Everyone in UK must stay home to fight coronavirus, prime minister says More than 372,000 around the world have been diagnosed with the coronavirus.

At least 573 people have now died in the United States from the novel coronavirus -- and officials say the pandemic is accelerating.

In the United States, there are more than 41,700 diagnosed cases of the disease caused by the new respiratory virus, known officially as COVID-19, according to data compiled by the Center for Systems Science and Engineering at Johns Hopkins University.

The coronavirus spans every U.S. state as well as Washington, D.C., and Puerto Rico, forcing millions of Americans to stay home in an effort to contain the disease.

Over 372,000 people around the world have been diagnosed and more than 16,300 people have died across the globe, mostly in Italy and China.

Monday's biggest developments:

Everyone in UK must stay home

The pandemic is 'accelerating,' WHO director-general says

Diagnosed cases soar to over 20,000 in New York

Amy Klobuchar's husband tests positive for coronavirus

Here's how the news developed Monday. All times Eastern.

11:46 p.m.: Effects of virus felt by Minnesota's top officials

Minnesota Governor Tim Walz announced that he is in self-quarantine after a member of his security detail tested positive for the coronavirus.

Walz, who is the first U.S. governor to self-quarantine, will continue to run the state from his home in St. Paul. The 55-year-old said he is healthy and not showing any symptoms.

His disclosure came on the heels of Minnesota Sen. Amy Klobuchar's announcement that her husband was being hospitalized after contracting the virus.

On Sunday, Minnesota Lt. Gov. Peggy Flanagan announced that her brother, Ron, died from COVID-19 on Saturday. He had been fighting cancer at the time he contracted the virus, Flanagan said on Instagram.

"To many, he'll be a statistic," Flanagan said in the post. "But to me, I’ll remember a loving, older brother, uncle, father, and husband."

9:21 p.m.: Inmate in NYC detention center is latest to test positive

An inmate at a federal detention facility in New York City is the latest U.S. prisoner to test positive for the coronavirus.

Sources tell ABC News that an inmate at the Metropolitan Correctional Center in Lower Manhattan has tested positive for COVID-19. The inmate is currently being housed at a local hospital, sources say.

When reached about a possible case of COVID-19 at MCC New York, Tyrone Covington, president of union that represents the facility's officers and staff, said he was “outraged” it could be a possibility.

Over the weekend, three inmates in the Bureau of Prisons tested positive for the coronavirus: two in Oakdale, Louisiana, and one in Brooklyn, New York. Two other Bureau of Prisons staff members -- one in Kansas and one in Texas -- have tested positive for the virus.

Separately, sources say that one staff member and three inmates have tested positive in Atlanta, and eight inmates and staff await test results in Yazoo, Mississippi.

7:28 p.m.: Flights worldwide down by half, says flight data service

As airlines continue to eliminate flights in response to governmental travel restrictions and plunging demand, an airline data-tracking service reports that the number of flights worldwide is down by half.

FlightAware says that as of this past Sunday, March 22, the overall decrease in worldwide commercial flight volume this year compared to last was 48%.

The airline industry could take a hit of up to $113 billion as a result of the coronavirus outbreak, according to industry experts.

5:45 p.m.: Florida gov. orders self-isolation for NY-area visitors

Florida Gov. Ron DeSantis announced an executive order that mandates anyone who travels to Florida from the greater New York City area will have to go into a 14-day self isolation period.

"Today, there's over 190 direct flight from the New York City area to the state of Florida. And I'd would reckon, given the outbreak there, that every single flight has somebody on it that is positive for COVID-19," he said in a news conference.

The order applies to anyone traveling to Florida from "an area with substantial community spread," but it specifically mentions New York, New Jersey and Connecticut.

Florida currently has about 1,100 positive cases and 14 deaths related to the virus. DeSantis has previously blamed visitors from New York for the cases in Florida and called on the White House to suspend flights from there and other states with a high number of outbreaks.

As of Monday morning, New York state had more than 15,000 coronavirus cases.

4:40 p.m.: Everyone in UK must stay home

Everyone in the United Kingdom "must stay at home," Prime Minister Boris Johnson announced Monday.

Residents can only leave the house to shop for basic necessities, for one form of exercise per day, for medical needs and to travel to and from work when absolutely necessary and working from home is not possible, Johnson said.

