The proof is in the poo: Sewage testing helps detect Austin COVID outbreaks early, researchers say

Inside a freezer at the Cockrell School of Engineering at the University of Texas at Austin is a collection of wastewater samples, drawn from the city's two major treatment plants over the last month.

They're stashed away while a team of researchers finalizes their procedure for analyzing them. The goal? To measure the concentration of COVID-19 in the city's domestic wastewater in the hopes of detecting outbreaks sooner.

"Everybody has to flush," Associate Professor Dr. Mary Jo Kirisits told Austonia. "Everybody is contributing their sample on a daily basis."

The practice of studying waste

UT researchers take samples to test for COVID-19. (Mary Jo Kirisits)

Kirisits, along with colleagues from the Cockrell School and the Texas Advanced Computing Lab, is working on the study, which was commissioned by Austin Water and is scheduled to run until June 2021.

The water utility is collecting samples three days a week, sometimes multiple times per day, for the researchers to analyze; they will share their results with Austin Public Health.

This type of wastewater analysis isn't new.

"Certainly looking and analyzing wastewater is something that has been done historically for other diseases where vehicles of transmission are being shed by feces," Kirisits said, adding that it continues to be used to detect polio in other countries.

Now research groups worldwide are applying the technique to monitor the spread of COVID-19.

Studies show that the viral RNA can appear in feces within three days of infection, which is much sooner than it takes symptoms to appear in some patients or for local hospital rates to reflect an uptick, according to an April report from the journal Nature.

Local health officials often lament this lag time between when an outbreak occurs and when it is reflected in test results or hospital admission rates.

But the hope is that this wastewater study can function as a kind of warning system, alerting researchers to any COVID-19 resurgences in the coming months. "If [cases] do start to uptick," Kirisits said, "we're going to be able to see that before the cases start arriving in the hospital."

How it helps contain a pandemic

Preparing the coolers.(Mary Jo Kirisitis)

The sooner researchers—and Austin Public Health officials—learn of an outbreak, the sooner they can act to contain it.

"If we find a hotspot in a part of Austin that hasn't been on the radar screen—because maybe people aren't getting tested in that area for whatever reason—we can say, 'Hey, maybe we need to increase the education about social distancing or mask wearing or hand washing in that area,'" Kirisits said. "Maybe we need to deploy more testing resources to that area."

Ideally, researchers will also be able to refine the sampling process by deploying autosamplers at different locations around Austin—such as inside a manhole—to help pinpoint where outbreaks may be occurring.

Relying on samples from the treatment plants, as is currently the case, means researchers can only know if an outbreak is occurring in the area served by one of the two treatment plants, each of which serves around half a million people.

"Really the point that we're at right now is to use this [COVID-19 concentration metric] to understand what's happening temporarily in our sewersheds here in Austin," Kirisits said. "It's going to be great when we get to the point that [it] is really coming down and it's below our detection limit."