Tom Lynch hadn’t expected the world to change—or at least his perception of it—at his Tuesday morning leadership meeting. He had expected to talk about the fiscal year 2021 budget and maybe to get to know his team a little better. It was Feb. 25, and Lynch was just four weeks into the job as director of the Fred Hutchinson Cancer Research Center, so new that as he walked the halls of the Hutch that morning he struggled to find the right conference room.

Lynch had also made time on the meeting’s agenda for Trevor Bedford, an epidemiologist at the prestigious Seattle-based research institute who had been tracking the novel coronavirus known as SARS-CoV-2 since early January. Lynch describes Bedford as “very humble” and “understated,” but that morning, as the quiet computational biologist laid out his grim projections for the virus’s impact on Seattle, he held the room. People became incredibly quiet and just listened,” says Lynch. “Everyone in the room at the same time got that what he was talking about was something that was going to really change our lives.” Lynch vividly recalls that day. “You remember where you were when you realized what this was.”

What this was was still a completely unfathomable proposition for most in the global metropolis of 3.5 million. “Social distancing” had not yet entered the lexicon. At the time, Seattleites were still making arrangements for March tech conferences and spring fund¬raising galas; people were looking ahead to attending Seattle Storm games and Patti Smith concerts and the Emerald City Comic Con, a beloved annual gathering of 100,000 superfans slated for mid-March.

If people knew it at all, COVID-19 was a threat that seemed at least an ocean away. The State of Washington had reported just one known case, that of a 35-year-old man from Snohomish County outside Seattle, who had traveled to Wuhan and gotten sick upon his return in mid-January. He’d been treated and recovered. For those keeping score, it was Washington–1, coronavirus–0. But on that morning in late February, Bedford framed the situation quite differently; the virus was an urgent if not yet visible existential threat. Lynch got the message, and the next morning, in a breakfast meeting with Fred Hutch’s board leadership it was Lynch who upended the agenda.

“I think we should spend this entire conversation talking about COVID-19, and what’s very likely to be coming down the pike here in Seattle,” Lynch said to his chair Matt McIlwain, a managing director at Madrona Venture Group, the Seattle-based venture capital firm. McIlwain left and immediately called his VC colleagues: “We need to think through what our strategy is,” he said.

Another person looking at Bedford’s data was Christine “Chris” Gregoire, a former Washington state governor—she served from 2005 to 2013—former Fred Hutch chair, and now head of an organization called Challenge Seattle, which engages 19 of the city’s largest businesses and institutions. Those include a striking number of name-brand Fortune 500 companies and organizations,including Amazon, Microsoft, Starbucks, Costco, Boeing, Nordstrom, Alaska Air, and the Bill & Melinda Gates Foundation, among others. The group was founded to solve some of the region’s more intractable problems surrounding education, affordable housing, and transportation. As it happened, Challenge Seattle had one of its meetings on the night of Feb. 25.

Challenge Seattle chair Susan Mullaney, the president of Kaiser Permanente Washington—which has dozens of health facilities, a leading research center, and more than 700,000 members across the state—had been following, with increasing alarm, her own group’s COVID-19 modeling efforts. She asked Gregoire for some time on the agenda that night; this was something she thought the business community needed to prepare for.

Many attendees now remember the event as their psychological turning point. Earlier in the evening, they’d casually discussed the virus over wine; at dinner, they’d sat—as one did, pre-pandemic—tightly bunched around tables. Though a few were already bumping elbows, many shook hands.

“I gave a brief update on how bad we thought it would be,” says Mullaney. Gregoire went over Bedford’s projections. As the group, which included Weyerhaeuser’s Devin Stockfish, Zillow’s Rich Barton, and REI’s Eric Artz, talked through comparisons to the 1918 flu pandemic, it was lost on no one that the most concerned among the group were its subject-matter experts—Mullaney and Steve Davis, the recently retired CEO of PATH, the global health organization. Some were struck by the assessment that the CDC was six to eight weeks behind on the issue. “The severity of it was sinking into all of us during that dinner,” says Michelle Seitz, CEO of Russell Investments, the Seattle-based global asset manager.

