A wastewater sample is collected at the University of Maine to test it for the presence of COVID-19 in September 2020. Credit: Courtesy of University of Maine System

Bangor will join a growing number of Maine communities testing their wastewater for the coronavirus as a virus surge driven by the highly contagious omicron variant continues and the state’s daily case counts become a less reliable indicator of the coronavirus’ spread.

The city tried to test its wastewater for COVID-19 earlier in the pandemic, but halted those efforts. Bangor is working with the Maine Center for Disease Control and Prevention to start testing again, said Amanda Smith, the city’s director of water quality management.

Wastewater testing can show how widely the virus is spreading in the general population, rather than only in those being tested for it. Plus, it can be an early indicator of a surge of positive tests and hospitalizations in a community.

Wastewater testing is expanding in Maine as the state’s daily case counts capture a smaller portion of virus cases, many discover they’re infected using at-home tests that aren’t reported to the state, and others simply don’t get tested for a variety of reasons. The state also faces a growing backlog of 56,000 positive test results that it hasn’t processed.

The Maine Department of Health and Human Services announced Wednesday that more than a dozen communities would begin testing wastewater for the coronavirus.

Wastewater samples contain a much more varied group of the population than regular testing, Maine CDC Director Nirav Shah said Wednesday. People are part of the sample regardless of a decision to get tested, vaccine status or symptoms, Shah said.

“There’s always a sense that you are not seeing the entire thing,” Shah said. “Wastewater, in that respect, is the equalizer because it samples from the entire population.”

Shah said the Maine CDC would use the samples it collects to track local trends. It plans on alerting local hospitals and providers in the area if wastewater testing detects sharp spikes in cases, he said. A spike could portend a future need for hospital beds.

Penobscot County, in which Bangor is the service center and largest city, has seen nearly 2,000 recorded COVID-19 cases this month, though its rate for that time has been among the lowest for any county in the state. 

There had been attempts earlier in the pandemic to test wastewater from Bangor’s treatment plant for the presence of the coronavirus, but that effort stopped due to belief that stormwater would dilute the samples, Smith said. Bangor’s is one of about three dozen combined sewer and stormwater systems across the state.

“During snow-melt and wet-weather events, daily flows can reach 43 million gallons per day,” Smith said. “The exact degree to which the sample has been diluted is difficult to estimate from one sample day to the next.”

The new testing program will account for this dilution by comparing concentration of the virus to other known fecal indicators, she said.

When the program resumes in Bangor, it will not be the only entity conducting testing in the area.

The University of Maine System has tested wastewater at four of its campuses — the flagship in Orono, the University of Southern Maine’s Gorham campus, Fort Kent and Presque Isle — as well as within the municipalities of Orono and Farmington since testing began in the fall of 2020.

It is all coordinated by Robert Wheeler, a professor of microbiology at UMaine, who began the testing program due to a shortage of conventional tests. He noted that research at the time, both domestically and outside the U.S., had shown that wastewater results could precede diagnosed COVID-19 cases in a town or city by around a week.

“We thought using wastewater testing may be a good early warning indicator for a rise in the prevalence of the virus,” Wheeler said.

The university system’s wastewater testing is primarily a surveillance tool. It allows it to see the prevalence of the virus on campuses to inform policymaking.

Over time, the system has simplified the process of collecting wastewater, Wheeler said. The new process is cheaper and less labor intensive, something especially important during current personnel shortages being across the state, he said.

Amid last spring’s vaccine push, Wheeler said he once thought that the testing could become unnecessary. But then came the delta variant, and eventually omicron.

Now, he thinks such testing will likely take on a more important role.

“I think it’s clear that we are going to need to be on our toes for checking surveillance of SARS-CoV-2,” Wheeler said.