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Coronavirus levels in Boston-area waste water are falling, raising hopes of case declines

Coronavirus levels in Boston-area wastewater are falling, according to the latest data.Ryan Huddle/Globe staff

Waste water data collected from the Deer Island water treatment plant is showing a hopeful trend: Levels of coronavirus have plummeted in recent days after a massive spike.

The data raise the possibility that the wave of COVID-19 cases caused by the Omicron variant is about to crest. Experts were cautiously optimistic about the news.

“I did literally let out a hoot of excitement” upon seeing the new data, said William Hanage, an epidemiology professor at the Harvard T. H. Chan School of Public Health who is also a scientific adviser to Cambridge-based Biobot Analytics, the company that conducts the testing.


Hanage said people should expect COVID-19 case numbers to follow the waste water trend and peak “right around now” before falling. But he also cautioned that people should not get overconfident. “We don’t want to talk about the peak ever, because, heaven knows, we’ve had a lot peaks,” he said.

It’s still possible, he cautioned, that the numbers will plateau or even rise higher again.

Matthew Fox, a professor of epidemiology and global health at Boston University School of Public Health, said, “The waste water has certainly been very predictive so far. I’m really hopeful” that the case numbers are at their zenith.

“It seems like we’re following the pattern in the United Kingdom and South Africa … a massively fast rise and equally fast drop,” he said.

He said it’s possible cases could still stabilize or surge, but there’s usually a reason for that, such as the mixing of people during holidays, that can be identified. Right now, he said, “There’s nothing really on the horizon like that that we could pinpoint.”

The most recent readings from the Massachusetts Water Resources Authority’s plant found that the seven-day average of coronavirus levels in the waste water from the southern sample have fallen to 6,810 RNA copies/mL as of Monday. That’s down sharply from a high of 11,446 RNA copies/mL on Jan. 3.


Levels have fallen even lower in samples from the northern half of the system: The seven-day average was 5,091 RNA copies/mL as of Monday, down from a high of 8,644 on Jan. 5.

Coronavirus levels in the waste water are considered an early warning system for monitoring COVID-19 surges, as well as a complement to clinical testing. Biobot officials say they have found that the amount of virus detected in waste water is correlated with newly diagnosed coronavirus cases several days later.

The state has shattered records for new cases in recent days, and hospitalizations and deaths have been climbing. The staggering 60,986 confirmed cases reported in the three-day report on Monday was roughly the same as the total of all cases reported in May, June, July, and August.

Experts have been predicting the fast-moving Omicron wave could peak within about two weeks, with some saying it could happen as early as this week.

Still, they have noted that even if cases fall, hospitalizations and deaths would likely continue rising for weeks because those metrics usually lag cases.

“Although we may see an inversion point in the number of cases,” it will be followed by “increasing pressure on the health care system,” said Alessandro Vespignani, director of Northeastern’s Network Science Institute, who leads a team of infectious disease modelers.

Hanage said, “There’s a concern that it will continue to be a damaging strain on health care as a result of continued infections in the older age groups,” and he was particularly concerned about older people who haven’t yet gotten booster shots.


The SARS-CoV-2 virus, which causes COVID-19, is shed in the fecal matter of people who are infected. Experts say waste water tests can provides a true picture of infections at a given point in time, including people who are both symptomatic and asymptomatic, and those who got tested and those who didn’t. The wastewater infection numbers translate into case numbers only days later, after people are get tested, the tests are run, and the tests are officially reported.

Hanage said the MWRA data indicated that actual infections had peaked last week after people gathered during the holidays, saying a similar phenomenon had happened last year. “Past is prologue (sometimes),” he said in a tweet.

Dr. Ashish Jha, dean of the Brown University School of Public Health, cited the “big declines” in waste water numbers in saying that “the peak of this wave is coming into view.” At the same time, he cautioned that hospitals have “many tough weeks ahead.”

Joseph Allen, an associate professor at Harvard’s T.H. Chan School of Public Health and director of the Chan School’s Healthy Buildings program, tweeted that the plummeting numbers were “great news; hopeful this brings relief to Boston area healthcare system and healthcare workers — now a familiar pattern w/ Omicron.”

Dr. Paul Sax, clinical director of the Division of Infectious Diseases at Brigham and Women’s Hospital, also welcomed the new numbers, saying, “It’s encouraging, because waste water measurements are not subject to the problem of people having limited access to tests. They offer a realistic picture of how much virus is circulating in our community.”


“While the trend is favorable, people need to realize there is lots of COVID still out there – still higher than last winter,” he said in an e-mail.

He summed it all up in a tweet with a single word — “yahoo” — and a string of fingers-crossed emojis.

Christina Prignano can be reached at Follow her @cprignano. Martin Finucane can be reached at