Margaret Meister, head of Symetra Financial, an insurance giant based in Bellevue, the Seattle suburb, had been so startled she texted her leadership team that night. “We need to up our game. This is a crisis. This is not some small thing,” she told them.

“Quite candidly, there was absolute shock around the table,” says Gregoire. “That was the day that everybody saw how dire this could be if we didn’t get to work.”

What nobody imagined was how quickly things would turn. Just three days later, public health authorities announced the state’s second confirmed case of COVID-19. It was a stunning one: The infected individual was a local teenager, a high school student also from Snohomish County but who hadn’t traveled anywhere. (His case had been detected only because the Seattle Flu Study, an influenza surveillance effort funded by Seattle-based Gates Ventures and staffed by University of Washington, Seattle Children’s Hospital, and Hutch scientists—Bedford among them—ignored state and federal guidelines and tested samples.)

And then the following night, a Friday, Gregoire got a call. The state had its first COVID-19 death, and there was an outbreak at a local nursing home. The virus was in the community, and it was spreading. The threat they’d all been worrying about had already arrived.

But something else had been spreading too. The networks that knit Seattle together—running from its research hospitals and global businesses to world-eminent institutions, community organizations, and government—were thrumming with the exchange of information and intentions. Gregoire immediately called Mullaney and asked her to prepare another briefing.

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There are many ways to tell the story of America’s first COVID-19 outbreak—an epidemic that, in the Greater Seattle area, has to date tragically killed 385 and infected 7,324 (in King County, home to Seattle proper, the numbers are 294 deaths and 4,428 infections). The virus has stolen the livelihoods of hundreds of thousands more. But the story of how Seattle came together can be a model for any city and organization.

In some ways, it’s hard to dream up a city better equipped to manage an outbreak of a new and deadly pathogen. Seattle has few worthy rivals when it comes to public health. In the University of Washington, the city has one of the nation’s leading virology labs and one of its largest infectious disease departments. It’s a town full of influential epidemiologists and disease modelers, many of whom have had their efforts blessed with Gates dollars, from the Hutch’s Bedford—with 200,000 Twitter followers—to the University of Washington’s Chris Murray, whose models are cited by the White House. It’s no accident that Seattle has the world’s first operational trial site for a COVID-19 vaccine candidate, or that it’s the first city in the country doing COVID-19 surveillance with at-home testing kits.

“We have an infrastructure that is 40 years in the making,” says Larry Corey, the man who started UW’s virology program in 1978 (and has since been instrumental in developing AIDS drugs, helmed the Hutch, and led the global HIV Vaccine Trials Network). “We’ve been able to permeate our community…we’re able to influence and be a factor.”

Seattle is also a city of staggering wealth, home to a burgeoning tech community as well as the world’s most valuable multinational companies and the world’s two richest men, one of whom, Bill Gates, just so happens to be the planet’s most prominent advocate and funder of pandemic preparedness. Beyond those deep pockets, these enterprises are well connected to expertise—logistical, technical, biomedical—that spans the globe.

It all adds up to a highly educated population—with 62.6% of its residents holding four-year degrees, it was dubbed “America’s most-educated big city” in 2019—with a bias toward data and science. (Some also credit locals’ Scandinavian reserve—which manifests as the “Seattle freeze”—for their success at social distancing.)

Two Twitter hashtags epitomize the city’s collective response. #AllInSeattle—a fundraising banner under which dozens of the city’s millionaires donated $27 million to various nonprofits in four days—and #WeGotThisSeattle, a hashtag that trended on Twitter and was stitched on a flag that now crowns the city’s iconic Space Needle.

That’s not to say the city is out of the woods—Washington State Gov. Jay Inslee has stressed this point repeatedly—but in recent weeks as COVID-19 has continued its devastating spread across the U.S., Seattle has found a bit of a clearing, or in epidemiologist-speak, some “curve bending.” Its hospitals, though constrained by resources, have not been overwhelmed like those in New York and New Orleans. In King County, where Seattle and many of its suburbs lie, ¬COVID-19 cases today are doubling once every 15 days; that compares with every 11.5 days in New York City and every 8.5 days in Chicago. Supplies once destined for America’s ¬COVID-19 ground zero are now being rerouted to new, hotter hot zones.

