Caution tape is seen wrapped around a playscape at the Still Street Playground which was closed as part of an effort by the town of Brookline to reduce the spread of coronavirus. Jessica Rinaldi/Globe Staff

The staggering scope of the coronavirus pandemic came into increasingly stark focus Monday as the MBTA announced it would cut back on service, schools across the state prepared to close for weeks, and Boston ordered a halt to major business and city construction projects, bringing a longtime building boom to a standstill.

“The coronavirus is one of the greatest public health challenges our city has ever faced,” Mayor Martin J. Walsh said at a City Hall news conference.

The number of cases in the state climbed to 197, up from 164 on Sunday, as the pace of testing accelerated. The state Department of Public Health said that nearly 1,300 coronavirus tests had yielded 189 positives. The other eight positives came from tests by the US Centers for Disease Control and Prevention.

More than half of the positive tests are related to a conference last month by the biotech firm Biogen. No one has died from the virus in Massachusetts. Nationally, at least 80 people have died, and the global death toll has surpassed 7,100.

Health care providers at Massachusetts General Hospital and Massachusetts Eye and Ear have tested positive, the hospitals said, and dozens of health care workers who may have been exposed are in quarantine. Two doctors at Brigham and Women’s Hospital have also contracted the virus and are in home quarantine, and Northeastern University, which had already announced that it would move all classes online starting this week, said that a student there had tested positive, the first presumptive case at the school.

Governor Charlie Baker, who over the weekend issued sweeping restrictions to halt the spread of the deadly pathogen, said he was not considering a shelter-in-place order — a move that San Francisco announced earlier Monday.

Construction workers at the Omni Hotels & Resorts in the Seaport in Boston call it a day, as the mayor ordered a halt to construction projects today. David L. Ryan/Globe Staff

“We don’t believe that’s an appropriate decision to be made at this time [in Massachusetts] given the facts that are on the ground,” Baker said at a State House news conference. But “nonessential gatherings of any significant size, given the contagious nature of this particular virus, are just simply a bad idea,” he said.

Over the weekend, Baker ordered that all public and private schools close for at least three weeks, limited all restaurants to takeout and delivery, and prohibited gatherings of more than 25 people, policies that go into effect Tuesday. That limit applies to all community, civic, public, leisure, and faith-based events, as well as sporting events with spectators, concerts, and conventions. It also covers fitness centers, private clubs, and theaters. The governor stressed that grocery stores and pharmacies would remain open.

“You can’t get into the business of denying people access to things like food and medicine," Baker said Monday.

With astonishing speed, the coronavirus has impacted nearly every sector of public life here. With workers increasingly hunkering at home, the MBTA announced that it would cut its weekday service. Starting Tuesday, the subway and most bus lines will follow a Saturday schedule and the ferries will be closed, the agency said.

The collapse of ridership has been obvious to anybody who has stepped on a train in recent days. But on Monday, the agency released numbers for last week, showing a gradual but steep drop as the region fell into crisis. By Friday, station entries on the subway and Silver Line were down 48 percent compared to a more typical week in February, according to the T’s preliminary data analysis.

At the beginning of the workweek, many businesses around the city had already closed or ordered employees to work from home. But Boston’s large construction sites, emblems of the city’s recently bustling economy, were still operating at full capacity. Walsh said those sites would close on Tuesday but companies should maintain skeletal crews to make sure their sites are “safe and secure.”

“The only work that we’re anticipating right now moving forward in the city will be emergency work," such as emergency street repairs and utility hookup work, Walsh said.

Alluding to the enormous economic impact of the construction site closures, which Walsh said would affect tens of thousands of people, the mayor urged employers not to fire workers.

“I want to remind Boston’s employers that we are in a robust construction market,” he said. “When we are back to business as usual, employers will need to bring these workers back. The right thing to do is lay them off, not fire them.”

Walsh said the construction ban could be over in 14 days “and then we’ll revisit it and hopefully they can be the first workers back to work.”

The city’s public libraries and Boston Centers for Youth and Families gyms and pools will also close, the mayor said, and all BCYF programming will be suspended, although a few centers will remain open to distribute meals to some of the 54,000 students who will be affected by the closure of Boston Public Schools starting Tuesday. Although Baker said schools in the state must close for three weeks, Walsh ordered BPS schools to be closed for double that time, until April 27.

“This is a critical time for us right now to prevent the spread,” Walsh said. “If we can prevent the spread from happening and try to level the virus off, we’ll be in a better position long term.”

The school shutdown will keep more than 1 million Massachusetts students out of the classroom, but the state has decided to leave open child-care centers.

Both Walsh and Baker announced steps on Monday to help stem the economic toll of the virus, particularly for workers and small businesses who will be affected by the near economy-wide shutdown. Walsh introduced the Boston Resiliency Fund, a partnership between the city and several leading philanthropic institutions that will grant money directly to local organizations and nonprofits that support Boston families.

The focus of the funds will be food access, technology for kids who will be distance learning, and “support for our health care workers and first responders, including child care,” the mayor said. The schools purchased tens of thousands of Chromebooks last week to supplement the ones it already owns, with the goal of equipping every student in grades 3 through 12 with a computer.

At his press conference, Baker announced a $10 million loan program for small businesses affected by the virus and its economic impact. Businesses with fewer than 50 employees can apply for up to $75,000 of emergency funds and would have loan payments deferred for six months, Baker said.

Residents will wake up on Tuesday to an entirely new normal, with schools shut, businesses closed, and nearly all gatherings canceled. In an interview with WGBH, Walsh was asked how he would respond to city residents who feel he and Baker are being extreme.

“I hope we’re going too far," Walsh said. "I hope in three weeks, people can say, ‘you did too much.’”