What does Utah’s sewage say now about how prevalent COVID is in our communities?

Here’s the scoop on the poop: Virus is trending down in some major areas.

Rick Egan | The Salt Lake Tribune A wastewater treatment plant, shown in 2017, in Salt Lake City. Recent samples from such plants show COVID-19 is decreasing in the biggest, most populated communities of Salt Lake County.

There’s one surefire way to know if the coronavirus is truly waning in our community: #PoopWatch.

That’s the informal name, coined by our Salt Lake Tribune columnist Robert Gehrke, for Utah’s coronavirus sewage monitoring system. It’s a gross method of data collection, to be sure, but it’s also an effective one, measuring populationwide trends like no other system can.

That’s especially true in the omicron winter of 2021-22. Public health officials still don’t want people to be tested for COVID-19 if they have symptoms, instead just asking people to stay home. It’s a controversial policy because, obviously, that reduces the number of positive tests that get added to our daily case counts, and makes it harder to track what’s happening.

Even without that edict, testing can have inequalities and inadequacies: for example, the rich might have more time or flexibility to wait in testing lines than the poor. Heck, even something as simple as whether a local Walgreens was able to keep at-home COVID-19 tests in stock would impact the official Utah Department of Health’s daily numbers.

Hospitalization data is better but can be significantly affected by, for example, outbreaks in various age groups. It’s also a lagging indicator. It takes time for people to go from infected to contagious to symptomatic to having severe enough disease to end up in a hospital.

Meanwhile, everyone poops. And when people have COVID-19, live and dead copies of the virus show up in that waste — all of which gets pooled at a sewage treatment plant.

Therefore, when scientists at the Utah Department of Environmental Quality take samples from the mixed sewage entering 42 of Utah’s treatment plants, there’s no skew, no bias in the data. It is truly representative of the population as a whole. (Well, almost everyone. About 20% of Utahns live in an area that doesn’t use one of the 42 treatment plants.)

They then send those samples to the Utah Public Health Laboratory, where they count how many copies of the coronavirus gene can be found in the sample. The only quirk is that the timing of data collection and upload is a bit unpredictable — sometimes, only a couple of days pass between data points; other times, it can be a week.

So what does #PoopWatch tell us?

First, that the rate of the coronavirus truly is declining from peak levels reached two or three weeks ago. Take the measurements from the Salt Lake City Water Reclamation Facility, which serves 209,000 residents.

Two weeks ago, there were 4,476 million gene copies per person per day in the sample. (Don’t worry too much about the units here; just treat the numbers you see as an index to compare to previous days or other locations.) Now, we’re at a sixth of that amount, as of the last measurement taken last week.

(Christopher Cherrington | The Salt Lake Tribune)

That’s obviously a terrific sign! A downward trend is to be celebrated. We should note, however, that levels remain higher than they were for most of the rest of the pandemic. Yes, by early January standards, we’re doing well. By 2020 standards, there’s still a heck of a lot of virus out there.

For each of the 42 treatment facilities, there’s a similar graph. The state color codes the plants by the recent trend displayed in the data: Are cases increasing, decreasing, or staying about the same? (Click here for a full-screen version of the information below.)

The good news is that we are seeing decreasing trends in the biggest, most populated communities of Salt Lake County. In the samples taken at the Salt Lake City, Central Valley and South Valley water reclamation facilities, it has been downhill in recent measurements. That’s great.

The news is slightly more mixed in some of the surrounding county treatment plants. Weber, Davis and Utah counties, as well as those in the southern end of Salt Lake County, are categorized as places with “no trend” in their recent data. All are off of the highs of the omicron wave, but the end of the wave isn’t approaching as quickly as it is in more populated areas.

For individuals, this can inform good decisions on how to approach the pandemic. How safe is it out there, and what are the relative risks of going out in different areas? For the immunocompromised or otherwise high-risk folks, especially, good data can be critical.

But #PoopWatch data can also be useful for all sorts of other community decision-makers. Where are schools most likely to need substitute teachers? Well, it’s where sickness is spreading most. Where might the next wave of nurses be needed? Well, it’s likely going to be where you have the intersection of large amounts of virus and large numbers of unvaccinated people. Where are more DoorDash drivers going to be needed to deliver chicken noodle soup to the quarantined sick? Et cetera.

The data shouldn’t be taken alone, and, in particular, hospitalization and death data remains key. Even case counts are still somewhat useful. (For example, case counts are searchable by small census area in Utah’s dashboard, or even by ZIP code in Salt Lake County’s dashboard.) There’s not one all-in-one metric with which to best track the pandemic.

But if I’m looking for a metric that’s going to be unaffected by changing testing protocols or availability, #PoopWatch is my go-to source for the least-skewed data.

Just don’t make me think about how it’s collected.

Andy Larsen is a data columnist for The Salt Lake Tribune. You can reach him at alarsen@sltrib.com.