Local Wastewater Tests Show COVID Decline

A collaborative effort between the city of Corvallis and Oregon State University researchers has been progressing since July 2020 to monitor city-wide COVID-19 prevalence in a uniquely non-invasive way, and their results may play a large role in future re-openings of schools and business in Benton County.  

Dr. Tiffany Garcia and Public Utilities employees collect weekly samples of wastewater at multiple locations from the city’s sewer system, and samples are analyzed in Dr. Taal Levi’s lab on the OSU campus to identify the virus RNA. In contrast with most other COVID detection programs, like OSU’s TRACE project that relies on individuals seeking out tests for the virus, this method of sampling wastewater allows researchers to quantify theSARS-CoV-2 virus in different regions of the city.  

Referring to the numerous sampling locations the project is visiting throughout Corvallis for the last six to seven months, Garcia said, “I think the novel component of our Corvallis work is the spatial sampling methodology. We are trying to find spatial, as well as temporal, patterns in SARS-CoV-2 detection across the city.”  

Researchers are able to access and collect wastewater samples from points within the sewer systems that drain in North Corvallis, Southwest Corvallis, South Corvallis wastewater, and the Beca Street drainage. The project takes composite samples – meaning from more than one drain – at the Corvallis wastewater treatment plant and from Lower Corvallis, which drains all of South Corvallis, Southwest Corvallis, OSU, and downtown.  

“Most COVID wastewater studies are at the scale of the wastewater treatment plant, which is the municipality scale.We didn’t think that had enough resolution to pick up the nuances that were likely in a college town. And we were right,” Garcia said.  

While the project has detected viral RNA at all sampling locations, at some point during the duration of wastewater monitoring, Dr. Levi noted that within the past few weeks, viral RNA concentrations have clearly declined in Northern Corvallis, Southwest Corvallis, and South Corvallis, where few students live. The OSU/downtown basin, as well as the Beca neighborhood, remained hotspots within the city until two weeks ago.  

Benton County’s positive case reporting shows that the vast majority of COVID cases are occurring in people aged 18-29, and the wastewater project supports this. While Levi points out that more data needs to be collected over time before making policy changes, “if OSU’s recent increased testing in student residences leads to fewer infections, which it should, Benton County may soon respond with substantially fewer cases – below the suggested threshold for school reopening.” 

These hopeful signs come as COVID vaccination is becoming available to more groups of people, but occur at the same time as more strains of the virus are being detected across the country.  

The viral RNA Garcia and Levi collect from the wastewater samples also go towards monitoring for the prevalence of these different variants in collaboration with TRACE at the OSU Center for Genome Research and Biocomputing, which will help in combatting the pandemic. So while the declining trends shown through virus testing and the wastewater project are promising, it is important to remember that Benton County is still in the “extreme risk” category for COVID case rates.  

To learn more about the wastewater monitoring project, you can visit the projects website at http://people.oregonstate.edu/~levit/Software/CorvallisWastewater.html. Future results will be published in The Advocate’s weekly COVID column.   

By: Lauren Zatkos