Boston Mayor Martin J. Walsh recently visited his mother, Mary, in the triple-decker he grew up in on Taft Street in Dorchester to deliver a coffee.

It was the third week of March, and he had a lot on his mind. He was facing the biggest crisis since he became mayor more than six years ago. The coronavirus caseload was climbing, and the emergency was forcing him to make one big decision after another, decisions that dramatically shut down everyday life in Boston as Walsh scrambled to mitigate the disease’s deadly spread. In the span of a week, he would nix the St. Patrick’s Day parade, close the state’s largest school district, and suspend the vast majority of construction in the city.

On Sunday, Walsh asked city residents who aren’t essential workers to observe a curfew from 9 p.m. to 6 a.m. and encouraged everyone to wear masks when they are outside.

The outbreak even changed a simple act: a son popping by for a chat with his mom.

Walsh did not hand his mother the coffee, a regular from Greenhills Bakery. He set it down on a table, where she could pick it up. He washed his hands, but he didn’t hug her, social distancing being what it is.

And before he left, he told her he loved her and reminded her to wipe down all the door handles he had touched.

“I’m worried about all of us,’’ Walsh said later.

Amid the pandemic, Walsh has relied on his vast network of contacts across the city to gather information, process the fast-moving crisis, and gut-check his decisions, according to interviews with the mayor and more than a dozen civic, political, and business leaders in the region.

He has also been anchored by family and the one-day-at-a-time creed that has helped him stay sober for more than 20 years, as other routines that have kept his feet on the ground have disappeared.

Walsh, who has held New England Patriots season tickets for decades, used to unwind after a long day by watching sports. But with live sporting events gone, there is now more time for him to contemplate his decisions.

If he can, Walsh will watch “Seinfeld’’ or “Modern Family’’ “to get a laugh in,’’ but consuming the news often fills his hours away from City Hall. He said he wants to get a feel for what is happening in other places as the crisis rages on.

Typically, Walsh, 52, tries not to take the job home with him.

“This is different,’’ he said. “This comes home with me every day. When I wake up it’s in my head. When I leave it’s in my head.’’

On weekends, he said, he goes for walks and asks himself: “Are we doing it right? Are we doing it fast enough?’’

“There’s no playbook for this,’’ he said.

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A week and a half before the city’s biggest annual party, the South Boston St. Patrick’s Day parade, Walsh was expecting to have a broad conversation about the economic forecast with Eric S. Rosengren, president of the Federal Reserve Bank of Boston.

Instead, he spent much of the 30 minutes listening to the economist warn of the growing threat of the novel coronavirus, how Italy was being brought to a standstill by the outbreak.

Later that day, March 4, he spoke to Dr. Jeffrey Leiden, the chief executive of Vertex Pharmaceuticals, a Boston biotech giant. He, too, had coronavirus concerns.

Leiden said it was clear to his company at the time that the coronavirus problem was going to become a much larger emergency, and quickly.

According to Leiden, the two talked about three prospective stages of the crisis: the initial need for more testing and the necessity of social distancing becoming a norm, the need for more medical facilities and what would be needed for medical treatment, and lastly how to reopen everyday services once the brunt of the pandemic was over.

Given how quickly the outbreak spread, timing was everything, Leiden said in a telephone interview. Leaders who waited a few days or a week to make a decision had “a real problem.’’

“He’s stayed two steps ahead of it,’’ Leiden said of Walsh.

Such discussions brought the severity of the problem into sharp relief for Walsh.

The following day, March 5, the Cambridge biotech giant Biogen said three of its employees had tested positive for the coronavirus after attending a conference at a Boston hotel. The event, at the Marriott Long Wharf Feb. 26-27, would become an epicenter of coronavirus cases locally, with more than 100 directly linked to the conference.

In the days that followed, Walsh talked to infectious disease specialists and South Boston elected officials. The improbable started to seem like the right path forward: canceling the St. Patrick’s Day parade, which can draw a million or more revelers to Southie’s sidewalks, barrooms, and house parties.

Among those Walsh reached out to was US Representative Stephen Lynch. He knew Lynch would be briefed on the coronavirus situation nationally. He told the congressman his inclination was to cancel the parade, and Lynch told him it was the right move, saying, “I don’t think you have any choice.’’