In that way, the city offers a playbook, one that points to the importance of collaboration. Seattle is a big global city, but as many Seattleites will tell you—powerful ones, at least—“it feels a lot like a small town.” Information, and aid, and solutions were being rapidly passed around Seattle’s tight-knit business community and throughout the ranks of government. Suddenly some of the most cutthroat companies on the planet, like Amazon and Microsoft, weren’t trying to fight for market share, they were on the same side for once, trying to save their city.

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Brad Smith hadn’t expected to come home to find an outbreak in his backyard. As Microsoft’s president, he’d been thinking about the virus, certainly—he’d been at a security conference in Munich mid-February, where he’d met a team from the White House who had peppered him with questions: What had the company seen in China? What would be the ripple effect of China’s economic downturn? Smith had then gone to Rome for an event at the Vatican; as the outbreak worsened in northern Italy, the virus was top of mind. He had left Italy the night of Friday, Feb. 28.

On Feb. 29, local public health authorities announced its first COVID death, an outbreak at the Life Care Center in Kirkland—a short drive from Microsoft’s campus. Adding to the urgency, Hutch epidemiologist Trevor Bedford shared an analysis, based on genomic-sequencing data of the virus, that suggested SARS-CoV-2 had been stealthily circulating in the community for weeks, likely infecting hundreds. Smith, a history buff, did two things: He ordered the best-regarded book on the 1918 flu pandemic, John Barry’s The Great Influenza, and he phoned his friend Gregoire, who had called for an emergency meeting of Challenge Seattle members the following day. They discussed the need to gather leaders from both the private and public sectors—and particularly public health experts.

The next day Gregoire held the emergency meeting, becoming the first in what is a now an ongoing series of daily COVID-19 crisis calls, open to the entire business community, sometimes with as many as 200 participants. At the beginning though, it was a much smaller group of leaders and King County officials trying to establish the facts and coordinate a response in an effort to “build public confidence,” says Gregoire.

They decided, when possible, organizations—even fierce competitors, like Amazon and Microsoft—should respond in the same way, whether it be on work-from-home policies or protocols around essential employees. Those companies also got a heads-up whenever local or state officials were planning to announce outbreak-related policies. “So these big companies began acting in concert,” says Gregoire. “I’ve had a career in public service, and I’ve never seen anything like this.”

Within days of the group’s first call, many of the city’s largest employers had asked all but their essential workers to stay home. Microsoft went on to announce it would continue to pay its hourly workers—janitors, cafeteria staff—while the campus was closed. Others, like Amazon and Expedia, followed suit.

But the virus didn’t wait for the business community to get its bearings. It had already crossed into Seattle’s corporate sector.

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Like many of Seattle’s tech leaders, François Locoh-Donou, CEO of $2 billion F5 Networks, was planning for business as usual as February drew to a close. There was an investor and analyst event in New York, then the company’s annual customer meeting in Orlando mid-March.

But late on Friday, Feb. 28, his HR chief had taken him aside. There had been just three confirmed COVID cases in the whole state of Washington then, but one of them had been in close contact with an F5 employee. That employee—whose own COVID test results wouldn’t be available for a few days—had been coming to work, riding the elevator, and occupying space in the company’s new, 48-floor office tower.

That raised all sorts of questions—familiar now, but quite novel then. Should they close the office tower? Should they forgo their events? Had they themselves been exposed? Working out of a conference room that weekend, F5’s leadership team scrambled to consult experts and formulate a plan. “We had to make decisions really quickly,” says Locoh-Donou. They closed the tower for cleaning, a fact that more or less forced the other decisions: “We couldn’t send 10 executives from F5 Tower to be in a room with investors in New York City,” he says.

The decision hurt nonetheless. The employee tested negative, but the last-minute cancellation of the investor event spooked the market, and F5’s stock price took a beating. For a couple of days, “it looked like a bad decision,” says Locoh-Donou. Of course, he adds, it was the right call.

