Health Care

Burlington ramps up free testing after wastewater shows Covid spike

Matt Dow, wastewater facilities manager, samples wastewater for Covid at the New North End plant. Photo by Katya Schwenk/VTDigger

Free Covid-19 testing is being offered in Burlington’s New North End Thursday and Friday, after the city’s Covid-19 wastewater detection system picked up presence of the virus in that part of the city. 

The testing at the Robert Miller Community and Recreation Center is available to anyone who lives or works in the New North End, according to Mayor Miro Weinberger’s office.

The city’s Covid-19 wastewater detection system can identify the virus in Burlington’s sewers three to seven days before it shows up in tests on people.

Last Friday, as coronavirus cases rose in Chittenden County, Burlington’s Water Resources Division saw the first signs of higher Covid-19 levels in the city’s wastewater.

Since August, the city has been monitoring sewers for traces of the coronavirus, looking for signs of an outbreak. Sewage testing has emerged nationwide as a promising tool for early detection of coronavirus spread. The virus can be detected in an infected person’s stool days before they are symptomatic or even if they never show symptoms at all. When strands of coronavirus RNA are discovered in wastewater, they can serve as an initial indicator of virus cases.

For weeks, the concentration of the virus in Burlington’s three wastewater treatment plants — measured in genomes per liter — had remained stable, hovering around zero with occasional isolated upticks. In the last week, though, the plant that serves the city’s New North End has seen a sharp rise in viral concentration.

Gaps in the science mean that the spike, which appears visually dramatic, cannot be extrapolated to a specific number of cases, nor any particular rate of increase. But the upward trend was exactly what Brian Lowe, the city’s chief innovation officer, and his team working on wastewater surveillance at the Water Resources Division, have been watching for.

“What we know,” he said, “is that there is a growing amount of viral RNA in the wastewater in that catchment area. And that it was unexpected. And that it can’t be explained by existing case data.”

In other words, the rise detected in the New North End’s wastewater signals that Burlington’s actual case count may be higher than clinical testing data currently shows.

That’s because case counts from clinical data, in theory, can lag behind detection in wastewater. “You have to get symptomatic. You have to see a doctor. You have to get a test, and you have to get those test results back,” Lowe explained. “And that can take time.”

“Theoretically, you get up to a 7-day lead time [in wastewater] before you get an increase in active cases that are diagnosed,” said Isabella Martin, a medical microbiologist and lead researcher on Dartmouth-Hitchcock Medical Center’s wastewater testing project, which has partnered with Burlington on the program.

But it's unclear on whether or not that lead time works in practice, Martin said. And they have no firm conclusions yet.

"The jury's still out on how useful wastewater testing will be,” she said. “The next question you have to ask is, well, say we do see a spike in wastewater, and we don't have a big spike in human cases yet. What actions are going to be taken in response to that?”

In Burlington, at least, the city moved quickly to respond.

The city put up flashing signs this week on North Avenue, warning North End residents that the virus risk may be heightened. And on Wednesday, the mayor’s office announced it would open pop-up testing sites in the vicinity on Thursday and Friday.

“Those readings were an additional data point confirming we are in this period of elevated risk,” Burlington Mayor Miro Weinberger told VTDigger. He said hoped the city’s communications in the last few days would “get people’s attention, and people to really understand that we have to be extra vigilant right now, in Vermont and in the city of Burlington.”

“That’s why we put the system in place,” Lowe said. “The whole hope of the program is to identify a developing risk and to take proactive action.”

Chittenden County has had the steepest increase in recent cases among the 14 counties in the state. 

Covid-19 testing is free to the public. Residents must reserve a spot through Garnet Health, not the Vermont Department of Health’s website. Testing will be conducted between 1 and 4 p.m. on Thursday and between 9 a.m. and 1 p.m. on Friday at the Miller Center, located at 130 Gosse Court, Burlington. 

The sewage testing costs are being covered by the city through emergency funding that was authorized by the city council in March, according to the mayor’s office.

In the coming days, more wastewater and clinical test data will clarify what this early alarm bell may mean for Burlington. And across the state, other communities are looking to sewers for answers, as Vermont scrambles to get the coronavirus under control. 

Burlington began testing wastewater in early August, partnering with researchers at Dartmouth-Hitchcock as well as a commercial lab. At that time, cases were low, but the return of students to the city’s universities loomed. This was a key moment, Lowe said. People may continue to shed viral RNA even after they are no longer infectious, so it’s best to begin testing when the prevalence of infections is low. 

The city was also primed for wastewater testing because the sewage system is split into three sections, each covering a specific geographic area. If the virus is detected at one of the plants, it can be located, at least initially, in that region of the city—as in the case of the city’s North plant, which serves only the city’s New North End neighborhoods.

