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Levels of coronavirus in Eastern Mass. waste water still rising

Waste water coming in to the Deer Island treatment plant on Boston Harbor is tested for traces of the virus that causes COVID-19.David L. Ryan/Globe Staff

The levels of coronavirus detected in Eastern Massachusetts waste water continued to climb in recent days, as concerns persist that the arrival of the Omicron subvariant BA.2 could cause an increase in COVID-19 cases.

The levels fell precipitously from heights reached early this year as the Omicron wave peaked, then bottomed out around the beginning of March. They have been rising gradually since, although they are still a small fraction of their peak, according to data from the Massachusetts Water Resources Authority.

Waste water from 43 communities, including Boston, converges at the MWRA’s Deer Island plant in 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. Scientists say that tracking the levels can serve as advance warning several days ahead of case increases.

For the southern MWRA region, the seven-day average was 303 copies/mL as of Monday. That’s 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.

In the northern region, the seven-day average was 313 RNA copies/mL as of Monday, up from 101 on March 9. The levels peaked at 8,644 on Jan. 5.

COVID-19 cases are also on the rise but remain far below the last peak. The infectious BA.2 variant has caused a surge of cases in Europe so officials are keeping a close eye on it here.

Material from Globe wire services was used in this report.

Martin Finucane can be reached at martin.finucane@globe.com.