. And the last time you were on you said it's hard to when you don't... It's like being a detective and not having all the clues. We're following these numbers so closely. We heard her say there's two new cases, we heard her say eight people are recovered. But there's lots of information that we don't know. Help us understand what data should we pay attention to and at what point do we stop paying attention to data because it's incomplete?

Elizabeth Racz: Okay, well those are very good questions, and I can see very easily why people would be interested. And we want to make sure we're getting the correct info right away. So the first thing we need to remember is that the data that we're getting in is data that is being publicly reported of confirmed cases. Now that is a small subset of what is actually going on out there. Now some of the people we know are asymptomatic and they are still able to spread this illness. So it's very important that we treat people as if they have the coronavirus infection until we get more data. So it goes back to Dr. [Fauchi's 00:02:00] comments of, if you don't know if you have a case, you need to still act like there could be one.

All right, so the numbers we need to pay attention to. We want to pay attention to, of course, just the number of new cases that are coming in. We want to be sure we're looking at whether or not they're travel related or community spread. Those are two different things in the sense of how you might be concerned and how you might respond. So what you want to do is tear the numbers apart in the sense of how is the information surrounding this case going to be responded to? What are the actions that need to be implemented?

So for travel we want to, of course, get the patient history and track back where they had come from, and isolate the person. With community spread, this sends a red flag up saying we have this going from person to person in our community, and those numbers, we still need to track who they came into contact with and talk to those people and get more information about them. But the difference is, is that's when you have to start doing things like self quarantine and asking people who aren't specifically infected with the virus to take action to protect the larger community. And so that's why we have this data reported on the cases as travel versus community spread and why that's so different.

Lori Walsh: Yeah, I'm going to jump in here, because you really only have a minute left. And so we're going to have to have you back on, but I have one question I wanted to get to today.

Elizabeth Racz: Absolutely.

Lori Walsh: And that's this idea that there are so many negative cases that we don't know about because the local labs aren't reporting the negative, they're only reporting the positive. And some people are arguing that the situation is not as bad as we think it is because we're not really counting the negative cases. Does it matter? Or do we just look at the positive cases and say, if you've got spread, you've got spread. Help us sort that through in 30 seconds or less and we'll have you back on later.

Elizabeth Racz: Okay. It does matter, and this is a big issue right now because we are balancing back and forth between protecting the health but also worrying about people's livelihoods and keeping them afloat. So what I would say is, it does matter that people who are asymptomatic can spread and that we do need to track those cases. We don't have enough testing capacity right now to do that. Once we come out with antibody testing, perhaps we can get a bigger picture there, but for right now, because we can only work with the data that we have, good data in, good data out. Well, we don't have the greatest data in right now, but it's getting better. We are trying to get through this backlog. We do need to realize that this is worse, because the people who are getting ill, there is a high death rate. Even if it's the lowest estimate that we're coming up with, it's still 10 times higher than influenza and how do we keep people better is on those ventilators.

Lori Walsh: All right, we're going to have to leave it there. We'll have more.

Day Two Interview:

Lori Walsh: Yesterday we talked just for a few minutes about getting more data, and the data that we know, and what we don't know. And we can get back to that a little bit more. And I especially want to ask you about Dr. Anthony Fauci's press conference comment where he said, we really need to shine the light on these places that haven't had a lot of testing, how that changes things. But I'm hoping we can start today with this number that governor Christie Nome gave out at a press conference, I think it was just yesterday, where she said 30% of South Dakotans are going to get sick and 80% of those will have mild symptoms from coronavirus, but that leaves 20% of people who have more than mild of problems. So let's talk about that 30% number because by my calculations, we're talking 264,000, almost 265,000 people getting infected, and 52,000, almost 53,000 people getting seriously or moderately or seriously ill. Help me do the math right. Help me understand this math. When she says 30% of us are going to possibly be infected, unpack that please.

Elizabeth: Okay, well when you hear 30% you immediately go, I'm going to run the numbers. Just like you did.

Lori Walsh: Right? Just like I did.

Elizabeth: Right, right. So as far as where that 30% came from, the model she's referring to, I was unable to find the source for that. And so was also our university relations department. So I would just say that 30% came from her office. I don't know what she has access to.

The information I have access to, according to a Harvard study, says that the percentage can be between 40 and 70%. Now different areas are going to experience different percentages, because different areas have various co-factors that will affect that percentage. But yes, when you say 30% or 40% or a given percentage, you're talking about a subset of the population.

