COVID levels low in waste water
Report considered a key measure of disease prevalence
The amount of coronavirus detected in Eastern Massachusetts waste water has dropped to its lowest level in nearly two years, according to data from the Massachusetts Water Resources Authority.
Waste water data has emerged as an important way to keep tabs on the pandemic as fewer people test themselves for COVID-19 and even fewer results get reported to public health departments.
“There isn’t very much [coronavirus] transmission going on, and there has not been for a while,” said Bill Hanage, associate professor at the Harvard T. H Chan School of Public Health.
However, experts say it’s still too soon to simply forget about COVID-19.
Dr. Jacob Lemieux, an infectious disease specialist at Massachusetts General Hospital, said the downward trend was good news but that people are still dying of COVID, and many remain vulnerable to severe illness from the virus.
“We just need to hold these two realities in our minds at the same time,” Lemieux said.
The MWRA regularly tests waste water from Boston’s Deer Island Treatment Plant for traces of the virus that causes COVID-19. The seven-day average count of virus particles in waste water reached a low on June 23 and has ticked up only slightly since then.
The testing determines the number of coronavirus RNA copies per milliliter of waste water, as shed by people with and without symptoms. Areas to the south of Boston reached 91 copies per milliliter of waste water, and Boston and areas to the north reached 85 copies per milliliter. The numbers peaked during the height of the Omicron surge, when both areas climbed above 8,000 copies per milliliter of waste water. The last time both numbers fell below 100 was on July 20, 2021.
Matthew Fox, a professor of epidemiology and global health at the Boston
University School of Public Health, attributes the low numbers to Massachusetts having a highly vaccinated population.
Additionally, experts say the downward trend correlates with summertime. More people are outdoors, rather than clustered together inside, and “that puts us in a really good place,” said Fox.
But it is hard to say how long this period of relative calm will last.
“The virus continues to evolve, and the consequences of this evolution are somewhat unpredictable,” said Lemieux. Things could change in a matter of weeks or months, he said, depending on if and when a more concerning variant emerges, so he is taking the trends one day at a time.
Hanage believes there could be a COVID-19 uptick in the fall.
Seasonality is not a factor in COVID-19 transmission, Lemieux said, but in places like Boston where the academic calendar has large effects on the city’s population and migration patterns, it could lead to an increase in waste water numbers. With more folks gathering indoors due to the cold, schools back in session, and people’s immunity waning, more residents could be infected, said Hanage.
If there is an increase in COVID-19 cases during the fall, however, it will not be as steep as in prior years, many experts believe.
Dr. Peter Chai, an emergency medicine physician and medical toxicologist at Brigham and Women’s Hospital, is confident that by adhering to public health measures and continuing waste water surveillance, communities will be better protected and informed.
“One of the useful things about the waste water numbers is that we can be more confident that the low numbers are not hiding a lot of mild and uncounted cases,” Hanage said.
If anything were to change and there was a surge of a new variant, waste water tracking would also serve as a “great warning system,” Chai said.
“The biggest thing we need to do is care for those who are older, over 65, and those who are immunocompromised or are at high risk for other reasons,” Fox said.
However, everybody regardless of the risk group they’re in “should be fully vaccinated and up to date with their booster vaccinations,” said Lemieux. Other experts recommend that people continue masking, if needed.
Taking preventative measures “is a very personal decision,” Chai said, but these public health measures have proven to be highly effective.
Lemieux said that the question of how to respond to the circulation of COVID-19 remains a complex discussion on a societal level.
“I don’t think we’re at a place where we can forget about it. Certainly not those in high risk groups. And I don’t think that’s going to change for the foreseeable future,” he said.