SOMERVILLE — Since the first cases of COVID-19 began trickling in last spring, the city’s approach to the virus has been a model of caution.
In April, Somerville was among the state’s first communities to offer free on-demand testing to residents, regardless of symptoms. It quickly rolled out a mask mandate, threatening stiff fines for violators. And over the course of the summer, as communities across the state began to reopen businesses, officials here played it safe, delaying the state’s third reopening phase by weeks.
Despite the measures, Somerville this week entered the high-risk, or “red,” category for coronavirus infections, joining the growing ranks of cities and towns across the state to cross the worrisome threshold and showing just how difficult the virus can be to mitigate, even for the most conscientious communities.
“We were doing so well,” lamented Joan O’Meara, a longtime Somerville resident, from a bustling Davis Square on Thursday, where people relaxed in cafes, got their hair cut, and worked out at the gym.
There are now 63 communities in Massachusetts in the higher-risk category, a designation given to communities that have recorded more than 8 cases per 100,000 residents in the past 14 days, according to public health data released Wednesday. When the state began issuing weekly reports on individual communities in mid-August, only four communities were in the red category.
Somerville registered at 8.2 on Wednesday. Boston also remained in the red, with a rate of 11.1, and the statewide average also reached the red, with the average daily rate at 8.7.
“I’m not surprised we’ve ticked into this,” said Somerville Mayor Joseph Curtatone, noting that many scientists have warned that cases will surge in the coming months. “Somerville has been careful and measured in its reopening. But we’re still a neighbor and abutter” to other cities in the area “and we know the virus knows no boundaries.”
Curtatone said city officials hadn’t identified any specific outbreak that has fueled the increase. Officials' best guess, he said, is that the virus is simply spreading in “familial settings."
He also noted that the rate in the densely settled city remains lower than the statewide figure and predicted that it would likely fluctuate in and out of the high-risk category.
Still, the city’s foray into troubling territory left some residents feeling uneasy.
Olive Obiapuna, a student at Fisher College who lives with her family in Somerville, said the latest numbers will likely push her to be even more careful about contracting and potentially spreading the virus — a task that could prove difficult since she relies on public transportation to get to and from school.
“I have to go to school,” she said. “I can’t not just go to school because of COVID. I’m just going to be careful, that’s all.”
Like others, Kendra Mitzman, 27, said she wasn’t surprised to hear that Somerville’s numbers had seen an uptick. A nurse at a large hospital, Mitzman said that views toward the virus may have shifted slightly, with many letting their guards down as they returned to familiar routines and activities more aligned with the Before Times.
“Part of that has to do with the school semester starting for kids and for college students,” she said. “There’s more people around, there’s more people spending time inside because it’s colder, and it makes perfect sense to me that it’s getting worse.”
Just across the city line, in Cambridge’s Porter Square, concerns about Somerville’s high-risk status seemed minimal. Alice Plane, who recently moved to Cambridge from Paris, said that while she’s being cautious, she doesn’t feel threatened by the nearby surge. Cambridge’s rate, at 3.3, is far lower than its neighbor’s.
“ ‘Worry’ is really the last word I would use,” she said.
Elsewhere across the state, however, high-risk cities were moving to make adjustments.
In Lowell, which fell into the red category for a third straight week with an average daily case rate of 16.4 — twice that of Somerville — public school officials announced a shift to full remote learning beginning next week. In Waltham, where the latest rate is 11.8, the health board has declared a public health emergency and is now requiring all residents and visitors to wear a mask at all times while in public.
Though Somerville has no immediate plans to take concrete actions, a city spokeswoman said officials would be monitoring the situation closely. Curtatone called for a more regional approach to fighting the pandemic, rather than the current town-by-town approach, which he likened to the arcade game “Whac-a-Mole.”
“It’s time to be bold and deliberate in doing what we need to do to knock down the resurgence of this pandemic,” he said. “We need to double down on efforts to contain the virus if we’re going to prevent the surge from overwhelming us.”
In Cambridge, which has shared its neighbor’s conservative approach to reopening, there was hope the rise in cases would serve as a wake-up call.
“What we do know is that this virus loves company,” said Claude Jacob, the city’s chief public health officer. “Should there be cause for concern? My short answer is it reminds us that we should remain vigilant and cautious.”
Martin Finucane of the Globe staff contributed to this story.