So we have 880 some thousand people living in South Dakota. Now when we talk about the 247,000 people who could have the COVID-19, many of those will be asymptomatic. Now that's great news, but it's also bad news because this virus has what people are terming stealth spread.

What it really means is that during the incubation period, which is the time between when a person is infected and when they first start showing symptoms, during that time, whether you're going to be asymptomatic or not, you can spread the virus. So that's a seven to 14 day window, five to 14 day window in which people are spreading the virus and have no idea that they're doing it. They're coughing, they're walking away, someone else walks through that cloud that they coughed out within three hours. And there's still potential for that next person to become infected with the virus. So this is something that really says, we need full buy-in from everyone. Asymptomatic or not.

Now 20% of those people who could get infected, not to get too lost in the numbers, but of that 240,000 some people who could potentially be infected, 20% of them are thought to develop severe conditions, and that's designated not just by age but also by underlying condition. So that's something to keep in mind. Anyone is susceptible.

Lori Walsh: Okay. And then that's 53,000 people, almost. 52,900 people, in South Dakota.

Elizabeth: Which is a huge number, especially when you start thinking about two things. You start thinking about our healthcare capacity. We are a rural area. We have our healthcare system's capacity set. It's fairly limited compared to other places, in the sense of the number of ICU beds that we have compared to New York. We also have fewer people, but it might mean that we have to come up with novel ways, or think outside the box a little bit. Are we moving? Are we going to take the risk of moving patients from one county to another because there's an ICU bed there? When you start talking about 53,000 people, you start thinking about how we may not have ventilators for people, which if they have severe symptoms is vital for them to make it.

And also a major concern right now, and something I would really like to bring up that I think is really important when we're talking about all these curves and spikes and flattening the curve. If you imagine that diagram we've all seen, or that graph we've all seen with the big curve of what would happen if we don't have any interventions, and the flatter curve with the little dotted line there, the flatter curve is where we have intervention and the dotted line is our health care system capacity. If we have people who are unprotected in our healthcare system, people on the front lines without the proper PPE, the personal protective equipment, that is going to drop that dotted line. If we drop that line, that curve has to get even flatter to protect the vulnerable population.

We've talked about how important it is to protect people. We don't want them getting sick. We don't want to overload our healthcare system, which is all true. But the larger impact of that on the overall curve is that that curve may need to be almost flattened to a point that we can't really get to, and that's when we get into hard situations.

Lori Walsh: So in simple language, if half your respiratory therapists are sick and can't come to work, at some point, it doesn't matter how much equipment you have, how much PPE you have, you have to protect those frontline people because if they're down in the bed, that makes the whole situation exponentially worse.

Elizabeth: Right. If our nurses and doctors and EMT, firefighters get infected, they're not there. They're either potentially self quarantining, or maybe they're isolated for this period of time, especially if they have underlying conditions themselves. And that takes them not only out of the healthcare system, reducing the capacity, but it puts them into the category of patient, and adds even more stress to the healthcare system. So it's kind of a double whammy.

Lori Walsh: Let's talk a little bit about the duration, because Dan Heineman was telling us, he's from Sanford Health, yes, if 52,000 people need services at once, the system is overwhelmed. We need to spread that out as far as, we need to limit those numbers but also spread it out. Governor Noem said our cases should peak in late April, early May. Talk to us a little bit about that peak, that three week period that... Help us understand what that peak means.

Elizabeth: Okay. So whenever we have a new virus like this spilling over into a naive human population, everyone is susceptible. And we have questions. We want to know, how do I protect myself, what's going on? And we want to understand how this virus spreads. And one way that we can determine how a virus is spreading is by reporting the cases every day, and looking at the patterns over time. And right now with the lag in testing, we don't have a full picture, and we also have a backlog of cases right now. So we're going to see spikes, but they're not going to be true spikes that happened at this day. We have to remember that they happened in the past. We're just seeing them today.

Now this curve that we're seeing is based on a rate. And what it is is once you find out the rate, the speed of how this virus is transmitted, how it's spreading across population, you can graph that out. And one way we do that is by looking at the time that people are infectious. This infectious period, how many people they come into contact over a unit of time, and also what the mode of transmission is. So the faster this virus spreads and the longer the incubation period of a virus, the higher this contagious organism can spread. And we measure that in a term called RNOT. And that term basically is looking at, if you have a primary case, how many people on average will that primary case infect and have them become secondary cases?

