Swabbing the community one flush at a time: Nevada researchers test wastewater to track coronavirus

I-Team Special Reports

Scientists use sewer samples to track COVID-19, other diseases

LAS VEGAS (KLAS) — What you flush is helping researchers track COVID-19 before cases spike and as new mutations of the virus appear.

Scientists from the Southern Nevada Water Authority take samples from wastewater to see how much coronavirus is in our sewer system. These results help public health leaders find spikes and clusters before they can be identified through traditional testing methods.

“I don’t think it’s something that somebody thinks about when they flush the toilet, but there’s definitely value to what’s going down the toilet,” Daniel Gerrity, the water authority’s principal research scientist, said.

Every Monday, Gerrity drives out to the Flamingo Resource Center, a sprawling facility handling 100 million gallons of sewage a day, to fill two gallon-sized jugs.

The wastewater he collects is a snapshot in time. The untreated wastewater, which resembles a murky liquid, contains bacteria and viruses our bodies shed. By sampling the water, researchers can see what substances our bodies are excreting.

“As cases go up, our wastewater concentrations go up,” Gerrity said. “Then as cases go down, our wastewater concentrations go down.”

Coronavirus primarily affects our lungs, but the virus also causes secondary infections of the gastrointestinal tract, according to Gerrity. As the virus duplicates and is shed out of our bodies, some identifiable factors show up in our waste.

“It basically gives us an opportunity to swab the entire community all at one time,” he said.

Data provided to the I-Team shows spikes in COVID-19 found in wastewater show up about a week before increases in new cases. The concentration of COVID-19 in wastewater increased at least tenfold in December, Gerrity said.

“That’s a pretty big jump from what we’ve seen since we started,” he said.

The amount of genome copies per liter was below 10,000 at the start of the pandemic. During the first week of January, the amount rose to nearly 1 million copies per liter.

A chart from the Southern Nevada Water Authority shows new COVID-19 cases plotted with the amount of COVID-19 detected in wastewater. Notice the difference of scales. (KLAS/SNWA)

Researchers are also finding fewer cases of other contagious diseases, suggesting prevention mechanisms are pulling double duty.

“The normal illnesses and diseases that people get, we don’t see that as much, because people are being more cautious to try to prevent themselves from getting COVID-19,” Gerrity said.

As the pandemic continues, Gerrity will keep his Monday routine. As Mother Nature calls, scientists will continue studying what we are leaving behind.

“Wastewater is often viewed as something disgusting that people just want to go away,” Gerrity said. “But actually, from a scientific perspective, it gives us a window into the community.”

Researchers at the University of Nevada, Las Vegas, are also studying the samples, focusing on the makeup of the virus and its mutations. The research will become even more important as more of the community gets vaccinated to see how test effectiveness it is.

Copyright 2021 Nexstar Media Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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