A COVID-19 subvariant estimated by health officials to be even more contagious than the first descendant of the potently infectious omicron strain now accounts for 40% of all virus circulating in New England, according to new CDC data released Tuesday.
The prevalence of BA.2. 12.1, which health officials say appears to be up to 27% more contagious than BA.2, rose from 28% of all cases here to 40% in just one week.
That largely mirrors what's been seen in New York of late, where a surge in BA.2. 12.1 cases -- it now accounts for two-thirds of cases in the Tri-State area -- has led to what they're calling the fifth wave of the coronavirus pandemic. New York City raised its alert level to "medium" last week, and Health Commissioner Dr. Ashwin Vasan said last week that all options could be on the table if things continue to get worse, including the return of a mask mandate.
Get Boston local news, weather forecasts, lifestyle and entertainment stories to your inbox. Sign up for NBC Boston’s newsletters.
While no scientific evidence to date links BA.2. 12.1 to more severe COVID-linked illness or reduced vaccine efficacy at this point, the heightened transmissibility appears clear.
Get the latest news on COVID-19 delivered to you. Click here to sign up for our weekly coronavirus newsletter.
Are COVID numbers in Massachusetts rising?
And though things aren't quite as bad here in Massachusetts right now, things do appear to be trending in the wrong direction.
The community test positivity rate in Boston -- which excludes colleges -- is now over 10%, as of last Thursday, and continued climbing on Friday and Saturday. And several area schools, including Arlington, Belmont and Cambridge, are once again urging students and staff to wear masks as cases continue to climb.
Massachusetts' COVID metrics, tracked on the Department of Public Health's interactive coronavirus dashboard, have declined since the omicron surge, but case counts are starting to creep up once again.
Massachusetts health officials reported 8,625 new COVID-19 cases over the weekend. The state's seven-day average positivity rate increased to 6.77% Monday, compared to 6.63% on Friday.
"I think that we are all concerned," Dr. Bisola Ojikutu, executive director for the Boston Public Health Commission, said Monday. "There is no reason for panic, however, we are concerned and we are following this data very closely."
What does the latest COVID wastewater data say?
COVID levels in wastewater, as reported by the Massachusetts Water Resources Authority's tracking system were slightly down at the start of last week in the Boston area, though it wasn't enough to convince top Boston doctors that we were clear from the spring surge. As of samples through Wednesday, those levels were on the rise again, so the trend has not been consistent.
It's important to note, however, that the levels of virus seen in the wastewater remain nowhere near where they were during the peak of the omicron surge.
"It is really lower than the winter omicron peak in January, and in general, we are noting that severity of illness is also lower, so this is good news," Ojikutu said. "But we do have a very high level of cases."
"We are tired, I know, of this virus, and want to be moving on, but the reality is that cases are still in our community. I think everybody knows someone right now that has recently tested positive," Boston Mayor Michelle Wu added. "We are monitoring those numbers very carefully, have that wastewater data that's really important, and making sure that we can be responsive."
Will New England see another COVID wave like New York?
Top Boston doctors interviewed this week said it's still too soon to say if we'll experience a fifth wave similar to what New York is now going through.
"Well, you know, as I think we've talked about in the past, what we're seeing is that instead of completely new variants emerging out of nowhere and then taking over, omicron seems to be here to stay," Brigham and Women's Hospital's Chief of Infectious Disease Dr. Daniel Kuritzkes said. "And omicron is fine tuning its capacity to infect and to evade the immune system. So we're not seeing major changes in the virus but tinkering around the edges to be able to find the right path to be able to infect even in the presence of have some immunity whether it's from vaccination or from from previous infection."
"So I would predict that we'll see a bump and not a massive spike. But that's an optimistic hope, more than a scientifically based prediction, but the rationale for predicting that is that I think that there is probably enough protection among people who have been infected with earlier versions omicron."
"It's hard to predict how a particular sublineage will behave, you know. Time will tell in terms of disease severity and immune evasion, so we just have to to wait," said Boston Medical Center's Dr. Sabrina Assoumou.