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Behind The Numbers: How To Read Utah's COVID-19 Statistics

Illustration of people waiting in line wearing medical masks and two medical workers standing nearby
gmast3r via iStock
Dr. Andrew Pavia says positive COVID-19 tests per day is the best indicator of how many new infections are occurring, but it isn’t perfect because it can depend on the number of tests that are done.";

For months, the Utah Department of Health has released daily statistics on COVID-19. To find out which numbers are most important to understand the outbreak, KUER’s Caroline Ballard spoke with Dr. Andrew Pavia, who has worked in pandemic preparedness and serves on a number of COVID-19 task forces for Utah’s hospitals.

This interview has been edited for length and clarity.

Caroline Ballard: Every day the Utah Department of Health releases an update on coronavirus in the state. That includes new cases, recovered cases, new deaths and the percentage of tests that come back positive. What do all these numbers tell us?

Andrew Pavia: Positive tests per day is our best indicator of the number of new infections that are occurring. But it's not perfect. The number of positives can depend on the number of tests that are done, so one of the ways you can correct for that is to look at the percent of all the tests that are done that are positive, and that gives you some idea of the intensity of disease that's out there. 

We have seen for the last week a big increase in the number of positives and the percentage of tests that come back positive. That includes not just people who have symptoms, but also people who were tested for other reasons, like before they're having surgery or because they were a contact of a contact. So when the overall state numbers showed that 10% of those tested are positive, it underestimates it. When we actually look at those who had symptoms who were tested within the Intermountain [Healthcare] system, it's been closer to 15 to 17% in the last few days. And that's a scary number for us.

CB: If you had to pick one or two, what pieces of information should the average person be paying the most attention to?

AP: The most important number is the one that you can't really see directly from the report, and that's the average number of positives in the previous week. That's more important than the number today because it smooths out the effects of “was it a weekend day two days ago with less testing” or “did a mobile testing site go up to do an investigation?” 

The least meaningful number that I wish we would stop reporting is the number of recovered people. That’s simply taking the number of people who were tested more than three weeks ago who haven't died and artificially labeling them recovered. It really doesn't mean much.

CB: Leaders have pointed to hospitalization rates and death rates to judge the severity of the disease in the state, and they've used those relatively low rates to justify reopening the economy. Are those indicators being used correctly and are they sufficient?

AP: In my opinion, they're not sufficient and they are not the most important indicators that we should be using. Death rate is heavily dependent on the health of the population and the age of the population. We've got one of the youngest populations in the entire country and one of the healthiest populations. That's something to be proud of, but that means that our death rate is going to look better than our neighbors because of that. 

Hospitalization rates are important because if we overwhelm the hospitals, we're in real trouble. But there's a problem with looking at hospitalization rates, and that problem is that it takes about 14 to 17 days between when a person is infected and when they're hospitalized. So if you're looking at hospitalization rates, you're looking in the rearview mirror. I think that's a grave mistake that our leaders are using, but it tends to look better, and I think there's a real tendency of politicians to look for the good news.

CB: On Monday, KUER reported a week long positivity rate of around 10%. What do you make of last week's spike in cases?

There’s a number of things going on that would contribute. I think one of them is going to yellow [the low-risk phase]. Not that we opened businesses by going to yellow, but that many people got the message that this was behind us and they could relax. We've all seen people who've stopped wearing masks — who are congregating in groups again, and that sort of thing is contributing to increased spread. Another big contributor was probably Memorial Day weekend. It's traditionally a time we all get together. On top of that we're now seeing one fairly large outbreak that is from the meat packing plant in Hyrum. But we're also seeing other small outbreaks, such as the one at the VA nursing home. So all of these things have combined to really dramatically worsen the picture of disease that we're seeing.

CB: As a state, where do you think we're headed?

AP: I don't know. I think that Utahns are resilient. They tend to be more willing to do things for each other than many Americans are. So I think we have the ability to really ramp back up the individual things that we can do and the things businesses can do to improve transmission without shutting down again. But I'm not yet seeing that message being clearly articulated by our political leaders. I think the desire is to separate the idea of health from the idea of the economy, and you can't separate those. If we want the economy to work, we've got to stay healthy. If we continue to have 300 cases a day it's going to have tremendous economic impacts — to say nothing of the human tragedy. We have to be smarter. We have to be safer.

Caroline Ballard hosts All Things Considered at KUER. Follow her on Twitter @cballardnews

Caroline is the Assistant News Director
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