Now when you have this information over time plotted, you need to also take into consideration the generation time of the virus. So this is sometimes called the serial interval. And that's the interval in which a case that becomes infectious, that primary case, and that that average secondary case then becomes infectious. It's just the defining time on that generation period for the virus.

So when you have the RNOT and this generation time, so when you understand the rate at which the virus is spreading and you understand the generation period, you can start making inferences about whether or not the epidemic is dying out or spreading or maintaining the same. And what we're seeing with the COVID virus is that it basically, over generation period, so with the COVID virus, it's about a week. We can see that a single person who's infected is spreading out to about two, 2.5 people, on average, 2.2 people per generation time. So that gives us a rate. And when you have a rate over a period of time and you can start seeing whether or not you have this spread continuing, and when they're graphing this out and they're saying, Oh, there's a peak coming, that's because based on the rate we're seeing over the period of time, these weeks, that's where we expect the number of cases to be.

So per week we go up a certain amount and over a certain number of weeks we get to a certain number of cases. And beyond that, maybe they're projecting that the cases will go down. There are other factors that go in, but it's all basically very sensitive to whether or not there's exposure, and the probability of that next person becoming infected. It's very, very sensitive to that.

And that's an opportunity. That's an opportunity for us to change behavior. We don't have a vaccine yet to change that, but we do have the opportunity to change behavior and that's where the social distancing, or now the physical distancing as the WHO is calling it, is coming in because we want to stay mentally close but physically distant. So that peak is where they're estimating we will be based on the math.

And what's key about knowing where we're going to be on that peak is because we need to match up that estimated number of cases that are coming in the future with our healthcare capacity. How many ICU beds do we have? How many ventilators do we have? Do we even have the personnel to deal with this? Again, as we mentioned before, it doesn't matter how many ventilators you have, if you have no one trained to run them.

Lori Walsh: Right. So people are listening as we bring our healthcare leaders on and have conversations about what they're getting ready for. And people are listening for numbers that they're not hearing. They're saying, what exactly is the plan? You say you're working on surge capacity. We talked to Monument Health last week and they said, they could go up to 100 beds, after that would be a true emergency.

Well, according to this coronavirus study about hospital preparedness across the nation from Harvard, you could have 14,600 coronavirus patients in Rapid City over a period of 12 months. That's 490 beds. So you look at how the math breaks out and getting up to 100% or doubling the number of beds is just not even close to good enough.

Talk a little bit about how do we evaluate what the hospitals are telling us from a surge capacity standpoint, and match it up with what we know from the math that people like the researchers at Harvard are doing.

Elizabeth: Well, I think what it shows us is that we have a gap. We have a gap between what's happening and what we can handle. For a long time, our public health services have not been funded and grown to the point where we could handle a pandemic. We aren't as prepared as we would like to be. You may have heard about the news in New York with people not having enough beds yet. They're turning the convention center into a place where they can treat people. So we may have to think outside the box here, because what it is the numbers are telling us, is that we are going to, with the information we have, we are going to pass our health care system's capacity.

And now, I know we talked a little bit about concerns about, well we don't have all the information on all the cases because there's a lot of people out there who aren't tested. And there is something to that. We don't have all the data, but based on the data that we do have, and what we are seeing, this is what we have to do. We have to prepare, we have to work together. I know that there are chat rooms different physicians around the country are getting into to trade equipment and get advice from one another, especially as some of the symptoms and pathologies are becoming either more severe or presenting themselves in other demographics.

Lori Walsh: Right. All right, well this is an ongoing conversation and we hope you'll come back as it unfolds, and help us continue to understand this. The bottom line right now is just because the state has a list of 41 positives as of today, that number is going to go up to huge amounts in the thousands, and the efforts that you're making now in your communities, in your cities, in your farms, and inside your houses really does have an impact. That's the bottom line here, take those steps. Yeah.

Elizabeth: It absolutely does. It's helping to stop that exponential growth. Because with exponential growth, you don't see how big the impact is going to be until you really progress along over time. But for a long time it'll seem like, Oh, it's not growing very much. It's not, and then boom, it just explodes because if everyone who's sick passes it on to around two people every generation period for the virus, and then those people pass it on, and those people pass it on, very quickly you get into a not good situation.

Lori Walsh: All right. We'll bring you back as soon as we can. Elizabeth Racz. Thanks so much.

Elizabeth: Thank you very much.

You can access all of SDPB's COVID_19 coverage at www.sdpb.org/covid

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