COVID-19 Wastewater Levels Vary In MA, But Headed Down In Places

After a considerable uptick in COVID-19 levels in Massachusetts wastewater at the end of December and beginning of January, trends in some parts of the state seem to be slowly back on their way down, according to recent data from the Massachusetts Department of Public Health.

COVID-19 levels in Boston-area wastewater reached their highest point in about a year in early January as data showed that the XBB.1.5 variant of the omicron strain, which once made up only a small percentage of all cases in the Northeast, had come to account for 75 percent of all cases in the region. But as of Tuesday, wastewater COVID-19 levels in the Boston area had begun to trend downward, with concentration levels falling by several hundred thousand copies per liter in both the northern and southern metropolitan areas between Jan. 5 and Jan. 10.

Data shows that in Worcester, wastewater COVID-19 levels have stayed relatively consistent over the past three months, with levels increasing at a much lower rate than that of the Boston area at the end of December and in early January.

Meanwhile, data for levels on the North Shore have not been updated since Jan. 4, though the area saw the highest increase of COVID-19 wastewater levels among the three areas at the end of December and beginning of January — roughly three and a half times that of the Boston area around the same time period.

Though cases and hospitalizations also rose at the end of December, compared to the sharp increase in virus levels in wastewater, these numbers were not as dramatic, data shows.

This disparity might be due to differences in viral loads — or the amount of virus in a person's blood — that are seen in across the variants and subvariants, Tufts Medical Center's Dr. Shira Doron told NBC10 Boston in early January.

"One of the reasons that a subvariant might take off is higher infectiousness due to being associated with a higher viral load," Doron told the outlet. "And if that's the case, then a rise in the amount of virus in the wastewater could sometimes not be directly correlated with any number of cases."

The XBB, BQ.1 and BQ.1.1 Omicron subvariants are currently the most antibody-resistant variants of COVID-19, according to a study published in the peer-reviewed journal Cell in December by scientists affiliated with Columbia University and the University of Michigan. This means that even those with the most recent booster vaccine meant to protect against the Omicron variant as a whole are still experiencing breakthrough infections.

According to the CDC, the Omicron variant spreads more easily than the original SARS-CoV-2 virus and the Delta variant. However, symptoms are generally milder, and unlike the Delta variation, the Omicron strain often affects the upper-respiratory tract rather than the lungs, Dr. Karine Markosyan, a physician at the St. Gregory the Illuminator Medical Center, told Unicef in March 2022.

Yale Medicine emphasizes that some people infected with Omicron still develop severe disease and have to go to the hospital, and some die. Still, the CDC says that being up to date on COVID-19 vaccination provides strong protection against severe disease, hospitalization, and death in all age groups.