NEW YORK — New York officials have embraced a new strategy to quash coronavirus spikes — shutting down schools and businesses with almost surgical precision, using block-by-block infection data while also boosting testing and contact tracing in those communities.

The idea is to stamp out virus sparks quickly, before adjacent areas catch flame, while avoiding the devastation of citywide lockdowns.

The unique effort, supported by a massive state and city testing apparatus, has been largely successful so far, earning the admiration of epidemiologists. But neither state nor city officials are taking a victory lap as they watch cases surge to their highest-ever levels in sister cities throughout the United States and Europe — and with painful memories of the spring outbreak when virus deaths exceeded 700 per day.

“We’re all heartened at the fact that this is working,” said Jackie Bray, deputy executive director of NYC Test & Trace Corps, an initiative the city launched in June that employs 4,000 tracers with a budget of about $1 billion in city and federal funds. “We’re clear-eyed at how hard this is going to be to sustain through the fall and the winter.”

The policy has allowed the city to avoid returning to blanket closures, unlike the European cities that also suffered immensely in the pandemic’s first wave. France placed a 9 p.m. curfew in nine cities, including Paris. Italy tightened restrictions across its restaurants and bars.

A growing number of states and cities in the United States have also added restrictions on public activity. Massachusetts on Monday shortened hours for some businesses to encourage people to stay home at night. New York continues some statewide restrictions as well, such as requiring masks on public transit. But its data-based, hyperlocal approach differs from what others have implemented.

The policy had its origins in October when the state released a color-coded map — yellow, orange and red zones, least to most severe — which appeared as angry bull’s eyes around clusters in Queens and Brooklyn, both parts of New York City, as well as suburban Rockland and Orange counties.

The map is built from the results of the nearly a million coronavirus tests New York has conducted per week, or about 0.6 percent of the state population daily, as of late October. The home address of every person with a positive test result is funneled into a health department database. Such data determines whether areas are designated red, orange or yellow zones.

“We identify the micro-cluster, that’s called a red zone. We then put a buffer around it, that’s called an orange zone, we then put a buffer around the orange zone which is a yellow zone,” New York Gov. Andrew M. Cuomo (D) said at a news conference on Oct. 21, likening the spread of the virus to ripples created by a pebble dropped in a pond. “These areas are so small that people walk to a store, people walk to a restaurant and you see the viral expansion will be a series of concentric circles.”

The NYC Test & Trace Corps sends city workers equipped with rapid diagnostic tests into the zones and, alongside them, contact tracers. Those disease detectives conduct in-person interviews immediately after people receive results detecting coronavirus infections.

Those who test positive are asked to isolate at home for at least 10 days. If they are unable to do that — because they share their home with others and are unable to remain in a separate room, for instance — the city provides a hotel room free, said Ted Long, a physician and the executive director of the Test & Trace Corps. More than 2,500 people have isolated in hotels.

Medicine, food and other necessities can be delivered, he said, and the city mails masks and snacks each day to about 500 people in isolation at their homes.

While less draconian than the spring’s citywide lockdown, the policy is unpopular among those who live and work in the targeted communities. “Small businesses feel that they are being unfairly punished,” said Randy Peers, chief executive and president of the Brooklyn Chamber of Commerce. The state should be focused on individuals who violated coronavirus mandates, not the thousands of compliant businesses “caught up in this crossfire,” he said.

Many business owners had been relieved in July when officials lifted many coronavirus restrictions on the city.

Throughout the summer, health officials were able to extinguish small clusters centered in Brooklyn and Bronx neighborhoods. “When the Department of Health said: ‘We’ve got a signal, we’ve got an uptick,’ there were mobile testing units to send in,” Bray said. Vans and tents for testing, which the city has begun weatherproofing for winter, were set up at parks and on sidewalks.

An alarming increase

Things began to slide after an ultra-Orthodox wedding in mid-August seeded the virus in the densely populated Borough Park neighborhood of Brooklyn.

After city officials saw a small uptick in cases, the NYC Test & Trace Corps deployed its mobile units and began robocalling residents. It translated informational fliers into Yiddish to communicate with the Hasidic Jewish community there. Public health experts spoke with community leaders and writers at local papers.

But unlike earlier in the summer, the numbers continued to rise. By the first week of September, city officials identified four potential hot zones in Brooklyn and Queens.

“This virus is a monster,” said Cornell University epidemiologist Isaac Weisfuse, who was a New York City deputy health commissioner during 2009′s swine flu outbreak. “It seems to find the weaknesses, in terms of people who are susceptible.”

Officials feared a delayed reaction could allow the pathogen to spread. “If you wait for too long, then, because of the epidemiological characteristics of the virus, you are not able to interrupt the spread,” said New York City Health Commissioner Dave Chokshi. “This virus is such a formidable foe.”

The NYC Test & Trace Corps “flooded the area with new testing resources,” Bray said. “We stepped up our outreach.” But it was apparent by the last week of September, she said, that what had worked in other neighborhoods was failing to curb the spread in Borough Park.