Within days the city’s other tech companies were dealing with similarly urgent decisions. Amazon emailed employees on Tuesday, March 3, about a confirmed case on its Seattle campus; the individual—one of the company’s 50,000-plus based in Seattle—worked out of the headquarters’ Brazil building and had last been in the office on Feb. 25. The night before falling ill, that employee had eaten dinner at Facebook’s nearby Seattle campus.

Facebook, meanwhile, had its own confirmed case—a contractor who had last been in the company’s local offices on Feb. 21. Microsoft reported a case on its Redmond campus, peopled by roughly 50,000 employees, on March 5.

“People wanted to know what floor they were on or what room they were in,” says Kathleen Hogan, Microsoft’s chief people officer, who got word of the confirmed case on their campus over text. Microsoft benefited from the expertise of Colleen Daly, the company’s global wellness benefits manager, who holds a Ph.D. in public health. Daly was on daily calls with the CDC and World Health Organization and managed the company’s internal contact tracing efforts.

For the city’s tech companies, many of which are in the business of enabling the burgeoning work-from-home economy, issuing swift and sweeping guidance for their employees was relatively straightforward. The calculation was not so simple for some of Seattle’s other large employers.

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Having closed down 80% of its stores in China during the outbreak, Starbucks already had experience with COVID-19 when the virus showed up in its hometown. When a staff member in a downtown Seattle store came down with the disease on March 6, the company sanitized the store and resumed operations a few days later. The company phased in other changes—like offering 14 days of catastrophe pay to Covid-impacted workers and removing seating. But as the outbreak intensified across the U.S., employees like Aniya Johnson of Philadelphia grew frustrated that they were being asked to risk their health to serve coffee. “It’s not an essential service,” Johnson told Fortune in mid-March, days after she had, on a whim, started an online petition calling on Starbucks to close stores during the pandemic. The effort attracted 37,400 signatures from baristas and customers by the time Starbucks announced it was moving primarily to a drive-through model. (Starbucks says its decisions were informed by the China experience and grounded by concern about the well-being of its employees and communities, and its desire to support governments in efforts to mitigate the virus’s spread.) Costco—whose stores were deluged nationwide with shoppers seeking toilet paper and canned goods—asked employees at its headquarters, just east of the city, to report to work. That request was dropped after an employee in the company’s travel department died of COVID-19 and others tested positive in mid-March.

Boeing, which employs roughly 35,000 at its largest factory in Everett, just north of the city, and 70,000 in the Puget Sound region, initially kept its plants running. Deemed an essential business, its lines continued to assemble airplanes as COVID-19 cases cropped up in its workforce; it suspended production in the state in late March following the death of a quality inspector named Elton Washington.

While some Seattle employers struggled to strike the right balance, the area’s health care providers were scrambling to prepare for a surge of patients amid a desperate shortage of tests and other critical supplies. The Providence Regional Medical Center in Everett, which had received the nation’s first COVID-19 case in January, had tried to bulk up on supplies for a potential pandemic that month.

“Even being a couple steps ahead in our planning, it was really a challenge,” says Amy Compton-Phillips, chief clinical officer for the system. Starting in January, Providence’s orders from suppliers in China couldn’t be filled because manufacturing lines there were down. Providence staffers were overwhelmed by offers from suppliers they’d never worked with before, and came to understand many of them were profiteers, hawking non-medical-grade goods. “Things got so bad that we just went out to Joann Fabrics and Home Depot and bought supplies,” adds Compton-Phillips. A local Seattle TV station did a news story, featuring footage of Providence’s nurses assembling face shields and surgical masks in a hospital conference room.

Jeff Kaas, CEO of Kaas Tailored, a local company with 200 employees that makes furniture for Nordstrom and airplane parts for Boeing, heard about the spot on March 18 and immediately texted a doctor friend at Providence: “You know I have a factory, right?”

