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Another good sign: Traces of coronavirus in MWRA waste water are on the decline again

Waste water coming into the Deer Island treatment plant is tested for traces of coronavirus every day.
Waste water coming into the Deer Island treatment plant is tested for traces of coronavirus every day.Lane Turner/Globe Staff

In another encouraging sign, the amount of coronavirus is on the decline in waste water at the MWRA’s Deer Island treatment plant.

The water is being tested for SARS COV 2 copies per milliliter as part of a pilot project that is intended to serve as an early warning system for future surges in the pandemic.

The seven-day average of virus traces in the waste water declined for seven of the last eight days for the southern section of the MWRA system. For the northern section of the system, which includes Boston, the levels have dropped for nine days in a row. The data reflects tests taken as recently as last Thursday.


The levels have not yet dropped to the levels of last summer, however.

The amount of virus detected soared during the state’s second surge early this year, then dropped precipitously. The levels bumped up slightly around the beginning of March, adding to the suspense about whether the state would see a third surge.

Cambridge-based Biobot Analytics, which conducts the testing, 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.

Biobot says its tests detect the coronavirus, no matter what variant. But it has also developed the capability to specifically detect the B.1.1.7 variant from the United Kingdom, and it has been found in the waste water consistently since testing for it began.

Meanwhile, Dr. Ashish Jha, dean of the Brown University of School of Public Health, on Monday predicted a “good summer” ahead due to the pace of the US vaccination campaign.

He noted in a stream of tweets that US case numbers are falling and said, “This time, I think it’ll stick Why? Vaccines!”

“While some states may still struggle, we should be on a better path,” he said.


He said vaccines were “now plentiful” but, as expected, vaccinations have started dropping.

He said access was “still a challenge for many,” while others are “unsure.”

“We need to better address their concerns But as we make progress, infections will fall further,” he said. “And that should lead to a good summer.”

Ryan Huddle of the Globe staff contributed to this report.

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