A wastewater sample is collected at the University of Maine to test it for the presence of COVID-19. Credit: Courtesy of University of Maine System

ORONO, Maine — Low levels of SARS-CoV-2, the virus that causes COVID-19, were found in testing samples of Orono’s wastewater last week, the University of Maine said.

While the weekly testing shows only low levels of virus fragments, any detectable level could be a warning signal of a potential outbreak to come, as people can shed the virus in their stools before developing symptoms.

Increasing levels of virus fragments also can be found in wastewater up to one week before cases begin to rise in a community, UMaine Associate Professor of Microbiology Robert Wheeler, PhD, said.

The SARS-CoV-2 virus has a genome that includes all genes that the virus needs in order to cause disease, he said. When the virus disintegrates, the genome can be broken into fragments.

For that reason, results from wastewater testing don’t indicate if the infectious virus is currently in the wastewater, but rather the presence of virus fragments.

The University of Maine System has been doing weekly testing of wastewater samples at the three campuses that house more than three-quarters of its residential student population — in Orono, Fort Kent and Gorham — since mid-August.

The tests were coming back consistently negative until Oct. 28, when results showed that Orono’s wastewater indicated a “low but clearly detectable level” of the virus with 7,600 viral equivalents per liter, the university said.

While wastewater samples tested on Oct. 30 came back negative, that doesn’t necessarily mean that the water is free of virus fragments. Due to testing limitations, the samples can only determine if the wastewater has levels above 5,000 per liter, Wheeler said.

This means that even if testing samples come back negative, fragments of the virus could still be present at lower levels.

“The reason why we started doing the wastewater testing is to really have a sampling of the whole community,” he said.

At Saint Joseph’s College in Standish, the presence of the virus in wastewater was the first sign of a COVID-19 outbreak on campus earlier this month, according to Maine Public. Nine students tested positive and the college temporarily shifted to remote instruction as a result.

If wastewater virus levels are consistently increasing over time, that could be a yellow or red flag that the community should be doubling down on preventive measures, Wheeler said.

Wheeler supervises the wastewater testing in his laboratory and is a member of both the university’s scientific advisory board and a faculty wastewater testing group.

But it’s hard to predict if the levels will continue to fluctuate. It’s possible that the levels will stay low or remain undetectable, but they could also increase in the coming weeks as Maine experiences a surge of COVID-19 cases.

Nirav Shah, director of the Maine Center for Disease Control and Prevention, recently warned that Maine is experiencing “forceful and widespread” community transmission of the coronavirus throughout the state amid the recent spike in cases — which could continue for some time, he said.

Since the start of the fall semester, the University of Maine System has maintained relative control over the virus on its flagship campus with preventative strategies such as routine testing and wastewater sampling to prevent an outbreak.

UMaine reported one active case of COVID-19 when the wastewater sample report was released Friday.

The wastewater sampling is being conducted through a partnership between UMS and the town of Orono. In August, Orono also passed an emergency mask-wearing ordinance to help slow the spread of the coronavirus as much of the university population returned for the fall semester.

“In the town of Orono, we are committed to providing our citizens and guests with the resources and information they need to safely live and work in our community,” Orono Town Manager Sophie Wilson said. “Cases of infection are growing throughout Maine and detecting the presence of the virus in our wastewater serves as a reminder that we must all do our part to limit the spread of the disease.”