Earlier this month, the City of Boston began sampling waste water from 11 manholes in as many neighborhoods across the city. The goal is to get a more localized look at how the coronavirus is spreading.
What emerged was a picture of glaring, though unsurprising, disparities.
According to the most recent report, released Monday, Roxbury had the highest coronavirus levels in the city — more than three times those of Roslindale/West Roxbury and Charlestown, which had the lowest levels. Allston/Brighton, Mattapan, and Dorchester also had above-average counts.
Public health experts said there were many reasons for the differences. “The most likely factors include vaccination and booster rates, access to care, systemic health inequities, the number of residents working in jobs that put them in close proximity to others, and the number of residents that live in crowded conditions,” said Dr. Kathryn Hall, the Boston Public Health Commission’s deputy director.
The commission plans to use these samples to create more targeted interventions in neighborhoods experiencing higher levels of COVID, including deploying masks and sponsoring vaccinations, in addition to the free vaccination sites it continues to operate in Roxbury and other neighborhoods disproportionately affected by the pandemic, according to Hall.
“This has been the story for much of the pandemic and it’s not surprising that it continues this way,” said Dr. Jonathan Levy, chair of Boston University’s Department of Environmental Health.
People’s exposure levels can vary depending on how many people they live with, whether they are able to work remotely, and their ability to isolate during periods of high community spread, among other factors, Levy said.
Waste water has emerged as a reliable indicator of COVID prevalence, now that more people use rapid, at-home COVID tests that don’t get reported in official case counts. The Boston data, which Hall said will be gathered twice a week and posted online, come from manholes in Brighton, Back Bay, Charlestown, Dorchester, East Boston, Hyde Park, Jamaica Plain, Mattapan, Roslindale, Roxbury, and South Boston.
Overall, Boston’s coronavirus levels were higher than average for Eastern Massachusetts. Areas to the south, stretching from Boston to Stoughton, had a count of 892 RNA copies per milliliter, while areas to the north, stretching from Boston to Wilmington, averaged 1,262. Boston’s average was 1,677 RNA copies per milliliter.
“We know, based on what level of waste water we have, roughly how many cases there are and how many days before we see it hit the hospitals,” Hall said. “It’s just an amazing tool to have.”
Compared with a set of data that Boston released three weeks ago, COVID-19 levels are on a downward trend in every Boston neighborhood.
The newest report, based on data collected through Jan. 18, shows a 50 percent decrease in COVID levels in Boston over the past two weeks.
The data also found significant reductions in neighborhoods such as Roxbury and Allston/Brighton.
Roxbury, which had 6,456 RNA copies/mL as of Jan. 4, dropped to 2,642 RNA copies/mL. Similarly, Allston/Brighton’s levels dropped from 4,438 RNA copies/mL to 2,516 RNA copies/mL
Overall, Hall said she’s “cautiously optimistic” about the numbers and that, in her opinion, people seem to be taking precautions seriously.
“I see people wearing masks on the street and asking to get vaccinated and boosted,” she said. “And so many people got COVID in that peak, which is going to give us a little bit of protection for a while.”