At least 6,724 people in the United Kingdom have been diagnosed with COVID-19 and more than 300 of those have died.

Gatherings outside the home of more than two people are now banned, the U.K. prime minister said.

Johnson said all unnecessary shops will close, as well as libraries and gyms. All social events must be canceled, including weddings, but excluding funerals, he said.

4:28 p.m.: Instacart plans to hire 300,000 more shoppers

As the demand for grocery delivery grows, Instacart says it plans to hire 300,000 more personal shoppers across North America over the next three months.

The company, which uses personal shoppers to fulfill orders for customers, also noted how the hiring initiative can help provide flexible job opportunities for those who need it.

Meanwhile, CVS said it's hiring 50,000 full and part-time employees nationwide.

Tune into ABC at 1 p.m. ET and ABC News Live at 4 p.m. ET every weekday for special coverage of the novel coronavirus with the full ABC News team, including the latest news, context and analysis.

3:14 p.m.: Criminal consequences possible for those who violate NJ rules

In New Jersey, where at least 27 people have died from coronavirus, those who violate social distancing rules or keep non-essential businesses open could face criminal consequences, said Gurbir Grewal, the state's attorney general.

"The time for warning is over," Grewal said Monday. "If you're a retail store or an entertainment center and you stay open, or if you're a bar and keep serving patrons in your establishment, consider this as your final warning. Your actions are against the law in New Jersey, and you will be held accountable/"

"The same goes for individuals," Grewal said. "If you and your friends decide to throw a party at your home and you invite 20 of your closest friends, stop. Law enforcement officers will have to break that party up, and their will be criminal consequences."

Over 2,800 people have been diagnosed with coronavirus in the Garden State.

3:03 p.m.: Rhode Island becomes 8th state to postpone presidential primary

Rhode Island Gov. Gina Raimondo says she will sign an executive order to move the state's presidential primary from April 28 to June 2.

The governor also said she will make the election predominantly vote-by-mail. Applications and stamps will be sent to voters in the coming weeks, added Rhode Island Secretary of State Nellie Gorbea.

Indiana, Connecticut, Louisiana, Georgia, Kentucky, Ohio and Maryland as well as Puerto Rico have all moved their primaries in the wake of the pandemic.

2:56 p.m.: Virginia schools closed until end of year, North Carolina schools shuttered until May 15

In Virginia, where there are 254 confirmed coronavirus cases, all schools will remain closed until the end of the academic year, Gov. Ralph Northam announced.

The state is working to provide meals to students in need, Northam said.

In North Carolina, all public K-12 schools will be closed until May 15, Gov. Roy Cooper said Monday.

The governor said he arrived at this date by looking at guidance from the Centers for Disease Control and Prevention (CDC) and public health officials. The order would be adjusted if guidance changes, he said.

1:55 p.m.: Over 6,000 dead in Italy

Italy, hardest hit by deaths from the pandemic, reported 601 more fatalities in the last 24 hours, bringing the country's total death toll to 6,077.

The total confirmed coronavirus cases in Italy has climbed to 63,927, according to the country's Civil Protection Agency.

12:08 p.m.: The pandemic is 'accelerating'

The coronavirus "pandemic is accelerating," World Health Organization (WHO) Director-General Dr. Tedros Adhanom Ghebreyesus warned Monday.

Almost every country in the world has reported cases, he announced in a Geneva press conference.

"It took 67 days from the first reported case to reach the first 100,000 cases. Eleven days for the second 100,000 and just four days for the third 100,000," he said.

11:50 a.m.: Non-essential businesses closing in Massachusetts, Maryland, Michigan

A stay-at-home advisory has been issued in Massachusetts, urging residents to avoid unnecessary travel from Tuesday until April 7.

Also beginning Tuesday, all "non-essential" businesses in Massachusetts will be closed, though Gov. Charlie Baker encouraged restaurants to continue to offer food for take-out and delivery.

In Maryland, where there are at least 288 diagnosed cases, all non-essential businesses must close by 5 p.m. Monday.

Maryland Gov. Larry Hogan said he is not issuing a shelter-in-place order or forcing people to stay home but noted that unless Maryland residents have a critical reason to leave their homes, they should stay put.

Michigan officials are also ordering the temporary closure of non-critical businesses. Residents must say in their homes unless going somewhere is necessary.