The next morning at 6 a.m., Providence sent a design and supply team to Kaas’s Mukilteo, Wash., factory. They worked out a surgical mask prototype, and the following day, after some collaboration with a firm in the Netherlands, they were making them. Kaas shared the specs online, which are now being used to produce personal protective equipment (PPE) around the world.

His own factory, staffed by employees, volunteers, his wife, and all four of his children, has been running 16 hours a day, six days a week since. Nordstrom has lent tailors to the effort and placed one of its managers at Kaas’s factory full-time. Providence’s effort has grown into the “100 Million Mask Challenge,” managed by the American Hospital Association.

Outdoor Research, a Seattle-based outdoor- and military-apparel maker owned by Dan Nord-strom—he left his family’s department store business in 2002—has also transitioned his operations to make PPE, an effort that was celebrated by Gov. Inslee as the sort of wartime manufacturing effort that’s needed. Local institutions have also stepped up to fill testing and health care gaps. The University of Washington has quickly ramped up its operations to run 2,000 tests per day. The Gates-backed flu study has pivoted to doing COVID-19 surveillance using at-home swab kits that Amazon delivers.

A Seattle-based financier with connections to China reached out to Madrona’s McIlwain in mid-March, offering to set up a video call between ICU and ER doctors in COVID-19-impacted Chinese cities and their counterparts in Seattle. Two days later, with the help of the Hutch, the information-sharing session took place over Zoom at 6:30 a.m. Seattle time, with 300 participants nationwide.

While Challenge Seattle initially focused on synchronizing the actions of the business community, the group’s efforts quickly turned to troubleshooting and supporting the government too.

When Kaiser Permanente’s Mullaney asked the group in early March, “Can anybody help get basic supplies?,” Costco CEO Craig Jelinek responded, saying he could source 40,000 N95 masks from China in 24 hours. Alaska Air CEO Brad Tilden made a broad offer to transport supplies. “We’ve got a fleet of airplanes that we’ll put at your disposal,” he told Mullaney.

Later, when a representative from Washington State mentioned on a call that it needed to make an advance payment to secure $10 million worth of protective equipment from China, Microsoft that day made available $15 million to the government to assist.

In another instance, a quarter-million N95 masks Microsoft had managed to procure for the state were stuck at a FedEx import facility in Memphis. Smith got wind of this dilemma at 5 p.m. on a Saturday in late March. He made a call to the White House, a contact on the National Security Council. They were released by the next morning.

“Anything the government has asked of these companies they have stood up and said, ‘We can make that happen,’ ” says Gregoire.

When Challenge Seattle asked for help organizing the state’s medical supply distribution center, they got senior managers from Amazon and Microsoft. When King County needed furnishings for motels they had turned into quarantine centers, Gregoire says Starbucks came through with furniture. After Mullaney advised that the state needed a single point person to coordinate its hospitals during the outbreak, her team helped Gov. Inslee find and hire—in roughly 72 hours—Vice Admiral Raquel Bono, a trauma surgeon who set up field hospitals in Desert Storm.

By early April, there were very real signs of hope that these types of moves had helped Seattle had escape the worst-case scenarios. Gov. Inslee sent 400 ventilators Seattle no longer needed to the East Coast. Supplies to turn CenturyLink Field, where the Seahawks play, into a temporary hospital were instead directed to other states.

In assessing the catastrophic toll from the spread of this deadly pathogen, in most places COVID-19 seemed to reveal nothing but weakness: weakness in infrastructure, weakness in supply chains, weakness in preparedness, divisions between government and business. In Seattle the pandemic seems to have revealed something else entirely: a tensile strength that few knew the city possessed. Says Smith: “If you bring us all together and coordinate the right way, you can do so much more together.”

The city’s dense web of partnerships has proved vital in stemming the initial wave of contagion; it’s unclear if it will be as effective in addressing the collateral damage COVID-19 has wrought—a devastated economy, record-level unemployment, and fissures of inequality the crisis has laid bare.

These are new realities with no easy answers, but Seattle has an advantage when everyone is #AllIn. 

A version of this article appears in the May 2020 issue of Fortune with the headline “Seattle Under Siege.”