Study: Sewer samples signal pending rise or fall in COVID-19

RENO — Researchers at the University of Nevada, Reno say they have developed a model that helps predict if confirmed COVID-19 cases in a local community will significantly rise or fall in the week ahead.
Scientists say data sampled from sewers and wastewater treatment plants in the Reno-Sparks area last year showed a correlation to the number of positive tests for coronavirus that would follow in about seven days.
"It clearly reflects the extent of the disease as it was determined by human testing, so it is a good leading indicator of what's happening in the community," said Krishna Pagilla, a UNR professor of environmental engineering who led the study.
The team monitored sewers and wastewater facilities from last April to December to keep track of concentrations of the virus that causes COVID-19.
They said in the study released in late March that an increased presence in concentrations preceded a formal uptick in confirmed cases about a week later because of the lag in those infected seeking tests.
"It's predictive because people don't get tested until they have symptoms, but our marker concentrations are real time — as soon as the virus is discharged into the wastewater," Pagilla said in a statement released by the university.
The university partnered with the city of Sparks to sample wastewater at 12 sewers in the area and three water reclamation facilities a few times a week.
The results are being reviewed by many other cities to determine COVID-19 prevalence in the absence of extensive clinical testing of humans, university officials said.
"Using the monitoring samples, we can't separate out just the vaccine effect, but overall if the pandemic is decreasing and the number of cases is going down — that we are able to clearly see through wastewater-based monitoring," Pagilla said.
Sparks Assistant City Manager John Martini said Washoe County, Reno and Sparks used federal coronavirus relief funding to help finance the study.
"We can see the amount of genetic material in wastewater rise as we hit the spike in October, November and into January. It tracked very well with testing results on people in our communities," Martini said.
Michael Drinkwater, manager of the Truckee Meadows Water Reclamation Facility, said the majority of the wastewater in the community comes through that facility.
"We looked at the entire treatment process, which included the influent and effluent," he said. "The virus was clearly detected when coming into the plant, but not detected in the outgoing, so we can say definitively that the virus does not survive the wastewater plant and the water going back to the Truckee River is free of the virus."


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