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More cases ahead? Coronavirus in Boston-area waste water is on the rise again

Tests are conducted at the MWRA's Deer Island treatment plant.Lane Turner/Globe Staff

In worrisome news for residents on edge about the supercontagious Delta variant, the amount of coronavirus in Boston area wastewater is on the rise again, a possible signal of case increases ahead.

Levels of coronavirus in the wastewater coming from the northern section of the Massachusetts Water Resources Authority, which includes Boston, are now similar to those in late January. Levels from the southern section have reached levels similar to April. The numbers reflect tests taken as recently as Friday.

The pilot program tests for SARS-CoV-2 RNA copies per milliliter of wastewater at the MWRA’s Deer Island treatment plant. Officials think the tests can serve as an early warning system for surges in cases. Cambridge-based Biobot Analytics, which conducts the tests, 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.


Dr. Paul Sax, clinical director of the Division of Infectious Diseases at Brigham and Women’s Hospital, said Sunday in a tweet about the MWRA data, “Not liking this trajectory (which often predicts what’s coming in weeks ahead) one bit. But better to be prepared than live in ignorance.”

The Delta variant is linked to rising case, hospitalization, and death counts nationwide, especially in areas with higher community spread and lower vaccination rates, according to the Centers for Disease Control and Prevention.

Massachusetts is a national leader in vaccinations that are highly effective against severe disease and death. Officials and experts are hoping that the vaccinations will blunt the variant’s impact here, with higher case counts not resulting in the same amount of hospitalizations and deaths as in previous phases of the pandemic.

“If you get people vaccinated, there will be people who will test positive but they’re not going to get as sick as they would if they weren’t vaccinated,” Governor Charlie Baker said last week.


Baker said Monday that the state is doing far better in terms of coronavirus metrics than many other states and lauded Massachusetts residents for getting their shots.

“The fact that so many people in Massachusetts have been vaccinated — and that is a real tribute to the enthusiasm that the people of this Commonwealth showed to getting vaccinated — has put us in a dramatically different place than many other states across this country,” he said. “I hope and pray that many other states move as aggressively as the people in Massachusetts have moved to get vaccinated. Vaccinations are the pathway out of this pandemic. Period.”

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