OSU adding to Corvallis COVID-19 prevalence understanding via citywide wastewater analyses

CORVALLIS, Ore. – Oregon State University researchers say wastewater sampling for the novel coronavirus shows the virus is present in every region of Corvallis, with a moderate increase in virus levels over the past month following the low detection levels that took hold in mid-July.

“We are focused on keeping track of COVID-19 infections in the population through time and space, identifying hotspots of cases where public health monitoring should be directed,”  said Taal Levi, associate professor of fisheries and wildlife in the OSU College of Agricultural Sciences.

Wastewater analysis is being used as a COVID-19 monitoring tool in cities around the globe, the researchers say, and it can be paired with individual-based testing to corroborate results and expand monitoring by public health officials.

The findings by Levi and Tiffany Garcia, professor of fisheries and wildlife, align with what sewage researchers in OSU’s TRACE-COVID-19 public health project have discovered and are also in sync with results of TRACE’s door-to-door nasal swab sampling in Corvallis.

Levi and Garcia, with assistance from OSU environmental virologist Rebecca Vega Thurber, have been monitoring Corvallis’ sewer system since early May. People who are infected excrete novel coronavirus RNA in their feces, irrespective of whether they have symptoms.

“We saw a big shift in COVID-19 prevalence in mid-July,” Garcia said. “Early sampling sessions produced noticeably higher SARS-CoV-2 RNA concentrations relative to later in the summer.”

The late-summer decrease in concentrations indicates that COVID guidelines contributed to slowing the spread of COVID-19, she added. “This fall, we are detecting another increase in SARS-CoV-2 concentration, but Corvallis is still relatively safe compared to COVID-19 hotspots in other Oregon cities.”

The research team collects wastewater samples over a 24-hour period each week at seven Corvallis locations, organizing the analysis by district (north Corvallis, Southtown, southwest Corvallis and mid-Corvallis), locations of interest (Good Samaritan Regional Medical Center), and composite samples that consist of wastewater drainage from more than one area (lower Corvallis and the wastewater treatment plant). Lower Corvallis is a composite of eight drainage basins in the central and south parts of town, and the wastewater plant sample is a composite of all 19 of Corvallis’ basins.

“Right now, all basins in Corvallis that have been tested have had novel coronavirus detections at some point,” said Tom Hubbard, utilities division manager for the City of Corvallis Public Works Department. “There’s nowhere in Corvallis where you shouldn’t be vigilant.

“The spike in July when we were waiting for COVID-19 restrictions to take hold was the biggest and worst – worse than when students returned to OSU,” he added. “And even though levels are relatively low compared to other areas in Oregon and the United States, we need to stay on guard.”