Real-time wastewater testing can identify virus spikes early

Testing of wastewater for the presence of the coronavirus is able to identify spikes in infections before testing of individual humans can, a study in Northern Nevada found.

Sampling of Truckee Meadows wastewater found a clear spike of concentrations of the virus about seven days before the spike appeared in the results of testing performed on people, the University of Nevada, Reno, announced Tuesday.

“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,” Krishna Pagilla, an environmental engineering professor and leader of the study, said in a statement.

Wastewater testing can also detect traces of the virus from infected people who may be asymptomatic.

Michael Drinkwater, manager of the Truckee Meadows Water Reclamation Facility, said in a statement that the virus was found in sewage going into the treatment facility, but officials detected no virus in treated water coming from the plant. That means the water going back into the Truckee River does not contain traces of the virus.

The wastewater surveillance was funded with CARES Act money from Washoe County and the cities of Sparks and Reno, according to the news release announcing the findings.

Mark Pandori, director of the Nevada State Public Health Laboratory in Reno, has said he thinks wastewater testing could be a “surrogate” for testing of humans, but it remains unclear how many people in a community need to be infected to register a positive test result from the sewage.

“We believe the importance of wastewater testing will increase as people tend to stop seeking testing, because it might be our only canary in a coal mine that we’ll be able to use to know if this thing creeps back into our communities after we’ve beaten it down,” Pandori said this month.

Pandori said the infrastructure for sewage testing exists, but officials need to apply for money from the Centers for Disease Control and Prevention to expand wastwater testing efforts.

Pagilla said wastewater testing complements human testing to help identify trends.

“Can we predict number of cases? No,” he said. “Can we say that a particular area is a hotspot based on wastewater concentration? Sure.”

Testing sewage for SARS-CoV-2 is not unique to the northern part of the state. Officials have been testing wastewater in Southern Nevada since last March.

Daniel Gerrity, principal research microbiologist for the Southern Nevada Water Authority, said Tuesday that it is still too hard for him to say confidently whether wastewater testing in Southern Nevada can give public health officials a head start on identifying infections.

“Wastewater gives us a snapshot of what’s happening right when we collect that sample, so we’re confident in that,” he said.

But, he said, it’s hard to compare that to data sets from testing of individual people because there can be a discrepancy between infection dates and reporting dates.

Contact Blake Apgar at bapgar@reviewjournal.com or 702-387-5298. Follow @blakeapgar on Twitter.