Still, Lowe noted, “Burlington is so small that we don’t expect any risk to be geographic for long.” And there are other limitations, too: Somewhere between 40 and 80 percent of people shed coronavirus RNA through their stool when infected, meaning that not all cases will be detectable in wastewater. 

Or, cases might be missed by the samples entirely. “There’s no way to sample every drop that comes through,” said Matt Dow, Burlington’s wastewater facilities manager. The goal of the program, he explained, is to collect “a bunch of little grabs that are representative.”

Burlington regularly samples the wastewater for phosphorus, Dow said, as well as for the presence of E. coli bacteria. But this is the first time Burlington has used sampling to look at a public health concern like coronavirus—though historically, sewage surveillance has been used to track diseases like polio and cholera.

On Tuesday, Dow was collecting one of the city’s thrice-weekly coronavirus samples at the North Plant. This time, though, was different. He and the water resources team wanted to narrow, geographically, the rise in cases in Burlington’s New North End.

To do that, Dow cracked open the sewer hole where sewage lines from two halves of the North End, split approximately to the east and west by North Avenue, come together. In each, he placed a tube that, over a 24-hour period, will suck up 99 small samples of wastewater, yielding a 120-milliliter composite sample that the city sends out for testing. The results will help the city determine if the rise in viral load in the water is originating, specifically, from one of those two regions in the North End.

There are reasons, though, why the virus may just have been more quickly detected in the North End plant, as compared to Burlington’s downtown wastewater: the North plant takes in about a quarter as much water as the city’s main plant, and it serves an almost exclusively residential area. “It's much more stable, and smaller, and it’s easier to see if there's something happening,” Lowe explained. 

“We've detected [the virus] here first, but that doesn't mean that it's only here, or that it would stay in this area,” he said.

The New North End wastewater treatment plant. Photo by Katya Schwenk/VTDigger

Following Burlington’s lead, other communities in Vermont have launched their own wastewater testing initiatives. Martin and the other researchers at Dartmouth-Hitchcock Medical Center are also working in ten other municipalities across Vermont and New Hampshire to conduct wastewater testing.

Wastewater testing has become particularly popular with colleges and universities. Last month, NPR reported that at least 65 schools across the country are testing their students’ waste for the virus to supplement clinical testing. And in Vermont, that number is rising. 

Norwich University, a small military college in Northfield, announced this week that it was launching a program to test wastewater on its campus. Small schools like Norwich, explained Tara Kulkarni, a professor of environmental engineering who is leading the project, can particularly benefit from sewage testing: Unlike in larger municipalities, colleges can routinely test sewage systems for individual dorms or buildings, allowing for more targeted action if the virus is detected.

At Norwich, students are helping to create a testing program and conduct sampling for the campus, with hopes to have a protocol in place by the time students return from their winter break in January. “Our main goal for this work is to keep our campus community safe,” Kulkarni said. 

But Norwich’s project, she said, could also serve as a model for wastewater testing in Vermont’s rural communities and schools, which often have more limited access to health care and clinical testing. “Our hope is to really be a hub for that testing,” she said. “Being there for that population is important.”

“One of the harder things about this whole [effort] is there's a lot more attention on bigger schools and bigger urbanized areas, because those are the population centers,” Kulkarni explained. “But a lot of these outbreaks are also impacting rural areas, who don’t always have the means to do testing.” 

Automated water samplers, like the kind Burlington is using to test its wastewater, can cost thousands of dollars each, for instance — prohibitively expensive for many communities, including Norwich. To get around the expense, Norwich students have built their own, cost-effective automated sampler, which Kulkarni said will be tested out in the field for the first time this week, and could be replicated elsewhere.

There are unique challenges, though, for sewage testing in rural areas. Fewer residents will have homes that flush wastewater to a centralized treatment plant, instead relying on personal septic systems. Testing, in that case, would be less representative, said Kulkarni, but “at least they would have some data, versus none.”

Also on the minds of researchers are the privacy implications of such testing. While the virus cannot be traced back to specific individuals or homes when it’s detected in a large wastewater facility, Kulkarni said it’s important to keep that boundary in mind when testing in smaller communities. “You want to be mindful you're not infringing on people's individual rights, and that [testing] is still a composite of the region, or the area, or the building, in the case of our campus,” she said.

Norwich University is looking now to partner with St. Michael’s College and the University of Vermont to collaborate on wastewater testing efforts, and consider federal grant funding. Like researchers across the state, they hope that keeping their eyes on the sewers will give them an edge, as the pandemic continues relentlessly on.

Grace Elletson contributed reporting

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Katya Schwenk

About Katya

A native Vermonter, Katya is assigned to VTDigger's Burlington Bureau. She is a 2020 graduate of Georgetown University, where she majored in political science with a double minor in creative writing and Arabic. She was a contributing writer for the Indypendent in New York, an assistant editor at the Boston Review and a writer for the Scoop News Group and Morocco World News in Rabat. 

Email: [email protected]

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