Austin wastewater helps UT researchers track COVID-19 transmission

Leila Saidane, News Reporter

UT epidemiologists are using fecal matter from Austin’s wastewater plants to track the transmission of COVID-19 in the area.

Led by Mary Jo Kirisits, an architecture and engineering professor, the research team analyses composite samples from the city’s treatment plants to monitor the spread of COVID-19 and compare the levels of the disease found in the wastewater with city reports. 

“I think it’s useful for looking at trends over time,” Kirisits said. “We look at case counts over time: Is the concentration rising? Is it falling?”

Researchers collect composite samples of wastewater at city treatment plants over a 24-hour period, according to Kirisits. The samples are then brought to the lab where researchers concentrate the sample’s SARS-CoV-2 and extract its mRNA. A transcription method is then used to count the number of copies of a particular gene in the SARS-CoV-2 genome, Kirisits said. This process can identify different COVID-19 variations.

Alisa Lu, a math and Plan II senior, said she used the data to find correlations between COVID-19 case count data from Austin Public Health and the COVID-19 mRNA levels within the wastewater. 

“Prior to coming into the project, I had no idea that wastewater epidemiology was a tool that we can utilize to monitor disease,” Lu said.

Whether an individual is symptomatic or not, COVID-19 is still shed through fecal material that is picked up in wastewater, Lu said.

“One of the big findings was (that) the case count data that’s reported by Austin Public Health sort of underestimates how many cases there are,” Lu said. “If you’re asymptomatic, the probability of you going to get a COVID test is not very high. … It’s underestimating how many cases there actually are, which was the motivation behind the project in the first place.”

The project attempted to determine if there was a lag or lead in the time between the levels of COVID-19 mRNA in the wastewater and the city case reports, Lu said.

The project also observed spatial differences with COVID-19 levels in Austin, looking at trends within zip codes to study the transmissibility of the disease. The study found that COVID-19 levels were high in East Austin and low in West Austin.

“The East/West trend also reflects several underlying socio-demographic patterns. Specifically, Eastern Austin’s zip codes have … more vulnerable and lower income levels compared to zip codes in West Austin,” Lu said. “If (the zip code is) more socially vulnerable, the people who live in those communities are more at risk of succumbing to COVID.”

The researchers began collecting samples from the Omicron surge at the end of December and will analyze them this semester, Kirisits said. 

Wastewater epidemiology has been used nationally to track the transmission of COVID-19. On Jan. 21, the Centers for Disease Control and Prevention published a study finding early evidence of the Omicron in community wastewater, suggesting that the variant was spread before the first reported case on Dec. 1, 2021. 

“The next thing that we’re going to be focused on with this is prominently looking for … the dominant variants,” Kirisits said. “Do we see new variants arising over time? Presumably they’ll be dominated by Omicron as we proceed in other geographical regions, but the data will figure out if it’s true.”