“Now it looks like the obvious decision,’’ Lynch said recently. “But people weren’t of a single mind.’’

Five days after Walsh spoke with Rosengren and Leiden, the mayor announced this year’s parade would not happen.

There was some initial pushback on social media.

“I’d rather be cautious and be criticized later if it doesn’t turn out to be as bad as at that point we thought it could be,’’ Walsh said.

The canceled parade was just the first of what would become a cascade of significant calls for Walsh.

Another huge, local event was looming: The Boston Marathon, the oldest annual race of its kind in the world, was slated for April 20. The event injects about $200 million into the Boston economy each year, drawing runners from around the world.

At news conferences, Walsh was peppered with questions about the Marathon. Publicly, he mostly demurred.

Privately, he knew “there was no way we were going to have the Marathon in April.’’ He had continued to speak with public health experts and had seen modelling for the virus’s spread on both national and local scales. It was going to get a lot worse.

Several days of talks with the Boston Athletic Association and other local officials followed.

As the Marathon discussions unfolded, Walsh was also wrestling with what to do to keep the city’s 53,000 schoolchildren safe.

On March 11, the authorities announced that the three North End campuses of the Eliot­ K-8 Innovation School were to be closed for a week because of a presumptive positive case of coronavirus in a “non-student member of the community.’’

That case brought urgency to ongoing discussions about what to do with the entire city school system.

“That was definitely a turning point for us,’’ Superintendent Brenda Cassellius said.

As the week progressed, a bevy of nearby school districts announced closures. Walsh and Cassellius considered the complications presented by a districtwide shuttering of schools.

It would be a massive disruption to tens of thousands of families. Not all students had laptops and Wi-Fi access, which presented a hurdle for virtual learning. There were considerations to be made for special needs students in the event of a prolonged period of remote lessons. Additionally, almost three-quarters of the district’s students relied on free meals they received at school. Coming up with a plan to feed students who would no longer be physically in schools became crucial.

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Friday the 13th came with a host of pandemic-related announcements. President Trump declared a national emergency. Officials said that the Boston Marathon would not run on Patriots Day for the first time in its 124-year history. Walsh’s office has described its postponement as a city decision made in consultation with the other municipalities along the Marathon route. The race is now scheduled for September.

“That might be the first event that brings us back to some normalcy,’’ Walsh said recently.

Hours after the Marathon news, Walsh announced that starting on March 17, schools would be closed for at least six weeks, a decision that would throw family life into turmoil across the city as parents rushed to find child care while they went to work, or attempted to keep children busy at home.

The city would use its youth summer meals model, which offers a grab-and-go food service, to feed students who need the meals during the coronavirus emergency.

It would also buy 20,000 Chromebooks for students who had no computers at home. The $5.5 million purchase was made through a combination of city funds and private donations.

Jessica Tang, president of the Boston Teachers Union, would later praise Walsh’s administration for being among “the first in the nation of large urban districts to recognize that the scope and severity of this crisis required the closure of schools.’’

“By working with educators to close the schools earlier than in many other places across the country and by providing meal and housing relief, we are confident that lives were saved,’’ Tang said in a recent statement.

The following day was Saturday. And, despite growing unease about coronavirus, a photo that went viral on social media showed a long line of revelers at a South Boston bar. There were other bar queues in the neighborhood, as well. The parade may have been canceled, but it was still St. Patrick’s Day weekend in Southie, and lots of people were looking to celebrate, social distancing be damned.

Lynch, the congressman, snapped photos of the lines to get into bars and sent them to Walsh. A reply came back: “I’m on it.’’

Walsh said he was already aware of the situation, and he directed the city’s licensing board and police to contact the managers of the establishments who were seeing crowds. He wanted city authorities to convey that what was happening was “unacceptable and inappropriate.’’

“In fairness to the folks in line that day, I don’t think they quite understood the severity of this,’’ he said. “Certainly I did.’’

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Walsh, who has been open about his past struggles with alcoholism and having been sober for more than 20 years, credits the one-day-at-a-time approach that has been crucial in his recovery with helping him navigate the COVID-19 catastrophe. He said he cannot spend much time focusing on the potential length of the emergency.

“I focus on what’s in front of me,’’ he said.

