Wastewater COVID-19 levels show promising decline

Wastewater tracking is a powerful tool used to get an early glimpse at future viral trends.

A view of the MWRA Deer Island Waste Water Treatment Plant. David L. Ryan/Boston Globe

Massachusetts residents bracing for a November surge of COVID-19 can breathe a sigh of relief — for now. 

The concentration of COVID-19 found in greater Boston’s wastewater is trending downwards, a welcome sign for those hoping to plan safe holiday gatherings later this month. Wastewater COVID-19 tracking is a powerful tool used to get an early glimpse at upcoming viral trends. 

The average amount of the virus found in wastewater samples has trended downward for the past couple weeks, according to data from The Massachusetts Water Resources Authority. The agency tracks samples from a northern region and a southern region of communities near Boston. The northern region stretches from Boston all the way up to Wilmington and Reading. The southern region includes parts of Newton and Brookline and towns as far south as Walpole and Stoughton. The southern region also stretches westward to encompass Framingham and Natick. 


The MWRA tracks the number of SARS-CoV-2 RNA copies per milliliter of water. The seven-day average in the southern region was 594 RNA copies/mL, as of Oct. 27. A week earlier, on Oct. 20, the average was 987 RNA copies/mL. The southern region average on Oct. 13 was 1094 RNA copies/mL. 

Similar trends are being observed in the northern region. The seven-day average for that area was 340 RNA copies/mL on Oct. 27. A week prior, the average was 877 RNA copies/mL. The northern region average on Oct. 13 was 673 RNA copies/mL. 

This data is collected through testing at the MWRA Deer Island Treatment Plant. Samples are taken between three and seven times a week. They are analyzed by wastewater epidemiology company Biobot Analytics. 

Wastewater tracking is important because people infected with SARS-CoV-2, the virus that causes COVID-19, shed that virus into wastewater when they use the bathroom. This happens regardless of whether or not they are exhibiting symptoms, according to the NIH. Thus, wastewater sampling can be used as an early warning for heightened levels of the virus in a particular community. 

Although wastewater tracking is not as robust throughout Massachusetts as it is in the great Boston area, the data collected over the past six weeks shows downward trends in nearly every Massachusetts county, according to Biobot.


The company also breaks down wastewater data by region. The virus concentration in the northeast of the country has dipped from earlier October, but still remains higher than the national average and other regions. The northeast was found to have an average of 786 RNA copies/mL on Oct. 26, down from 1,248 RNA copies/mL on Oct. 12. 

The national average on Oct. 26 was 518 RNA copies/mL, according to Biobot. There was a major peak of copies detected in mid-July, but nothing compared to the highest recorded national average, which was 4,780 RNA copies/mL on Dec. 29, 2021.   

To make sure people remain safe during the upcoming holiday season, officials are urging the public to get their updated booster vaccines. Information on the vaccines, including how to find a location to receive a free shot, is available online at


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