scorecardresearch Skip to main content

Boston area wastewater numbers continue downward trend

COVID hospitalizations, too, are at their lowest levels in a year.

Deer Island Wastewater sewage treatment plant in Boston in the early morning.David L. Ryan/Globe Staff

Coronavirus levels detected in Boston area wastewater have dropped to their lowest numbers in over a year, according to data from the Massachusetts Water Resources Authority.

The levels are an important indicator of the prevalence of COVID-19 infections at a time when fewer people are testing for the virus or reporting results to the state.

“We haven’t had a number this low in 13 months,” said Dr. Shira Doron, Chief Infection Control Officer for Tufts Medicine health system and Hospital Epidemiologist at Tufts Medical Center. “These are great numbers to have.”

Hospitalizations are also at their lowest levels since last April.


Through big waves of “immune-evasive variants,” such as the Omicron variants, communities have built up immunity over time, said Doron. That means we’re unlikely to see another surge of hospitalizations and deaths like we did in the earlier years of the pandemic, even though rates will likely fluctuate a bit, as they do with other viruses, like the flu.

“That’s not to say that people who are immunocompromised or high risk or simply fearful should not still take [reasonable] precautions,” she said. “But, from the standpoint of whether we call it a public health emergency or a pandemic, I think those things are over.”

Wastewater testing measures the number of SARS-CoV-2 RNA copies per milliliter of water. The latest data, released Tuesday, showed a seven-day average of 162 copies/mL from the southern system, which stretches from Newton, Brookline, and Framingham to Stoughton, and 159 copies/ML in the northern system, which stretches from Boston to Wilmington. These numbers are a sharp reduction from the same date last year, when recorded levels were 666 copies/ML in the southern system and 673 copies/ML in the northern system.

COVID-related hospitalizations in the state have also been trending downward following a spike in January. According to state data, the seven-day average of confirmed COVID-19 hospitalizations Tuesday was 270.3 patients, the lowest it has been in a year.


Doron said hospitals are now seeing waves of patients who put off getting regular medical services out of fear of the virus or because services were less accessible during the pandemic. But, cases of the virus itself are no longer taking up significant health care resources, she said.

Moving forward, people can take an individualized approach to masking and other precautions, based on their comfort and risk levels, said Dr. Sabrina Assoumou, an infectious disease physician at Boston Medical Center and assistant professor of infectious diseases at the Boston University Chobanian & Avedisian School of Medicine.

People who are at higher risk for complications and those who are unvaccinated or undervaccinated should still consider masking when indoors or in crowded places, she said. But, overall, people can be reasonably reassured that “we’re in a much better place than we were before.”

“We’re dealing with a population that has now seen this virus and are better able to withstand fluctuations. Last winter was a bump as opposed to a surge,” she said. “Most people have built a level of immunity through vaccination, infection or both.”

Both experts agree wastewater tracking has “proven time and again” that it is the most dependable way to keep track of the virus. Doron said she no longer pays much attention to case rates, given that most people no longer test regularly.


Biobot Analytics, the company that offers the wastewater monitoring, announced Wednesday it will expand its program to monitor norovirus beginning in May. A highly contagious virus that causes diarrhea and nausea, norovirus is the leading cause of foodborne illness in the country, according to the Centers for Disease Control and Prevention.

“Norovirus rates continue to be at a yearly high across the country. Wastewater monitoring provides equitable and inclusive data that can help public health officials prepare and respond more effectively to outbreaks,” said Mariana Matus, CEO of Biobot Analytics, in a statement.

Zeina Mohammed can be reached at Follow her @_ZeinaMohammed.