Much of life in America, and across the globe, has ground to a near halt in recent days as the coronavirus spreads, closing schools, thwarting travel, forcing employees to telework and shuttering beloved institutions. Authorities now believe the outbreak could fundamentally upend society for months.

The sweeping, unprecedented shutdown of activity in the United States accelerated in seemingly no time, with the week starting out like almost any other and ending in a way few can comprehend.

President Trump declared the virus a national emergency Friday, which can be helpful for marshaling resources, and Congress reached a deal on a broad relief package. Governors in Pennsylvania and Virginia closed schools, bringing the total to 12 states and the District. Iconic events including the Masters golf tournament and the Boston Marathon were canceled. A rash of panic buying emptied shelves nationwide as people hoarded frozen food, toilet paper, bottled water and cleaning products for what some expect could be lengthy isolation within homes from coast to coast.

There are now more than 2,100 confirmed cases of covid-19, the disease caused by the virus, across the country, with reports in nearly every state. Forty-eight deaths in the United States have been linked to the virus, 25 of them in the Life Care Center of Kirkland nursing home in suburban Seattle, including three announced Friday. Health officials in Kansas said Friday that an elderly man who died this week of coronavirus was a resident of the Life Care Centers of America facility in Kansas City, Kan.

The national strategy for battling the coronavirus has shifted dramatically in the past 48 hours: It was a public health crisis for weeks, a societal disruption in recent days and only became an official national emergency on Friday afternoon. Strategies to combat its spread have been applied in a patchwork way, with some communities and states far more aggressive in closing workplaces and pushing for social distancing, while others have done next to nothing.

Shutdown America came as a recognition that the nation’s earlier, disparate strategies could not block the virus at the border or bottle it up in the places where it initially seeded. It signaled a national resignation that the virus has taken hold and hijacked normalcy, replacing it with fear and uncertainty.

“Thinking you are going to escape coming in contact with this, it’s not going to happen,” New York Gov. Andrew M. Cuomo (D) said Friday. One of his daughters had been in a precautionary 14-day quarantine due to possible exposure. “I understand fully the anxiety of people … but you can’t control it. Who knows where the cabdriver was, who knows where the person who sits next to you on the bus was, who knows who your buddy was with last night?”

“I don’t think this is going to be a short-term issue,” Cuomo said. “I think this could be a six, seven, eight, nine-month affair.”

As the closures accelerated Friday, San Jose Mayor Sam Liccardo blamed the national shortage of test kits, a complaint that has emerged in several jurisdictions.

“In the absence of adequate resources in the U.S. for testing that would enable local communities to mitigate the spread of covid-19, we are left with little choice but to shut schools and manage as best we can the very substantial disruption to our families and communities,” Liccardo said.

The strategic shift toward trying to impede the virus through social distancing is a calculated, if highly disruptive, attempt to slow down its spread by limiting the potential chains of transmission: people closely interacting with other people. The United States remains in the early stages of its fight with the virus and is now trying to keep sick and infected people from passing it on to those who are healthy, or at least to slow the transmissions enough to prevent a crush on the public health system.

Governors of numerous states, including California, Ohio and New York, have barred large-scale gatherings, as have officials in Washington state. Officials in Santa Clara County, Calif., on Friday announced even more restrictive rules, banning gatherings of more than 100 people and decreeing that whenever 35 people get together, they must have at least six feet of distance from others.

The vast retreat into homes has occurred in spotty fashion. Major cities, including Washington D.C., San Francisco and Los Angeles, have seen workplaces closing and employees telecommuting. But many employees, including those in low-wage service-sector jobs, must still show up at work to get paid.

Two of America’s most iconic places: Broadway and Disney World, are closed, but nightlife in places like New Orleans has continued unabated. In Florida, where some 5 million people are over the age of 60 and potentially vulnerable to a more serious covid-19 illness, many seniors this week continued their normal routines, including dance parties.

“The best thing we can do now to try to get through a very tough period is to try to slow the passage from one person to the next so that we don’t overwhelm our health-care system,” Francis Collins, the director of the National Institutes of Health, said in an interview Friday.

Collins said he is “very worried” about the virus and warned that if no action is taken the United States could end up like Northern Italy, where covid-19 is spreading unabated, more than 1,000 people have died and doctors are making unfathomable choices about who lives and dies.

“We have all been saying for years, maybe decades, that we were overdue for this kind of pandemic coming from somewhere with some kind of virus, so we should not be shocked and surprised that the time has come,” Collins said.

