Coronavirus detected in Boston-area waste water soars to record levels

MWRA's Deer Island sewage treatment plant is seen from Spectacle Island in Boston Harbor.Lane Turner/Globe Staff

The detection of coronavirus in Boston-area waste water has reached record-breaking levels, with the most recent seven-day average soaring past previous record highs set earlier this month.

On Dec. 23, the seven-day average of virus traces in the waste water in the southern sample of the Massachusetts Water Resources Authority’s territory was 2,574 RNA copies/mL. That’s up from 1,136 copies/mL on Dec. 1, meaning the average has increased by 127 percent in the last three weeks.

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

The increase in the waste-water levels continues a trend that began around late November, but the tests found that the seven-day averages of virus traces in the waste water have risen incredibly fast over the last three weeks.

In the northern sample, which includes the Boston area, the seven-day average rose from 1,328 RNA copies/mL on Dec. 16 to 2,411 copies on Dec. 23, meaning that the average has almost doubled in the last seven days.

Levels of coronavirus in waste water coming from the northern and southern samples of the MWRA’s territory have both risen substantially, well beyond levels seen at the height of the deadly winter surge in mid-January 2021, when cases rose to 5,000-plus per day.

In the past several weeks, Massachusetts has seen a spike in COVID-19 cases. On Dec. 24, the state reported 10,040 new confirmed cases, the highest total reported in a single day since the start of the pandemic. It was the third day in a row that the state reported a new single-day high.

Earlier last week, Governor Charlie Baker deployed the National Guard to help hospitals in Massachusetts struggling with staff shortages and ordered them to cancel nonessential surgeries to accommodate a tide of patients sick with COVID and other serious illnesses.

Martin Finucane of the Globe staff contributed to this report.