New London — The city has joined a nationwide volunteer testing network that uses wastewater to help track the presence of the virus that causes COVID-19.

Earlier this month, a contractor for the Centers for Disease Control and Prevention started taking twice-daily samples from the city’s wastewater system as part of the National Wastewater Surveillance System, said Joe Lanzafame, the city's director of public utilities.

The CDC’s initiative, launched at the beginning of the pandemic, aims to provide an early warning system to communities about a possible surge in COVID-19. Health officials in turn can use the information, combined with other data, to help make decisions on items such as public outreach to encourage testing or mask wearing.

Hundreds of other cities nationwide are using the testing method as a barometer for a potential outbreak as the number of people seeking lab tests drops and at-home testing increases. The results of at-home tests, however, cannot be tracked by health officials. Wastewater is seen as an indicator of cases as people infected with COVID-19 shed the virus in their feces.

“What we learned through the pandemic so far is that wastewater is something that is not susceptible to the number of people going out and getting tests. It really is a reflection on what might be happening on a population level,” Dr. Manisha Juthani, commissioner of Connecticut’s Department of Public Health, said in a recent interview with The Day.

Wastewater tests, in combination with other data, give health officials “our best indicator, particularly on an uptick of an upcoming surge or not in a given community and in our state,” Juthani said.

The CDC has looked to DPH for help enlisting municipalities with wastewater treatment plants. The DPH is not involved in data collection or analysis but is monitoring the publicly available wastewater test results that became part of the the CDC’s COVID Data Tracker in February.

Five municipalities in Connecticut had enrolled in the system as of Friday, the CDC website shows. More are expected to participate and join the CDC's goal of 500 testing sites nationwide.

Norwich Public Utilities will begin testing in the coming weeks, said NPU spokesman Chris Riley. Norwich and New London had been submitting wastewater samples as part of a Yale University program that was scaled back in the fall when state funding evaporated.

Riley said NPU was contacted by the state Department of Health to participate in the CDC program.

New London sewage includes wastewater from parts of Waterford and East Lyme. The Norwich sewage treatment plant serves parts of Franklin, Sprague, Preston, Bozrah and Lisbon.

“NPU is pleased to participate in such an important study and is committed to supporting the overall public health of our community whenever possible,” Riley said.

Derek Albertson, superintendent at Montville’s Water Pollution Control Authority, said Montville has submitted test results to the Microbial Analysis, Resources and Services (MARS) facility at the University of Connecticut. He expects that data will be submitted to the CDC’s data to help create a larger picture of community levels of COVID-19. About 64% of Montville is served by sewers. Initial sampling, Albertson said, indicates very low levels of COVID-19.

Patrick McCormack, director of health for the Uncas Health District, which includes Norwich, said the testing would provide data weeks in advance of a surge of COVID-19 and its variants. He added that the data could help prompt the health department to perform community outreach about prevention strategies.

Earlier this month, New London’s City Council hosted an update from Stephen Mansfield, director of health for the Ledge Light Health District.

Mansfield explained that the CDC in February announced new metrics to help guide mitigation efforts, relying more on significant outcomes from COVID-19 rather than infections alone.

The CDC assigns counties in states with a color-coded chart that Mansfield said “paints a more realistic picture of where we stand.” The new metrics take into consideration the number of infections, number of new hospitalizations and availability of hospital beds.

All of Connecticut was in the low-risk category as of Friday. Noting that “COVID-19 has receded but not disappeared by any means,” Mansfield said the CDC still recommend people with symptoms, a positive test or exposure to someone with COVID-19 should wear a mask.

Staff writer Claire Bessette contributed to this report.

g.smith@theday.com