Walsh participated in his first online Alcoholics Anonymous meeting in late March. Earlier in the month, he got together with a few people in a parking lot for an AA meeting marked by social distancing.

Walsh said he still tries to talk to a few people in recovery each day.

“Just knowing that they’re there and I’m there for them, that’s really important,’’ he said.

Walsh’s professional day-to-day has become more structured amid the pandemic, he said.

No more glad-handing. Lots of calls.

There is a daily 8 a.m. call with his City Hall team, usually followed by a 10 a.m. call with city councilors and even more conference calls throughout the day. He said he speaks to Governor Charlie Baker almost every day. Then there are calls with legislators, with other mayors, with health care leaders.

Kevin Tabb, chief executive of Beth Israel Lahey Health, described Walsh as responsive during this crisis. Bureaucratic barriers in the city, said Tabb, have not been a problem as the pandemic has unfolded. Tabb said he has been in contact with the mayor or his office almost every day.

“I cannot think of a single time when I’ve needed something and when I’ve reached out and it’s taken more than five minutes for him to get back to me,’’ he said. “I’m very, very impressed.’’

Dan Koh, a former chief of staff for Walsh, said the mayor enjoys keeping a schedule packed with community events to stay close to the city he governs.

In the time of coronavirus, burning up the phones on a daily basis may be the best proxy for that experience, Koh said.

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On Sunday, March 15, the day of the canceled parade, Walsh declared a state of emergency. A day after the bar queues in Southie, he unveiled a slate of new industry guidelines: restaurants, bars, and clubs were to reduce capacity by half and adhere to social-distancing guidelines.

Later in the day, Baker would make such restrictions moot, ordering schools to close statewide, making restaurants across Massachusetts move to take-out and delivery only, and barring gatherings of more than 25 people.

The next day, Walsh announced he was suspending the vast majority of construction in the city, another blow to the local economy.

In a rare rift, the ban would eventually put Walsh at odds with the governor. Later in the month, the Baker administration sent a letter to cities and towns emphasizing its stance deeming construction an “essential service’’ that should continue, despite the governor’s stay-home advisory.

Walsh called that decision to suspend construction a personal one; he had worked on construction sites and was formerly the head of a local building and construction trades council. His father, John, who died in 2010, was a laborer. While organized labor helped propel the mayor to power, Walsh said he did not consult any unions before making the call.

“On a lot of this stuff, there isn’t time for consultation,’’ he said.

Walsh said that if office workers are being sent home, construction workers should be as well. There are times when social distancing is not possible, given the demands of the work. “Not everyone wants to go home, but I don’t make a decision based on being popular,’’ he said.

At the same press conference he announced the construction suspension, Walsh outlined plans for the Boston Resiliency Fund, which is intended to provide high-priority critical services in the city as the crisis evolves. Already, the fund has surpassed its fund-raising goal of $20 million.

Kate Walsh, the chief executive of Boston Medical Center, said that while the mayor leads a city that has an enormous amount of health care expertise, “he cares about people who may not have access to that.’’

When a tent designed to help the homeless during the pandemic outside the Southampton Street shelter was poised to open, there was a shortage of personal protective equipment. There were questions about whether the tent’s operations could start without such supplies. Walsh used his contacts in the construction world to get masks to the workers, allowing the workers at the tent to start serving the homeless community.

“He’s really been connecting the dots and calling in a lot of personal favors,’’ said Walsh, of no relation to the mayor.

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As the coronavirus has taken its grim toll across Boston — with more than 1,800 confirmed cases and at least 15 deaths of city residents — the pace of difficult choices facing Walsh has rarely let up. Still, Walsh manages to speak to his mother every day, by phone. On one recent day, she told him a story that stuck with him.

His grandfather, Joseph O’Malley, as a teenager in County Galway, Ireland, contracted the Spanish flu in 1918. He survived the disease, which killed tens of millions worldwide, but his sister, Barbara — Walsh’s great aunt — did not. She was 16 when she died.

“I didn’t know that story until my mother told me,’’ Walsh said. “That’s exactly what we’re trying to prevent today.’’

Danny McDonald can be reached at daniel.mcdonald@globe.com. Follow him on Twitter @Danny__McDonald.