As it weighs its response to the ongoing coronavirus pandemic, the city of Somerville is turning to science — and its sewers.
By testing raw sewage for coronavirus particles at 10 sites throughout the city, Somerville's mayor said he hopes to "get ahead of the virus."
The initiative is a partnership between the city, the engineering firm Stantec, and a research team at Northeastern University led by Ameet Pinto, an environmental engineer and microbiologist.
Curtatone hopes it will provide coronavirus data more reliably, quickly and affordably than individual testing can.
“You can’t have enough conduits for data when you’re taking on a pandemic that continues to evolve and change,” Curtatone said. “Contact tracing is not where it should be; traditional PCR testing is not where it should be.”
Pinto was emphatic that his team’s aim is to complement, not replace, the clinical, nose-swabbing approach we’ve come to know.
That said, sewage-based testing does have advantages: “Getting a pooled sample is inherently faster. You don’t have to wait for 10,000 different tests. You can have this one test to get a broad snapshot.” The first samples from Somerville are set to arrive in Pinto’s lab Friday. He expects his four-person team will be able to generate results within two days.
In its basic contours, the Northeastern team’s approach isn’t new. It has been used to track the polio virus for years, for example. There, it’s shown impressive results, he said: “There are some estimates that suggest that this [approach] might be able to pick up one infected individual among 10,000.”
And the method is already being used to track coronavirus at the state’s Deer Island Treatment Plant, in a partnership between the Massachusetts Water Resource Authority and Biobot, a private biotechnology firm based in Cambridge. (The MWRA shares the resulting data on its website.)
But Pinto's hope is that his team's more granular approach could provide useful, even life-saving, insights.
The 10 initial manholes in Somerville were chosen for their ability to capture localized outbreaks among sensitive populations: from neighborhoods favored by college students to those containing public housing or senior centers.
Pinto said in that way, Somerville’s plan is more analogous to a similar initiative undertaken at the University of Arizona than to the MWRA effort.
“They’d been testing ten dorms, a couple of times a week,” Pinto said. Last week, university researchers detected coronavirus particles in sewage from a single dorm. “The next morning… they went in, quarantined 340 students in that dorm and did rapid tests on all of them.” The tests revealed two asymptomatic carriers of the virus, who were quickly removed.
“The next day, the dorm’s sewage was no longer positive,” Pinto said, calling it a “beautiful demonstration” of the approach’s potential.
The results will be somewhat less definitive in dense Somerville neighborhoods, Pinto conceded. His team has sought ways to account for dilution by rain, rates of viral decay and the “very dirty matrix” of a municipal sewer system to produce reliable numbers.
But he hopes that the approach can inform rapid and practical responses by city officials. “In my mind,” Pinto said, “I think about [questions] like, where do we put up our pop-up testing centers?”
Somerville’s approach to the pandemic has been more cautious than the state’s at large. In July, the city pushed the brakes on advancing to "Phase 3" of reopening, citing rising case numbers. Then in early August, its school officials were among the first to counter state guidance and commit to a remote start to the school year.
But that’s beginning to change. On Thursday, Curtatone announced plans to allow more businesses — including fitness clubs, film productions and educational programs — to resume business in Somerville starting on September 8, albeit under strict safety protocols.
That’s in spite of the fact that the city’s daily incidence rate of COVID-19 is on the rise. Curtatone said that while officials are working hard to gather data, “we need to be ethical, I’d submit, in how we use [it]. It can’t just be a means to roll back or halt activity.”
Curtatone said the phased reopening reflects, in part, a sense that many of the city’s businesses are “taking it on the chin” — and that operating revenue, as well as financial support, will be necessary to prevent widespread closures.
But Curtatone added that neither the promising project with Northeastern nor this business-related reopening are signs that schools could reopen sooner than later. Pointing to school-related outbreaks in the state of Georgia and in Israel, Curtatone said, “we need to pay close attention to those lessons.”
He hopes that Pinto’s team will add school-based testing sites when Somerville does return to a hybrid model — but the timing of that move is yet unknown.