Levels of coronavirus detected in Boston-area waste water have reached new highs, with seven-day averages that shatter previous record-breaking levels.

On Dec. 29, the seven-day average of virus traces in the waste water in the southern sample of the Massachusetts Water Resources Authority’s territory was 8,164 RNA copies/mL. That’s up from 2,574 RNA copies/mL on Dec. 23, meaning the average has more than tripled in the last six days.

Waste-water testing serves as an early warning sign for a 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 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 most recent tests found that the seven-day averages of virus traces in the waste water have risen extremely fast over the last three weeks.

The samples also show how fast the virus is transmitting: on Dec. 13, the seven-day average in the southern sample was 1,363 copies/mL. This means that the seven-day average has increased nearly sixfold in a little more than two weeks.

In the northern sample, which includes the Boston area, the seven-day average rose from 2,411 RNA copies/mL on Dec. 23 to 6,322 RNA copies/mL on Dec. 29, meaning that the average has almost tripled in the last six 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 had a sharp increase in COVID-19 cases. On Dec. 30, the state reported 21,137 new confirmed coronavirus cases, setting another new daily record.

The US also shattered its own record for new daily coronavirus cases on Dec. 30, reporting more than 580,000 cases.

The breakdown of which Massachusetts towns are included in the northern and southern waste water systems can be found here.

Martin Finucane of the Globe staff contributed to this report.

Maria Elena Little Endara can be reached at [email protected].

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