COVID-19 XBB Strain Now 75% Of Cases In New England

MASSACHUSETTS — COVID-19 levels in some local wastewater have reached their highest point in about a year as the new XBB.1.5 variant of the omicron strain now accounts for 75 percent of all cases in the Northeast, according to data from the Massachusetts Water Resource Authority and the Centers for Disease Control.

The XBB.1.5 variant only made up around 7 percent of total cases across Massachusetts, New Hampshire, Connecticut, Rhode Island, Vermont, and Maine at the end of November. But as of Saturday, the variant now makes up more than 75 percent of total cases in the region.

Though cases and hospitalizations have also been on the rise in the region since mid-November, compared to the dramatic increase in virus levels in wastewater, these numbers are 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 this week.

"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."

"It's clear that the wastewater data show a dramatic uptick," Brigham and Women's Hospital's Dr. Daniel Kuritzkes added to NBC10 Boston. "What is contributing to this, though, is likely to be multifactorial. Undoubtedly, the ongoing evolution of the virus and the emergence of novel variants including XBB is a contributing factor, as are the recent gatherings, but it could also be a manifestation of the fact that, for many people who have not been boosted in a long time, that they are seeing the waning of some immunity."

The percentage of XBB.1.5 cases in the region is higher in New England than it is nationally, though the subvariant is also on the rise across the United States. At the end of the November, XBB.1.5 only accounted for only just over 1 percent of all infections nationwide. But the most recent data reveals that XBB.1.5 now accounts for 40.5 percent of total COVID-19 infections across the United States.

The XBB, BQ.1 and BQ.1.1 subvariants are currently the most antibody-resistant variants of COVID-19, according to a study published in the peer-reviewed journal Cell this month 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.

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.