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Coronavirus levels in Boston-area waste water have risen dramatically in recent days

MWRA's Deer Island Sewage Treatment Plant is seen from Spectacle Island in Boston Harbor.Lane Turner/Globe Staff

Coronavirus readings in Boston-area wastewater have seen a dramatic rise in recent days, reaching levels not seen since the height of the January surge.

The increase in the wastewater levels continues a trend that began around mid-November, but the tests found that the seven-day averages of virus traces in the wastewater have risen particularly fast over the last week or so.

Levels of coronavirus in wastewater coming from the northern and southern samples of the Massachusetts Water Resources Authority’s territory have both risen substantially, returning to levels last seen in mid-January.

On Dec. 3, the seven-day average of virus traces in the wastewater in the southern sample was 1,391 RNA copies/mL. A week prior, the seven-day average was 580 RNA copies/mL, meaning that the average has more than doubled in the last seven days.

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In the northern sample, which includes the Boston area, the seven-day average rose from 630 RNA copies/mL on Nov. 26 to 1,077 RNA copies/mL on Dec. 3.

Wastewater testing serves as something of an early warning sign for a coming COVID-19 surge. Cambridge-based Biobot Analytics, which tests the wastewater coming into MWRA’s Deer Island treatment plant, says it has found that the amount of virus in the waste water is correlated with newly diagnosed coronavirus cases four to 10 days later.

In the past several weeks, COVID cases in Massachusetts have gone up more than 150 percent and hospitalizations have nearly doubled. The uptick in cases is a reflection of a new wave taking hold across the country as colder weather shifts people indoors and vaccine efficacy wanes. Public health officials in Massachusetts are encouraging residents to remain cautious and get vaccinated.

Over the weekend, officials detected Massachusetts’ first case of the Omicron variant in a fully vaccinated Middlesex woman.

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Martin Finucane of the Globe staff contributed to this report.


Maria Elena Little Endara can be reached at mariaelena.littleendara@globe.com.