President Trump held a news conference on the coronavirus on March 13 in the Rose Garden, declaring a national emergency. (The Washington Post)

What happens next depends on how robustly the public health systems can respond to the crisis. Hospitals typically operate at nearly full capacity, even without a major contagion. This pandemic will test the ability of thousands of hospitals and medical facilities to handle a surge of critical cases.

Some public health leaders are urging the government to take aggressive steps to help people who feel they have to go to work even if sick.

“There are huge equity issues here. There are millions of people in America who are unable to stop working if they’re sick,” said Richard Besser, president and CEO of the Robert Wood Johnson Foundation and a former acting director of the Centers for Disease Control and Prevention. “We don’t want to force people to choose between paying the rent, putting food on the table and protecting their health and the health of others.”

Dez Phil, a 49-year-old flight attendant heading into a supermarket in the Bronx, said he now worries more about catching the coronavirus on the street then he does when he’s flying.

“There was no guidance and now everyone is just trying to do what they think is right, but now you can’t contain it,” he said, noting that the closures of Broadway and Disney mean restaurants don’t have people in them and tourism declines — an impact he can see. “I think people are less concerned about the virus and more concerned about the financial impact of not having a job.”

As the coronavirus continues to spread, phrases like “quarantine,” “isolation” and “social distancing” are making news. Here are the key differences of each. (The Washington Post)

New York saw its number of coronavirus cases in the state grow by 96 in just one day. The state now has 421 confirmed cases, including 154 in New York City. Cuomo said he is expecting thousands of cases to be confirmed in coming weeks. He worries that the state’s hospital capacity will become overwhelmed, and non-urgent surgeries will be postponed.

“It was here before you knew it, it was wider spread in the past than you know, and it will spread more than you think,” Cuomo said. “Nobody is going to be immune from this.”

Many people who are sick and seeking to be tested for the coronavirus have been turned away because they don’t meet strict testing criteria. Officials announced Friday that there will be drive-through testing facilities opening in New Rochelle, N.Y., which is seeing one of the worst outbreaks in the nation, and San Antonio, where cruise ship evacuees were transferred to a nearby Air Force base.

In California, routines were being scrambled by a cascade of closures. More than 670,000 students will stay home in Los Angeles. To compensate, the district said it would open dozens of “family resource centers” where children will be able to get meals and parents can get a break from child care.

San Diego, which has the state’s second-largest school district, also is shutting schools. In a joint statement, the leaders of the two districts acknowledged that efforts to stop the virus from entering their communities had failed and that a fresh approach is needed.

“California has now entered a critical new phase in the fight to stop the spread of the covid-19 pandemic,” wrote L.A. superintendent Austin Beutner and San Diego superintendent Paul Gothold. “There is evidence the virus is already present in the communities we serve, and our efforts now must be aimed at preventing its spread.”

Some state health officials said they were angry that the CDC provided detailed guidance on when to close schools just on Thursday afternoon.

Short-term closure of schools during the early stages of a spreading disease is unlikely to stem the problem, according to the guidance. Instead, it causes significant disruption for families, schools and those who might be responding to outbreaks in health-care settings. The CDC also said it could increase the impact on older adults who care for grandchildren and for children whose parents and family members are hourly and low-wage workers. Other options include staggering recess and canceling assemblies.

Longer closures, such as four weeks, could result in more students gathering outside of school and increase the risk to older adults or others who are more vulnerable, including those with underlying medical conditions.

“It’s not necessary to take aggressive actions in areas where there isn’t spread of this virus or there’s not been sustained community spread,” said one federal official involved in the response, who spoke on the condition of anonymity to speak candidly.

But for many state and local officials, decisions are often made that are based on more than just CDC guidance.

“You have to look at what is happening to us locally,” said Michael Fraser, chief executive of ASTHO, the association that represents state health directors. “Parental pressure to close is extremely high. Folks are so worried.”

Others seem to be taking the mammoth disruptions more in stride. Scott Sleigh, a 47-year-old project manager from Santa Clara, Calif., said he had been teleworking for the past week — and expected to do so for several more. He also had to cancel a trip to Disneyland after the theme park said Thursday it would be temporarily shutting down.

That’s inconvenient, he said while shopping at a Walmart in Santa Clara, but it’s for a greater good.

“They’re trying to prevent the spread,” he said.

Craig reported from New York. Annie Gowen in Kansas City, Kan., Arelis R. Hernández in San Antonio, Griff Witte in San Francisco and William Wan contributed to this report.