Two Harvard public health experts said a small spike in coronavirus detected in wastewater tested by the Massachusetts Water Resources Authority is yet another warning sign that the state must be more vigilant to slow the virus’s spread.
The professors from the Harvard T.H. Chan School of Public Health urge Gov. Charlie Baker to further curtail the state’s reopening plans, particularly as schools and colleges plan to return to in-person learning in the fall.
The data, gathered and analyzed through a pilot study run by the MWRA and Somerville-based Biobot Analytics Inc., showed small increases in the amount of the virus in sewage gathered north and south of the Deer Island treatment plant.
An update released Wednesday by the MWRA showed a slight upward trend beginning in late July and extending into early August, reaching a point roughly double that of the lowest virus count in late June.
That information, combined with increases in positive tests and other closely watched metrics, suggests that “we should expect to see a lot more cases in the days and weeks ahead in Massachusetts,” said Dr. Ashish Jha, head of the Harvard Global Health Institute.
“We’re seeing a rapid rise in cases, and the governor and the Legislature have two choices,” he said. “They can act now, and stem this tide, or they can wait a couple of weeks, and then they’re going to have to act much more aggressively. … I believe at this point that it is important for the governor to go back to Phase 2.”
Most of Massachusetts entered Phase 3 on July 6, with limits on gatherings expanding from 10 people to up to 100 for outdoor gatherings and 25 for indoor events, and with gyms, movie theaters, casinos, museums, and other public facilities allowed to reopen.
In a return to Phase 2, many businesses would be forced to close again, and outdoor gatherings — already reduced Friday from a limit of 100 people to 50 — could again be limited to just 10 people, as could indoor gatherings.
Jha said if the state doesn’t return to tighter restrictions, cases will likely continue to increase as Labor Day approaches, making it increasingly dangerous for schools to reopen with classes held on campus.
“If the cases are still going up on Labor Day, schools are going to be very hesitant to open, and rightfully so,” he said.
Asked for comment Friday night, a spokeswoman for Baker pointed to the state’s new restrictions, including a reduction on the size of outdoor gatherings from 100 to 50 people, and to the governor’s comments during his daily briefing Friday.
Baker told a reporter who asked about returning to Phase 2 that contact tracing had shown that the largest source of new cases was large, outdoor social gatherings.
“Now if you think about a party, take a Fourth of July party or even a birthday party. 40 or 50 people in somebody’s backyard,” Baker said, according to a transcript. “Moms and dads, the kids, all the rest. Nobody wearing a face mask, nobody socially distancing. One or two people there who are asymptomatic or pre-symptomatic. Hugs, handshakes, high fives, dancing, who knows. A whole bunch of people walk away from there, little ticking clocks that are going go off at some point.”
William Hanage, an associate professor of epidemiology at the Chan School , said Baker’s explanation demonstrates that there are limits to the benefits of holding events outdoors — though “outside is definitely safer than inside.”
“I dread to think what would have happened if we’d had gatherings of 50 people indoors, rather than in a backyard,” Hanage said. “However, it is not completely safe. And the same thing with wearing a mask. People should not think that wearing a mask makes them completely safe, or any of the people around them completely safe. It’s all about reduction of risk.”
Hanage said the wastewater data, along with the recent rise in the number of cases, demonstrates how easily the virus can be spread and provides potential guidance for the future.
“It tells us something really crucial about the way the virus transmits, which is it doesn’t take a huge amount for it to be able to start ticking up again,” he said, adding later, “This strongly suggests there are elements of the last part of the phased reopening plan which are not compatible with keeping the virus under wraps.”