TRAVERSE CITY — Left-over grant money let operators at Traverse City’s wastewater plant test more sewage samples for the virus behind COVID-19.

A pilot project originally set to wrap at the end of December carried on for a few more weeks after the Michigan Department of Environment, Great Lakes and Energy gave cities that still had the funds left the OK, said Art Krueger, Traverse City’s municipal utilities director. The notice came a little late — sometime in mid-January — but a deep-freeze cooler kept the samples good to test.

He’s hoping the extra data can be useful in tracking trends in virus levels.

“If you were going to try to capture any trends, it’s just always better to have more data to look at, so I think overall it’s a good thing,” he said.

The weekly numbers from the start of January through Feb. 15 show somewhat falling levels, save for one major outlier, said Dan Thorell, Grand Traverse County Health Department’s director of environmental health. The numbers come from a pared-down list of collection sites compared to the October-through-December period, and Krueger said he doubts they capture any effects the vaccine roll-out had on the spread of the virus.

Traverse City was one of dozens around the state to get a grant from the state to look for the virus SARS-CoV-2 in sewage, as previously reported. The idea was to use a proven technique to track the rise and fall of COVID-19 infections by tracking virus levels in wastewater. It’s used elsewhere in the world but not as much in the U.S.

People shed the virus in their feces several days before they show symptoms, so wastewater surveillance gives an early warning of an outbreak if the collection site is for a contained area — say, a congregate care facility or university dorm.

Viral levels in sewage should drop as containment measures pay dividends, and numbers that continue to rise could indicate problem areas.

Plus, anyone who uses the public sewer system is providing anonymized samples, so epidemiologists have a much broader idea of viral spread than nasal swabs alone can provide.

So with a $172,000 grant, the Traverse City Regional Wastewater Treatment Plant got a digital droplet polymerase chain reaction machine and that special deep freezer. Thorell said the machine looks for a certain genetic phrase found only in SARS-CoV-2 and can quantify the number of copies it finds.

Data from Traverse City was mostly too broad to make predictions of outbreaks, but its participation helped push the science forward on using wastewater to track outbreaks of communicable diseases, Thorell said.

“We’re generating data here, we’re doing work and analyses and when you do that, the scientists out there that are looking at this can make some definite conclusions about what worked and what didn’t,” he said.

The study will also help determine whether the virus can survive in wastewater or not, Thorell said. Sewage is filled with household chemicals that could kill SARS-CoV-2.


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