Detecting the virus in wastewater is more important than ever as fewer tests are reported to the state.

Wastewater from much of eastern Massachusetts is analyzed at the Deer Island Wastewater Treatment Plant. David L Ryan/Globe Staff

In recent weeks, Massachusetts has seen a spike in positive COVID-19 cases. Will this trend continue? Sewage data, a powerful tool for predicting future cases, suggests it will.

The level of COVID-19 in wastewater is an important early warning sign, as the process generally picks up infection before those who have the virus can confirm it with an actual test. In this phase of the pandemic, more and more residents are relying on rapid tests to take at home. These findings are not typically reported to health authorities, further increasing the importance of wastewater data.

COVID-19 levels detected at the Massachusetts Water Resources Authority’s Deer Island wastewater treatment plant are now back to levels not seen since late January. The Boston Globe reported.

“The increase we’re seeing is real and ongoing,” said Andrew Lover, an assistant professor of epidemiology in the School of Public Health and Health Sciences at the University of Massachusetts Amherst globe. “Nationwide, we’re seeing quite a lot of viruses in sewage.”

On Thursday, the Massachusetts Department of Health reported 4,957 new confirmed cases of the virus. The seven-day moving average of confirmed cases is now 2,985.7. That number has fallen slightly since May 15, but has been rising steadily since mid-March.

The MWRA Deer Island facility analyzes wastewater from 43 communities including Boston, the globe reported. The test identifies the number of SARS-CoV-2 RNA copies per milliliter of water. The data is split between the southern and northern regions of the MWRA system.

In the northern region, the seven-day average on Wednesday was 1,273 RNA copies/mL. That number peaked on January 5 at 8,644 copies. The lowest copy number was identified on March 9th at 101 RNA copies/ml globe reported.

In the southern region, the average on Wednesday was 1,332 RNA copies/mL. The lowest values ‚Äč‚Äčthis year were observed on March 1st at 92 copies/ml.

Some in the state are sounding the alarm, pressuring officials to reintroduce certain pandemic response tactics that have fallen by the wayside. On Wednesday, a group led by the Massachusetts Coalition for Health Equity called on Gov. Charlie Baker and state agencies like the MBTA to issue advice recommending that people wear masks indoors and avoid large gatherings.

Coalition members, which include healthcare workers, public health advocates and community leaders, cited the fact that not as many positive tests are reported to the state. This could increase the importance of wastewater analysis.

“Everything is on the rise and it’s happening pretty fast,” Jon Levy, chair of Boston University’s Department of Environmental Health, said during a virtual news conference. “But it’s just the tip of the iceberg, and we all know that a lot of testing is currently being done at home (and) not all positive results are reported to the state.”

Across the country, wastewater analysis appears robust at the state level, but is weakening at the local level. Overall, 92 percent of state health officials and just 38 percent of local agencies had monitored sewage for the virus, according to an April report by the Rockefeller Foundation, the Pandemic Prevention Institute and Mathematica.

Of course, collecting this data is not easy. According to the report, only 7 percent of local authorities that have not monitored wastewater have the skills to start. The biggest obstacle to starting this process, according to the report, is the lack of internal staff. Rural authorities reported barriers to collection of wastewater data more often than non-rural areas.

It also appears that while public health officials agree that wastewater data is a powerful tool, many agencies based their pandemic response on other factors. Authorities monitoring the sewage rated the data as the least influential factors informing pandemic management.

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