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No relief yet: Levels of coronavirus in Mass. waste water continue to rise

Waste water is tested for traces of the coronavirus at the Deer Island treatment plant on Boston Harbor.David L. Ryan/Globe Staff

There’s no sign of a letup yet. The levels of coronavirus detected in Eastern Massachusetts waste water continued to climb last week, suggesting more COVID-19 case increases are ahead, according to data from the Massachusetts Water Resources Authority.

Officials say waste water virus data can be an important early warning signal, detecting COVID-19 infections before people get tested and the tests are officially reported. As more people are using at-home COVID-19 testing kits, whose results are usually not reported to state public health officials, waste water tests have become a key indicator of the virus’s prevalence.

The waste water levels have now rebounded to where they were in late January.


The increases come as Massachusetts COVID-19 cases and hospitalizations have also been gradually rising for weeks, and the CDC has designated 11 of the state’s 14 counties as having high levels of the virus. The CDC recommends that when virus levels are high, people should mask in indoor public spaces.

If you think there’s a lot of virus circulating out there right now, “you’re absolutely right,” Dr. Paul Sax, clinical director for the Division of Infectious Diseases at Brigham and Women’s Hospital, said Sunday in a tweet, citing both the waste water and case data.

He also pointed out the case numbers in Massachusetts now are much higher than they were at this time last year.

Experts have raised concerns that the arrival of the Omicron subvariants BA.2 and now BA.2.12.1, could breathe new life into the pandemic. Models offer hope that the current Massachusetts wave could crest in the coming weeks. Experts say that would happen for a variety of reasons, including the immune protection people have gotten from vaccinations and previous infections.

Dr. Jacob Lemieux, co-leader of the viral variants program at the Harvard Medical School-led Massachusetts Consortium on Pathogen Readiness, said last week in an interview posted on the medical school website that the state’s waste water data suggested “we’re going to see this continued increase in cases for at least another week or two, and probably longer.” He also said the amount hospitalizations that have gone up is “really concerning.”


“We don’t fully understand what’s driving this, but novel variants seem to be a big part of it,” he said.

He said that “in New England, we’re now dealing with a nearly complete BA.2.12.1 epidemic.”

Early this year, the Eastern Massachusetts waste water levels dropped precipitously from their Omicron peak. They bottomed out in early March, then began rising again. The rise was interrupted by a dip last month, but the levels have now more than bounced back.

The numbers remain at much lower levels than they were when the Omicron surge hit the region during the winter. The number of confirmed reported daily COVID-19 deaths has so far not taken off, staying in the single digits.

Waste water from 43 communities, including Boston, converges at the MWRA’s Deer Island plant on Boston Harbor for treatment before being piped miles into the ocean. The water is tested for traces of the deadly virus. The MWRA reports numbers for both the southern and northern regions of its system. The testing determines the number of SARS-CoV-2 RNA copies per milliliter of waste water.

In the northern MWRA region, the seven-day average was 1,035 RNA copies/mL as of Friday. That’s up from a low of 101 on March 9. The levels peaked at 8,644 on Jan. 5.


In the southern region, the seven-day average was 1,113 RNA copies/mL on Friday, up from a low of 92 copies/mL on March 1. But it’s a far cry from the high of 11,446 RNA copies/mL reached on Jan. 3.

Martin Finucane can be reached at martin.finucane@globe.com. Christina Prignano can be reached at christina.prignano@globe.com. Follow her on Twitter @cprignano.