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Coronavirus waste water numbers continue to creep up ahead of holidays

Deer Island waste water sewage treatment plant in Boston in the early morning.David L. Ryan/Globe Staff

Levels of coronavirus in Boston-area waste water have crept up ahead of the Christmas holiday, a reminder that three years into the pandemic, COVID-19 continues circulating in Massachusetts.

New Massachusetts Water Resources Authority data showed a seven-day average of 1,331 SARS-CoV-2 RNA copies per milliliter of waste water from the southern system as of Tuesday. The northern system sample, which includes waste water from the city of Boston, had 1,179 copies/ML on Tuesday.

The last time levels were that high was in late January of this year, when Eastern Massachusetts was recovering from the deadly Omicron surge.

Virus levels currently in the waste water are not much lower than they were at this time last year, when the surge was just beginning to take off. But experts told the Globe earlier this month that they were hopeful for a milder season, with higher immunity among the population helping to blunt the worst of last year’s surge.


Indeed, hospitalizations for COVID-19 were about 40 percent lower last week than the same period in 2021, according to state data.

Waste water samples are taken from the MWRA’s Deer Island sewage treatment plant. With more people opting for at-home COVID-19 tests that are not tracked by public health authorities, waste water monitoring has become an important tool in determining the amount of coronavirus circulating in the community.

The company that analyzes waste water, Cambridge’s BioBot Analytics, will be closed over Christmas and data collected Thursday through Tuesday will be delayed until late next week, according to a statement on the MWRA website.

Christina Prignano can be reached at christina.prignano@globe.com. Follow her @cprignano.