Tests of wastewater from across Maine have shown a steady increase in COVID-19 cases in recent months, offering additional, localized insight into the spread of the coronavirus.

Some Maine colleges, meanwhile, have successfully used the stuff flushed down the toilet to detect and isolate cases before they lead to larger outbreaks. St. Joseph’s College, for instance, has found infected-but-asymptomatic individuals on campus after following the virus trail to specific buildings.

“The wastewater has given us the tip off,” said Oliver Griswold, a spokesman for the small, private college in Standish. “In both of the two outbreaks we’ve had, we heard from the wastewater first.”

Still, it would take more frequent and robust screening to turn the state’s massive network of toilets into an early warning system for infection spikes.

Individuals infected with the virus that causes COVID-19 shed fragments or genetic “markers” of the virus in waste. While research suggests the amount of active or live virus in feces is low, laboratories can detect and then amplify active or inactive markers as another way to detect trends before they begin showing up in the daily case counts.

“This is allowing us to get a finger on the pulse of what’s going on in the community,” said Yolanda Brooks, an assistant professor of biology at St. Joseph’s College whose team has been testing samples from the Portland Water District, Yarmouth and the campus community.

The Portland Water District has been collecting weekly samples from its East End treatment plant in Portland and its Westbrook/Gorham facility for COVID-19 testing since July. Test results show levels of virus materials increasing starting in September and spiking in late-October. That correlates with surging case numbers within surrounding communities in recent weeks as Maine has seen the highest rates of infections and deaths since the pandemic arrived in Maine in March.

Traces of the virus in samples from the Westbrook/Gorham treatment plant, for instance, increased by a magnitude of 10 between Sept. 1 and Nov. 3. While Brooks said federal officials caution against estimating the number of infections in an area based on wastewater results, she noted that Westbrook/Gorham had just a handful of cases on Sept. 1 and roughly 50 as of last week.

“It does confirm a correlation,” said Brooks, who has a doctorate in microbiology and a background in studying fecal pollution.

Other towns in Maine, including Yarmouth and Augusta, also have contracted with St. Joseph’s College or a national lab to conduct testing.

St. Joseph’s internal testing program, meanwhile, illustrates the enormous potential for wastewater monitoring.

Because St. Joseph’s has its own wastewater treatment system serving a relatively small population, staff have been able to use the testing results to zero in on clusters of cases in individual buildings.

The process begins by collecting a series of samples from each of the three wastewater “lift stations” that serve different sections of campus. By analyzing those results, Brooks and her colleagues can see whether levels of the virus’s genetic markers have changed since the previous tests and, in the event of an increase, order building-level testing in that zone.

The college can then test individuals residing or working in buildings that have elevated levels of the virus markers. The vast majority of the students infected with COVID-19, to date, were asymptomatic but potentially contagious, so wastewater testing enabled college health officials to find and isolate them, said Griswold, the college’s spokesman.

“The early warning piece of it has given the whole campus a sense of we are going to know early what is going on campus,” Griswold said. “Whereas if you are just doing individual testing, you are going to know only when you have a problem, not before you have a problem.

St. Joseph’s College has had 15 confirmed cases during the past two weeks, prompting administrators to transition all students to remote learning and send them home early this week before the Thanksgiving break.

Three campuses of the University of Maine System – Orono, Fort Kent and the University of Southern Maine – also have been testing wastewater for COVID-19 since September. More recently, the UMaine lab where the test is done recently started analyzing wastewater from the town of Orono and is working with the University of New England in Biddeford on testing.

Both the UMaine and St. Joseph’s labs use a testing system developed by IDEXX Laboratories in Westbrook. The veterinary services company has also partnered with the Maine Center for Disease Control and Prevention to provide the equipment and materials used to conduct thousands of COVID-19 tests daily on nasal swabs collected from individuals.

Robert Wheeler, associate professor of microbiology who leads the testing effort from his Orono lab, said virus levels in wastewater have been rising since September but the increase has not been steady. Wheeler noted that the various campuses have had lower numbers of infections among students and staff than their surrounding communities.

The combination of sensitive testing technology and low virus prevalence rates allows them to detect slight changes.

“If we don’t have any known cases but we are seeing the virus in the wastewater, that is a disconnect and triggers a discussion” about where to direct additional testing, Wheeler said.

Like Portland, UMaine’s testing is only done weekly, which limits the ability to quickly detect trends. Wheeler said his lab hopes to expand capacity this spring.

“Ideally we would be testing all of these places every day,” he said. “The University of Maine doesn’t quite have all of the resources to do that and the State of Maine hasn’t provided those resources as of yet.”

Scott Firmin, director of wastewater services at the Portland Water District, said it would be up to the member communities about whether to increase testing frequency. Tests cost $120 per weekly sample during the first, three-month period of the pilot project, but the district has since extended the agreement with St. Joseph’s College lab at $380 per sample.

With all of the focus on fragments of the virus in wastewater, Firmin stressed that drinking water is safe.

“We use dual water treatments, ozone and ultraviolet light, that effectively inactivate viruses and kill pathogens,” Firmin wrote in an email. “COVID-19 is mainly thought to spread between people who are in close contact with one another, not through water, according to the CDC. The EPA states that the presence of the COVID-19 virus has not been detected in drinking-water supplies and based on current evidence the risk to water supplies is low.”