11:39 a.m.: Minnesota governor to self-quarantine

Minnesota Gov. Tim Walz said Monday morning he will self-quarantine after a member of his security detail tested positive for the coronavirus on Sunday night.

"I’m using this as an opportunity to lead by example," Walz said in a statement. "Though I’m feeling healthy and not showing any symptoms, I’m going to work from home and model the protocol we are asking all Minnesotans to follow."

11:16 a.m.: Diagnosed cases soar to over 20,000 in New York

In New York state, where diagnosed coronavirus cases have soared to over 20,000, New York Gov. Andrew Cuomo said testing is also on the rise, with 16,000 tests now conducted per day.

About 25% of testing nationwide is now in New York state, Cuomo said Monday.

Cuomo on Monday issued an emergency order to all hospitals requiring them to increase capacity by 50%, with a goal of increasing capacity by 100%. Four facilities in the state are being converted into hospitals.

Of those diagnosed in New York, 13% are hospitalized, the governor said. New York state has reported 157 deaths.

"We were not ready to deal with this. And other situations will happen," Cuomo said. "Let's at least learn from this to be prepared for the next situation, as dramatic as this one has been."

Cuomo once again got personal at Monday's news conference, saying a silver lining he's gained during the pandemic is the "beautiful gift" of more time with his daughter.

10:50 a.m.: Amy Klobuchar's husband tests positive for coronavirus

Former Democratic presidential candidate and Minnesota Sen. Amy Klobuchar says her husband, John Bessler, received positive coronavirus test results Monday morning.

Bessler suffered a bad cough, including coughing up blood, and now has pneumonia and is on oxygen but not a ventilator, Klobuchar said in a statement.

"He is exhausted and sick," she said.

Bessler waited five days for the test results, Klobuchar said on a press call with a vote-by-mail advocacy group.

"John and I have been in different places for the last two weeks and I am outside the 14-day period for getting sick, my doctor has advised me to not get a test," Klobuchar said. "As everyone is aware, there are test shortages for people who need them everywhere and I don’t qualify to get one under any standard."

"I love my husband so very much and not being able to be there at the hospital by his side is one of the hardest things about this disease," she wrote. "I hope he will be home soon. I know so many Americans are going through this and so much worse right now. So I hope and pray for you, just as I hope you will do for my husband. Meanwhile I am working in the Senate to get help to the American people."

What to know about coronavirus:

How it started and how to protect yourself: coronavirus explained

What to do if you have symptoms: coronavirus symptoms

Tracking the spread in the US and worldwide: coronavirus map

9:20 a.m.: New Jersey testing site reaches capacity before it opens

In northern New Jersey, hit hard by the outbreak, a testing site at Bergen County Community College reached capacity even before it opened Monday morning, reported ABC New York station WABC.

8:39 a.m.: Doctor's plea for supplies

A Massachusetts emergency room doctor, who made a sharp-worded appeal on Facebook for the need for protective gear, told ABC News he's since received a number of donated supplies.

"Since that post went out, people have been showing up in our ER, donating whatever they have, people have been making masks," Dr. Josh Lerner, who works at the Leominster campus of UMass Memorial HealthAlliance-Clinton Hospital, said in an interview Monday on "Good Morning America."

"People are dropping off food, any type of personal protective equipment. Painters, contractors are giving us their supplies. A neighbor of mine dropped off a box of N95 masks this morning, left it on my porch," Lerner continued. "So we are being heard by the American people."

But Lerner said it's unclear how long the supplies will last as his emergency room starts to see an influx in acute cases of patients sickened with the novel coronavirus disease.

"I think something to keep in mind is that, for any one patient, there are multiple health care workers who are at the bedside," he said. "We could be talking about many, many supplies being used at any one time at the bedside. And so, at this moment, I don't know how many more days of supplies we have, but we are sort of using them as judiciously as possible."

Lerner called on the U.S. government as well as leaders at the local, state and federal levels to "work together" rather than "debate with one another."

"We as an entire nation need to come together to fight this," he said.

7:48 a.m.: Spain reports 462 deaths in past 24 hours

Spain's health ministry on Monday reported 462 deaths from the novel coronavirus in the past 24 hours.

The country's death toll from COVID-19 has now topped 2,000. Spain has the third-highest number of recorded deaths in the outbreak, following China and Italy.

With over 33,000 diagnosed cases, Spain is behind the United States and Italy in the highest national total outside China.

5:39 a.m.: Wuhan, China, reports no new cases for 5 straight days

The Chinese city of Wuhan, the original epicenter of the novel coronavirus outbreak, has reported no new confirmed cases for the past five days.

The city is still considered a high-risk zone but signs of life are reappearing on the streets as authorities begin to relax some of the strict measures that were put in place. Road checkpoints are being removed and some private vehicles have returned to the streets. The city's subway system remains shut down but has begun trial runs as health workers disinfect the subway cars and stations.

City leaders met Monday to discuss scheduling the resumption of work and production. Monday marks two months since Chinese authorities placed Wuhan on lockdown as the virus spread like wildfire throughout the city and the greater Hubei province.

"The meeting emphasized the need to make overall plans to restore economic and social order, and actively and steadily promote orderly resumption of work and production," the Wuhan government said in a statement Monday. "It is necessary to speed up the resumption of production and industrial enterprises, the return of stores and supermarkets as soon as possible, the orderly restoration of public transportation, the safe and orderly movement of personnel, and the guarantee of resumption of production and market."

4:09 a.m.: Florida closes all state parks

Florida is closing all of its state parks to the public due to the coronavirus crisis.

At the direction of the governor and to successfully uphold social distancing guidance from the U.S. Centers of Disease Control and Prevention, the Florida Department of Environmental Protection said it will close all state parks to the public, effective Monday. The Sunshine State is home to nearly 200 state parks and trails.

A notice on the Florida State Parks website said the Department of Environmental Protection "has taken many measures to continue providing resource recreation at our state parks during this time, such as limiting operating hours and reducing visitor capacity at parks with high visitation."

"Unfortunately," the notice continued, "this has not resulted in the reductions needed to best protect public health and safety as Florida continues to mitigate the spread of COVID-19."

There are more than 1,000 diagnosed cases of the novel coronavirus in Florida, and at least 13 of those patients have died, according to data compiled by Johns Hopkins University's Center for Systems Science and Engineering.

3:42 a.m.: U.S. Secret Service employee tests positive

A U.S. Secret Service employee is in quarantine after testing positive for the novel coronavirus, the agency confirmed in a statement late Sunday night.

"The Secret Service has conducted a comprehensive contact trace assessment and determined that the employee has not had contact with any Secret Service employee or protectee for nearly three weeks," the agency said.

Further information about the employee's identity was not provided due to privacy considerations.

3:00 a.m.: Japan to begin quarantining all visitors from the US

Japanese Prime Minister Shinzo Abe announced Monday that his country will require a 14-day quarantine to all visitors from the U.S. amid an escalating number of coronavirus infections around the globe.

The quarantine requirement includes Japanese and American citizens and will go into effect Thursday until the end of April. The move comes after Japan raised its travel advisory for the U.S., urging Japanese citizens not to make nonessential trips to the nation.

Abe said the new requirement is in line with containment measures taken by other countries, including the United States, which has reported a surge in new COVID-19 cases in recent weeks.

3:00 a.m.: Plan for Olympics not yet decided

Japan appears to have successfully slowed the spread of the virus on its soil, with just 1,101 diagnosed cases as of Monday, according to data compiled by Johns Hopkins University's Center for Systems Science and Engineering.

Still, Abe said a decision to postpone the 2020 Summer Olympics in Tokyo, slated to kick off on July 24, "may become inevitable" if the pandemic makes it impossible to hold the event safety.

The International Olympic Committee’s executive board has announced a plan to analyze the situation over the next few weeks and make a decision that could include the option to postpone, although the board emphasized that it has no current plans to outright cancel the games. A number of Olympic athletes have called on organizers to postpone or cancel the games due to the pandemic.

“If it is difficult to hold in a complete way, a decision of postponement would be unavoidable,” Japan's prime minister said during a parliamentary session in Tokyo Monday.

ABC News' Clark Bentson, Aicha El Hammar, Rachel Katz, Alexander Malin, Phoebe Natanson, Kirit Radia, Olivia Rubin, Quinn Scanlan, Christine Theodorou, J Gabriel Ware, Ivan Pereira and Karson Yiu contributed to this report.