Sewage samples show COVID levels dropping in New Haven area


The latest wave of COVID-19, driven by the contagious BA.2 and BA.2.12.1 subvariants, is showing signs of receding, with declining levels of the disease being detected in sewage.

Yale University researchers collecting samples at a New Haven water treatment facility found significantly fewer incidences of the virus in recent samples than a month ago. As of June 6, there were about 30 cases per 100,000 people in the New Haven area detected, up from about 60 cases per 100,000 people in mid-May.

The data reflects trends captured in state testing efforts. Connecticut’s seven-day mobile positivity rate fell to 7.5% on Monday, from a high of 14% a month ago.

“It’s been going down for at least 20 days,” said environmental engineering professor Jordan Peccia. at Yale who runs the sewage testing there. “If there’s one thing we know, it’s that sewage isn’t bad. We’ve compared it with all sorts of information on hospitalizations, cases, etc., and it still matches up well.

“Historically, summers tend to be our lowest time for COVID rates, and winters are our highest,” added Dr. Manisha Juthani, the state’s public health commissioner. “We expect similar trends to continue, but remain vigilant for the emergence of new variants with different modes of transmission.”

With the rise of rapid home tests and fewer people performing PCR tests that feed into state positivity data, sewage detection has become increasingly important for tracking COVID trends and predicting epidemics.

Until late last year, the state was paying Yale researchers to track the spread of COVID at several large wastewater treatment plants that served more than a million people in the state. These samples closely tracked the ebb and flow of the virus in many of the state’s most populous communities, including Bridgeport, Stamford, Norwich, Hartford, Waterbury, Danbury and New London.

But the state contract under which this work was done ended in October 2021, and when it did, the public health data that was being collected was cut off in many places.

Alessandro Zulli, who holds a doctorate from Yale. environmental engineering student, processes samples taken from a New Haven sewage treatment plant. “We were surprised by the results,” Zulli said. “In March 2020, we spent two weeks trying to get this process to work. And then once we had a curve, we saw that it followed almost exactly what the state was putting in place.” Yehyun Kim /

Yale is currently testing samples only from the East Shore Water Pollution Abatement Facility, which serves New Haven, Hamden, East Haven and parts of Woodbridge. A private donor, Jonathan Rothberg, has funded the Yale lab’s work since state support ended.

At this time, state officials have no immediate plans to resume funding for the Yale Sanitation Project. They encourage cities to participate in a new effort by the Centers for Disease Control and Prevention, which allows officials to provide data on treatment plants. The data is shared and analyzed on a CDC website.

So far, 11 communities have joined the program – three in New London County, one in Windham County, two in New Haven County and five in Fairfield County. But there is no data posted for two of the sites, and others have not consistently reported COVID levels.

“Yale’s information is incredibly useful and informative. But when we started working with Yale, there was no CDC infrastructure when it comes to this information, and now it does exist,” said Max Reiss, a gatekeeper. – Governor Ned Lamont’s word: “Obviously, attendance may not be at a significantly denser high level. However, getting different snapshots in the state certainly provides an informative perspective on what the virus is doing in various locations.

“We continue to work with different municipalities to encourage other regions to take as broad a view of the state as necessary,” Juthani added. “Because the CDC is robustly funding this program and allowing as many municipalities as we want at this time to enroll, we are investing our efforts in getting cities to participate.”

Some other states have stepped up their local wastewater treatment efforts. In New York, Governor Kathy Hochul announced late last year that the state would partner with Syracuse University to continue its wastewater analysis. At least 20 counties participated in wastewater monitoring.

Alessandro Zulli, who holds a doctorate from Yale. environmental engineering student, processes samples taken from a New Haven sewage treatment plant. After measuring the samples, the team can estimate the number of people in New Haven who have COVID. Yehyun Kim /

“Sewage monitoring can provide up to three to five days of early warning that COVID-19 cases are rising or falling in a community, and studies have shown it can be used to detect variants of the virus. through the sequencing of wastewater samples, once identified,” Hochul said in a press release. “We are learning new things about the COVID-19 virus every day, and to stay one step ahead, we had to adopt new and innovative prevention and detection strategies.”

Wastewater monitoring is important even during lulls in coronavirus cases, Peccia said, because there are clues about when the next surge might start. The Yale lab has been tracking wastewater since March 2020.

“There are times when everyone cares about COVID, and there are times when no one cares about COVID. We are entering one of those times where nobody cares about COVID,” he said. “But the only thing we know is that it will probably be back. It will probably be [increasing] in autumn.

“I guess in July and August, nobody’s going to look at our results. Few people are going to test in the state; we’re going to be happy. Then some variation or something is going to happen, outbreaks are going to happen and the people are going to care again. You need this information to stay alert when no one is looking. You get an early indication of the return date because it is so difficult and expensive to expedite these test programs.

With the help of the private donor, Yale will continue its surveillance until at least next June. The lab plans to launch a new website with its wastewater updates later this summer.

“If COVID goes away or gets really low, that’s when we need sewage – some level of ongoing monitoring to make sure it doesn’t come back, or if it comes back, we have an early warning of it,” Peccia said. “This is where sewage really shines.”

Writer Andrew Brown contributed to this story.


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