WASHINGTON (AP) — Millions of Americans holed up at home against the coronavirus Monday, with many of them thrown out of work until further notice, as authorities tightened the epic clampdown and the list of businesses forced to close across the U.S. extended to restaurants, bars, gyms and casinos.

With the U.S. economy shuddering to a halt, the Dow Jones Industrial Average plummeted nearly 3,000 points, or 13%, its biggest one-day fall in decades.

The rapid work stoppage had Americans fretting about their jobs and their savings, threatened to overwhelm unemployment benefit programs, and heightened fears the U.S. is sliding into recession.

The number of infections in the U.S. climbed to about 3,800, with at least 70 deaths, nearly two-thirds of them in hard-hit Washington state.

Officials in six San Francisco Bay Area counties issued a "shelter-in-place" order affecting nearly 7 million people, requiring most residents to stay inside and venture out only for necessities for three weeks — the most drastic measure taken yet in the U.S. to curb the spread of the virus.

"The most important thing you can do is remain home as much as possible," San Francisco Mayor London Breed said on Twitter. "There is no need to rush out for food or supplies, as these stores will remain open."

The shutdowns touched every corner of the country: blackjack dealers in Las Vegas, theme park workers in Orlando, Florida, restaurant and bar employees nationwide, and winery workers in California. At least eight states called on all bars and restaurants to close at least part of the day. Casinos shut down ed in New Jersey.

Tyler Baldwin, a 29-year-old bartender at the Taproom in Seattle's Pike Place Market, one of the city's biggest tourist attractions, shut down early "so I can go home and start figuring out unemployment, food stamps, really whatever the next step to keep myself afloat."

Truckers hauling goods from a port in Virginia are losing two to three days of work each week and just trying to hang on because cargo volume has dropped so much.

"It's a struggle just to survive right now, just to put food on the table," said Nicole Sapienza, managing member of Coastwide Marine Services in Virginia.

About 82 million people, or three-fifths of the U.S. workforce, are hourly employees. Many of them won't get paid if they don't work. For those in a category that includes restaurant, hotel, amusement park, and casino workers, just one-third have access to paid sick leave, according to Wells Fargo.

Kevin Hassett, a former economic adviser to President Donald Trump, said on CNN that "that the odds of a global recession are close to 100% right now" and predicted the U.S. could lose about 1 million jobs in April.

"If that happens you're looking at one of the biggest negative jobs numbers that we've ever seen," he said. "Now, of course, that would hopefully reverse itself quickly if we get ahead of the curve on this."

The economy appears to be decelerating at a much faster pace than in the 2008 financial crisis. If Hassett's forecast of job losses is accurate, that would be just two months after the government reported a healthy gain of 273,000 jobs.

"This is like an avalanche, it's all happening at once," said Heidi Shierholz, senior economist at the Economic Policy Institute. "And no one knows how long it's going to last."

With schools shut down for tens of millions of children, parents began using plans that included such as flash cards, online learning, dog walks and creativity sessions. Many did this while juggling work conference calls, emails and memos. Others scrambled to find child care.

Mathews Schroder was about to begin work as a host at SeaWorld Orlando but was notified that his start would be pushed back because of the shutdown of the resort area's major theme parks.

"I don't know when my next meal is going to be. I'm going to have to collect unemployment until I get notification about when I start," Schroder said. Luckily, he can get health insurance through his wife's job at a Taco Bell.

The shutdowns were especially devastating for the many artists and service industry workers in New York who rely on nightlife and live paycheck to paycheck with meager benefits in one of the most expensive cities in the world.

Ralph Anthony, a comic and actor in New York City, had two gigs canceled last week that cost him $1,000 — money he intended to use to pay next month's bills.

"There's literally no work to go around," said Anthony, 38. "You're living off your savings. You're liquidating your investment portfolio."

In a letter to President Donald Trump and congressional leaders, the U.S. Chamber of Commerce called for swift legislation, including a three-month cancellation of some taxes and an expansion of loans to businesses, to "mitigate the potentially devastating economic effects."

Governors in a number of states said they are growing increasingly alarmed by the widening economic damage and the effect on workers. Some announced changes to make it easier for people to collect unemployment benefits. Others accelerated programs to make loans available to more small businesses.

Yet some analysts worry that unemployment benefit systems could be overwhelmed by a flood of people seeking aid. In January 2009, at the height of the Great Recession, many online and phone systems for filing requests for unemployment crashed.

In fact, the website where businesses could apply for Small Business Administration disaster loans crashed Monday.

The U.S. surgeon general, meanwhile, said the number of coronavirus cases in the United States has reached a level comparable to what disease-battered Italy recorded two weeks ago — a signal that infections are expected to rise in America. Italy is reporting an estimated 25,000 cases and more than 1,800 deaths.

"We are at a critical inflection point in this country, people," Surgeon General Dr. Jerome Adams told Fox News. "When you look at the projections, there's every chance that we could be Italy."

A healthy volunteer became the first participant in a clinical trial of an experimental vaccine against the virus, receiving a dose at a research institute in Washington state. Public officials cautioned, however, that it will still take a year to 18 months to fully test and approve any vaccine.

Across the country, health officials, politicians and business leaders talked about "social distancing" and "flattening the curve," or encouraging people to avoid others so as to slow the spread of the virus and keep U.S. hospitals from being overwhelmed with a sudden deluge of patients.

Most people who come down with the disease have relatively mild symptoms, but it can be deadly for some, especially the elderly and those with underlying health problems. Most people infected with the virus recover in a matter of weeks.

Around the country, people had to figure out how entertain themselves now that nearly all social gatherings have been banned, canceled or strongly discouraged. Some people planned to binge-watch TV, catch up on chores such as cleaning out the basement, exercise at home, do more cooking or read.

"We're catching up on our reading. I just started `Love in the Time of Cholera.' It seemed appropriate," said Beverly Pfeiffer in Silver Spring, Maryland, of the Gabriel Garcia Marquez classic.

The worldwide outbreak has sickened nearly 175,000 people and left more than 6,500 dead, with thousands of new cases each day.