There’s so much COVID-19 data being reported. What does it all mean? KUNR’s Lucia Starbuck talks to Brian Labus, an epidemiologist with Nevada’s COVID-19 medical advisory team, to break down what the numbers can tell us.
Lucia Starbuck: Can you tell me a little bit about yourself and what your role has been during the COVID-19 pandemic?
Brian Labus: I’m an infectious disease epidemiologist. I’m a faculty member at the University of Nevada, Las Vegas, and so I’ve been involved in a lot of the response on campus. I’m also a member of the governor’s medical advisory team. We’ve been providing advice to him since we were formed in March about all sorts of different aspects of this, giving him an understanding of some of the science behind it, and allowing him to make better decisions, hopefully, with the ways we’re talking about looking at data or looking at particular issues.
Starbuck: I’m picturing you, like many of us, are looking at these COVID-19 numbers every day. What data sets do you think are most important to look at?
Labus: The numbers that I look at are the percent positivity rate. That takes into account the number of people who have tested positive and also considers the number of people who were tested. So, if we test twice as many people, and you get twice as many positives, it doesn’t mean there’s really a change, it just means you’re testing a lot more people. That’s why that rate is important.
The other thing that I look at is the hospitalization data, because the hospital data should pretty accurately reflect what’s going on in our community with transmission. There’s always a little delay in it, but people don’t just get hospitalized for no reason. You can get tested if you’re asymptomatic, you can get tested because you're sick, you can get tested just because you’re curious, there’s a lot of reasons, and so those numbers fluctuate, but you don’t get admitted to a hospital unless you’re very sick with COVID.
Starbuck: Can you talk about this balance between the numbers that you're looking at versus the numbers that people want to see every day?
Labus: There’s some data that has more value than others. People are really interested in the [number of] deaths. Those are important numbers to look at the severity overall in our community, but looking at those things day-to-day really doesn’t tell us what’s going on with the pandemic, because it takes time between when a person is exposed, and when they get sick, and when they go to the hospital and ultimately die. So, that data trails reality by a month or so. If we see a lot of deaths today, it means there was a lot of transmission in the middle of November. It doesn’t tell us exactly what’s going on right now.
Starbuck: I think that our listeners are looking at the number of new cases reported every day, and I know that's not the best number to rely on, but why not?
Labus: In order to be considered a new case, you have to test positive, and the way we test people changes over time. One thing we saw in Northern Nevada was the testing system was starting to get overwhelmed, so they said they were only going to test people who had symptoms. Well, that changes the way we’re looking at our population. If the number of cases goes up then, it’s not really reflecting the same thing that it did maybe a week before. So, that’s why if you just look at the straight numbers of people that are testing positive, the number of cases, it kind of gives you a little bit of a misleading idea of what’s going on.
The other issue we have with that is things change day by day. If you look at the data, the people that got tested on Thanksgiving dropped way down, because it was the holiday, and then it spiked the next day to make up for it. It doesn’t mean that cases went down, it means that the testing system changed from one day, to the next, and to the next. So, that’s why I don’t look at those numbers the same way I do that positivity rate.
Starbuck: It can even be as much as, more people get tested in the beginning of the week versus the end of the week, right?
Labus: Right, and more people seek care earlier in the week. This is something we see in a lot of diseases. We see it in flu season like that. Mondays are always really busy in the emergency room, and then the numbers kind of drop down over the course of the week. So, every Monday there’s a little bit of a spike, followed by a little bit of a decline, and then a spike. That’s why we use a seven-day moving average to take care of those day-over-day differences. It’s just human behavior, where if people are feeling a little bit sick, they might wait until Monday if they need a note to get out of work or something like that. So, we know we have those changes and that’s why we kind of smooth the data over a seven-day period to take out those little fluctuations that really don’t mean anything.
Brian Labus is an epidemiologist with Nevada’s COVID-19 medical advisory team.