On Oct. 4, New York Mayor Bill de Blasio (D) said the cases in Brooklyn and Queens were an “extraordinary problem, something we haven’t seen since the spring.” He proposed wielding a more severe tool — government-ordered shutdowns of schools, businesses and other public gathering places in nine Zip codes. The plan was sent to the governor’s office because state authority is required.

Cuomo greenlit the hot spot shutdowns, but shifted the zone boundaries to be more granular than the Zip codes the city had proposed.

“You have some Zip codes where three-quarters of the Zip codes have no cases,” said a state official, who spoke on the condition of anonymity because he was not authorized to discuss the decision. Defining the zones by Zip code, the official said, would mean placing restrictions on thousands of additional people.

On Oct. 8, the zone rules went into effect. In five red zones, businesses were ordered shut and mass gatherings were made a finable offense. No more than 10 people could meet at a place of worship. Only grocery stores and other essential businesses were permitted to remain open.

Businesses in yellow zones were not forced to close, though gatherings were limited to 25 people, both indoors and out.

Nearly 200 schools closed in Brooklyn and Queens. Hundreds more in yellow zones remained open but were required to test students weekly for the coronavirus. Cuomo warned the state would withhold funding from any school that remained open in defiance of the shutdown.

Agents in the New York City sheriff’s department issued 62 tickets, totaling $150,000 in fines, during the first weekend after the zones were established.

Some residents were up in arms. Borough Park protesters burned masks in the street. The Catholic diocese of Brooklyn filed a lawsuit, as did Jewish congregations in the locked-down areas, because the restrictions limited attendance at places of worship.

Rabbi David Zwiebel, executive vice president of Agudath Israel of America, a national Orthodox Jewish organization, accused state officials of “pointing a finger very explicitly and openly” at the Orthodox community.

Zwiebel’s organization is the lead plaintiff in a lawsuit that claims the governor’s order violates constitutionally protected religious rights. It sought a temporary restraining order to allow worshipers to congregate for holy days in October. That was rejected, and the plaintiffs have appealed.

For both business owners and residents, the restrictions have resulted in “a tale of two boroughs” in Brooklyn, said Peers of the Brooklyn Chamber of Commerce.

“Northern Brooklyn is lively and vibrant” while in Southern Brooklyn, “there’s no restaurant dining options. You can’t get your hair cut. You can’t get your nails done. And these are people’s livelihoods.”

But the restrictions have been largely successful in stamping out virus hot spots. Infections began to decline, and some steeply so, in most communities within a week. By early November, the state downgraded all but one of the red areas to less restrictive designations, allowing schools and businesses to reopen.

Health officials gauge the efficacy of their contact tracing programs in part by measuring the compliance rate — the percentage of people with the virus who confirm by phone they remain inside and alone, unable to infect family members or others. In New York City, that compliance rate is 98 percent, Long said.

“New York City has done a fantastic job,” said Marcus Plescia, chief medical officer for the Association of State and Territorial Health Officials.

The strategy has not worked flawlessly. Positive case rates in Brooklyn’s yellow southern zone have slowly ticked upward. The red zone in its center remains largely shuttered, though the state redrew the map Friday to shrink the area by half, to about four square miles, following a major residential boulevard for dozens of blocks.

To begin the process of reopening, a red zone must show a drop in its seven-day average of positive tests over 10 days. In addition, residents’ test results must remain below a 3 percent infection rate for at least three days.

Though hard on people living in the restricted areas — and officials “ought to make sure they’re applying that strategy equally” — Weisfuse said the micro-cluster method was a better alternative to locking down an entire city. “People get tired of all these regulations that limit their ability to do things,” he said.

A challenging holdout

Lowering infection rates in the last red zone in Brooklyn, which includes parts of the Borough Park, Gravesend and Midwood neighborhoods, has been slow.

In late October, demand for tests at a mobile testing site near a playground in Midwood had slowed to a trickle. A month ago, a site like this — a few pop-up tents and a van — would have tested 150 people a day, said Luis Mendoza, a city worker who registers people before testing them for the virus. But early into the second week in this zone, only 10 people had been tested by midday.

He and other city workers were struggling to convince some members of this tightknit community to get tested. “They don’t know if they have the antibodies, or if they even have the virus,” Mendoza said. “They could be spreading it around.”

Behind the testing tents, past a tall chain link fence, several children played on an asphalt court supervised by women, wearing the modest dress typical of the Hasidic faith. None wore masks, in apparent violation of a state rule that mandates face coverings when in public and not socially distanced.

Not far away, just beyond the boundary of the red-zone hot spot, an older woman in a mask walked her dog.

“I’ve had people say in the streets to me, ‘Why are you wearing a mask? You’re outside [a building].’ But if somebody coughs four feet in front of me and I walk into it. … I lost my husband to it,” said the woman, who lived in the Gravesend neighborhood and spoke on the condition of anonymity because she was critical of her maskless neighbors.

Tears welled in her eyes above a tie-dyed blue mask printed with cartoon dog bones. “It’s just so annoying seeing people so blatantly avoiding something that could save lives,” she said, gesturing down the street, toward the red zone. “So many people down that way. No masks.”

Read more: