A global pandemic of the novel coronavirus has now killed at least 9,683 people in the United States.
The U.S. is, by far, the hardest-hit country with more than 338,900 diagnosed cases of COVID-19, the disease caused by the new respiratory virus, according to data compiled by the Center for Systems Science and Engineering at Johns Hopkins University.
More than 1.2 million people around the world have been diagnosed with coronavirus. The actual numbers are believed to be much higher due to testing shortages, many unreported cases and suspicions that some governments are hiding the scope of their nations' outbreaks.
More than 70,700 around the world have died, according to Johns Hopkins University's count.
Italy still has the highest death toll in the world — over 15,000.
Today's biggest developments:
Here's how the story is developing today. All times Eastern. Please refresh this page for updates.
In New York -- the state hit hardest by the pandemic -- the death toll has reached 4,758, Gov. Andrew Cuomo said Monday, though he said the rate of death has been "effectively flat for two days."
New York has the highest death toll in the U.S. by far. New Jersey has the second highest death toll with 917, said Cuomo.
More than 130,000 people in New York state have been diagnosed with the coronavirus.
Cuomo said the total number of hospitalizations, ICU admissions and daily intubations are down, which "suggest a possible flattening of the curve."
While New York may have reached the apex of coronavirus infections, the governor added, what happens next "still depends on what we do."
If the state is plateauing, it is because social distancing is working so that must continue, said Cuomo.
Also, the state's health care system "is at maximum capacity today," according to the governor. "The staff cannot work any harder. And staying at this level is problematic."
"There's also a real danger in getting overconfident too quickly. This is an enemy we have underestimated from day one and we have paid the price dearly," Cuomo said.
Schools and non essential businesses will remain closed until April 29, Cuomo said.
Cuomo lectured those who congregated in New York City's squares and parks this weekend and said he's increasing the maximum fine to $1000 for violating the social distancing protocol.
"Now is not the time to be lax. It is a mistake," the governor said.
"If I can't convince you to show discipline for yourself," Cuomo said, then do it for others, like the health care workers "putting their lives on the line."
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.
At least 5,373 patients in the United Kingdom have died from the coronavirus, as of Sunday night. That marks an increase of 439 deaths in 24 hours, according to the Department of Health and Social Care.
Over 51,000 people in the United Kingdom have tested positive for COVID-19, including Prime Minister Boris Johnson and Prince Charles, heir to the British throne.
The Masters plans to reschedule 2020's April tournament for Nov. 9 to 15.
"We want to emphasize that our future plans are incumbent upon favorable counsel and direction from health officials," Fred Ridley, chairman of Augusta National Golf Club, said in a statement Monday. "Provided that occurs and we can conduct the 2020 Masters, we intend to invite those professionals and amateurs who would have qualified for our original April date and welcome all existing ticket holders to enjoy the excitement of Masters week."
The novel coronavirus outbreak in Spain appears to be slowing down as the number of new infections drops in "almost all regions," a health ministry official said.
"The growth rate of the pandemic is decreasing in almost all regions," Maria Jose Sierra, with the Spanish Ministry of Health's emergency committee, said in a virtual press briefing Monday.
Sierra cautioned that it will take a few days to "confirm this tendency."
Monday's data from the Spanish health ministry shows that 637 people died from COVID-19 in the past 24 hours -- the lowest daily toll, percentage-wise, since early March -- bringing the nationwide death toll to 13,055. The country also reported 4,273 new cases, bringing the nationwide total to 135,032.
Spain has the second-highest national tally of diagnosed COVID-19 cases in the world, behind the United States, according to a count kept by Johns Hopkins University.
Sierra said around 19,400 health workers in Spain have been infected with the novel coronavirus, accounting for nearly 15% of the total number of cases.
Over the weekend, Spanish Prime Minister Pedro Sanchez announced that he would ask parliament to extend the country's state of emergency by two more weeks, taking the lockdown on mobility until April 26.
"Flattening the curve was our first objective. We’re getting close. But I ask everyone for sacrifice and resistance," Sanchez said in a televised address. "The next objective is to reduce infections even more until the number of new contagions is lower than the number of people recovering each day."
U.K. Prime Minister Boris Johnson, who was hospitalized Sunday night after contracting the novel coronavirus, said he went for "some routine tests" as his symptoms persisted.
"Last night, on the advice of my doctor, I went into hospital for some routine tests as I’m still experiencing coronavirus symptoms," Johnson said on Monday via Twitter. "I’m in good spirits and keeping in touch with my team, as we work together to fight this virus and keep everyone safe."
A spokesman for the prime minister's office announced in a statement on Sunday night that Johnson, 55, had a high fever and was admitted to a London hospital on the advice of his doctor, not in an emergency.
"This is a precautionary step," the spokesman said, "as the prime minister continues to have persistent symptoms of coronavirus ten days after testing positive for the virus."
Johnson will remain in contact with other British leaders while he awaits the results of his tests, according to the spokesman.
What to know about coronavirus:
Adm. Brett Giroir, assistant secretary for health at the U.S. Department of Health and Human Services, warned Americans that this will be the "peak week" of the novel coronavirus outbreak for some states and cities.
"For parts of the country, particularly New York, New Jersey, Connecticut, Detroit, this week is going to be the peak week," Giroir told ABC News chief anchor George Stephanopoulos in an interview Monday on "Good Morning America."
"It's going to be the peak hospitalization, peak ICU week and, unfortunately, peak death week," he added. "But that doesn't mean we're over this week. There are other parts of the country that will peak a little bit later, like New Orleans. So we have to be very, very serious about what's happening this week, next week, the following weeks -- do the physical distancing, wear the masks, that's how we're going to defeat this virus."
Giroir, a medical doctor and a key member of the White House coronavirus task force, said the country has "come a long way" in ramping up its COVID-19 testing capacity.
"As of yesterday we've conducted at least 1.67 million tests, and we don't even get information from all of the laboratory-derived tests. These are the ones that are in the hospitals that don't really report up through the system," he said. "We'll do about a million tests this week, and that's plenty enough tests for the people who really need it in the priority groups -- those who are hospitalized, health care workers, elderly."
Giroir said they are also working on scaling up serologic testing, more commonly known as an antibody test, which only requires a drop of blood and sniffs out virus antibodies. The test can't detect whether an individual presently has the virus, but it can tell if they already had it or had been exposed to it at some point in the past because their immune system has developed antibodies to fight it.
"That's very important as we think about reopening the country and the economy," Giroir said, "because if you have had the virus and you have an immune response to it, in all probability you are immune and safe from the virus."
Giroir said he's "very optimistic" that the country will soon have "tens of millions" of serologic tests, potentially by May.
"There are several that are going through the FDA right now," he added.
Japanese Prime Minister Shinzo Abe said he intends to declare a state of emergency over the country's novel coronavirus outbreak amid a recent surge in infections.
During a press conference Monday, Abe said he was making final arrangements for the declaration and would announce it as soon as Tuesday. The order would last for about a month and would apply to seven prefectures that includes major cities such as Tokyo, which has seen a jump in new infections in recent days.
The extent of the emergency measures were not fully known Monday, but the declaration would give prefectural governors the power to ask people to stay home. Local media reports say public transportation and supermarkets would remain open.
As of Monday, at least 3,654 people in Japan have been diagnosed with COVID-19 and 85 of them have died, according to a count kept by Johns Hopkins University.
The Japanese government has admitted that infection routes cannot be traced in an increasing number of cases.
The U.S. Embassy in Tokyo issued a stark warning to Americans in Japan on Friday, saying those who wish to return should do so now or risk being stuck there "for an indefinite period."
"For U.S. citizens now in Japan, if you plan to return to the United States, we recommend that you arrange for an immediate departure. Failure to do so could mean staying abroad for an indefinite period," the embassy said in the alert. "As compared to the number of positive cases and hospitalizations in the United States and Europe, the number of reported COVID-19 cases in Japan remains relatively low. The Japanese Government’s decision to not test broadly makes it difficult to accurately assess the COVID-19 prevalence rate."
3 a.m.: US Forces Japan declares public health emergency
The commander of the United States Forces Japan on Monday announced a public health emergency for the Kanto Plain "due to the steady increase" of novel coronavirus infections in nearby Tokyo.
The declaration, which will remain in effect through May 5, gives commanders the authority to enforce compliance of health protection measures on those who live and work on all U.S. Army, Navy, Air Force and Marine installations and facilities located on the Kanto Plain, the largest lowland in Japan that covers more than half of the eastern Kanto region, including Tokyo.
"Protecting the health and safety of everyone associated with U.S. Forces Japan is my number one priority," Lt. Gen. Kevin Schneider, U.S. Forces Japan commander, said in a statement Monday. "I cannot underscore enough the importance of personal responsibility at a time like this. Stopping the spread of COVID-19 requires the entire team -- service members, civilians, families, and our Japanese partners."
The announcement comes as the daily count of new COVID-19 cases in the Japanese capital have jumped in recent days, from 78 on March 31 to 143 on Sunday, according to data published on the Tokyo Metropolitan Government's website.
Last month, an active duty member of the U.S. Forces Japan tested positive for COVID-19.
In total, 1,033 people have tested positive for the disease in Tokyo and 30 of them have died, according to the government's website. A count kept by Johns Hopkins University show's Japan's nationwide tally is up to 3,654 diagnosed cases and 85 deaths.
ABC News' Aicha El Hammar, Kelly McCarthy and Anthony Trotter contributed to this report.