Coronavirus Live Updates: Saudi Arabia, Leaders Ailing, Declares Cease-Fire in Yemen

Asked about Mr. Trump’s comments on Wednesday, Dr. Tedros Adhanom Ghebreyesus, the W.H.O. director-general, said, “We want to learn from our mistakes,” but added, “for now, the focus should be on fighting this virus.”

“Please don’t politicize this virus,” Dr. Tedros said. “If you want to be exploited and you want to have many more body bags, then you do it. If you don’t want many more body bags, then you refrain from politicizing it.”

He emphasized that the disease was new, adding, “there are many unknowns and we don’t know how it will behave in future.”

While some critics have called on Dr. Tedros to resign, he said he was not deterred and could withstand “three years” or “three hundred years” of personal attacks. He did not cite Mr. Trump by name.

He said for the first time that for months he has been targeted by racist comments and death threats.

In Japan, the deputy prime minister and finance minister, Taro Aso, recently noted that some people referred to the W.H.O. as the “Chinese Health Organization” because of what he called its close ties to Beijing.

Taiwan officials say the W.H.O. ignored their early warnings about the virus because China refuses to allow Taiwan, a self-governing island that Beijing claims as its territory, to become a member.

In just a few months, more than two dozen companies have announced promising vaccine programs aimed at ending the pandemic, speeding through the early stages of testing unlike ever before.

On Wednesday, Novavax, a Maryland-based biotech company, said its vaccine candidate had stimulated a powerful immune response in lab and animal experiments, producing antibodies that could fight off the coronavirus. The vaccine, called NVX-CoV2373, is set to begin human trials in Australia in mid-May. A final product that would be widely available is still a year or more away.

“We’re all trying to do something which we have almost no precedents for, which is accelerating a vaccine in the middle of a pandemic,” said Dr. Peter Hotez, who is a co-director of the Texas Children’s Hospital Center for Vaccine Development at Baylor College of Medicine.

But the Chinese city of Wuhan, where the coronavirus pandemic started, lifted its lockdown on Wednesday, allowing 11 million residents to leave the city without special authorization for the first time in more than 10 weeks.

But virologists and public health officials say that easing restrictions too swiftly could produce the catastrophic scenario that the lockdowns have so far kept at bay.

Prime Minister Boris Johnson of Britain is stable and “responding to treatment” for the coronavirus, but remains in intensive care, a spokesman said on Wednesday.

Downing Street declined on Wednesday to comment on what treatment Mr. Johnson was receiving, though it repeated previous statements that he is breathing without assistance apart from receiving oxygen.

The office said he was in good spirits but made clear that Foreign Secretary Dominic Raab, initially asked to stand in for Mr. Johnson “where necessary,” was now doing so full-time. The prime minister can speak with people when necessary, but is not working.

Mr. Raab is already serving as chairman of a key committee on the pandemic, as the government works to control the epidemic and stabilize an economy hit hard by the lockdown measures it has imposed.

The 16-hour meeting was meant to produce recommendations for collective action by the 19 European Union nations that use the euro, in addition to policies enacted by individual countries. While there was broad support for some ideas, like a $109 billion fund for unemployment benefits, others proved more contentious.

Analysts foresee the worst recession in generations — a roughly 13 percent economic contraction across the 19 European Union nations that share the euro.

The European Union’s top scientist quit after failing to persuade his superiors to create a major scientific program to confront the virus. Colleagues said he had been asked to leave.

Dr. Mauro Ferrari, who became president of the European Research Council in January, resigned on Tuesday in a letter to Ursula von der Leyen, the European Commission president.

“I have been extremely disappointed by the European response to Covid-19,” he said in a statement to The Financial Times. “I arrived at the E.R.C. a fervent supporter of the E.U.,’’ he wrote, but “the Covid-19 crisis completely changed my views.”

Dr. Ferrari said he began to press for a special virus program in early March, but it was barred by the bloc’s rules. He said he worked with Ms. von der Leyen on an alternative, but it was apparently blocked by the commission’s bureaucracy.

On Wednesday, the Research Council rejected Dr. Ferrari’s version of events, saying he had been forced out in part because he spent half his time in the United States and missed important meetings.

Senator Bernie Sanders of Vermont announced on Wednesday that he was dropping out of the Democratic presidential race. Mr. Sanders had spent the last several weeks on the sidelines, while facing calls from fellow Democrats to exit the race and help unify the party behind former Vice President Joseph R. Biden Jr.

And in a grim signal of the crisis faced by the nation, New York State now has more confirmed cases than either hard-hit Spain or Italy, and has more cases than any single country in the world outside of the United States.

In Washington, Democratic leaders said on Wednesday that they would push to double the size of a $250 billion emergency measure requested by the Trump administration this week for loans to distressed businesses, adding money for hospitals, states and food aid.

The request could slow what the White House and Republican congressional leaders said they hoped would be quick passage by week’s end of an interim relief package to supplement the $2 trillion stimulus law enacted last month.

Across the United States, the death toll surpassed 14,000, about half of them in New York and New Jersey. Among the latest deaths announced was John Prine, 73, an American country-folk singer who died on Tuesday in Nashville.

In those countries, large numbers of working-age people live with their parents, and the younger people may be bringing the virus home and spreading it to their far more vulnerable, elderly parents.

Some economists have challenged the rigor and validity of that analysis, and the argument is unfolding just as armchair epidemiologists and self-appointed anthropologists indulge cultural stereotypes to speculate on matters of grave import. Some claim that Japan has seen fewer deaths because people bow rather than shake hands.

In Italy and Spain, a cultural tendency toward intergenerational living was reinforced by an economic catastrophe that forced legions of jobless people to take refuge with their parents. In the decade after the global financial crisis of 2008, the share of Italians between the ages of 25 and 29 who were living with their parents rose to 67 percent from 61 percent, according to Eurostat. In Spain, the same cohort expanded to 63 percent from 51 percent.

Italy and Spain have far more officially recognized coronavirus deaths than any other countries — more than 32,000 between them.

Bodies left out on sidewalks. The authorities struggling to keep track of deaths. Funeral parlors, out of coffins, using cardboard boxes made by companies that usually package bananas and shrimp.

The calamity unfolding in Ecuador’s business capital, Guayaquil, offers an ominous look at how officials’ ability to respond to the coronavirus pandemic in Latin America can be dangerously hamstrung by the inequality, weak public services and fragile economies that mark much of the region.

“What we’re seeing in Guayaquil is what can happen in most of South America’s large cities, where pockets of cosmopolitan richness coexist with widespread poverty,” said Alexandra Moncada, who directs activities in Ecuador for the international aid organization CARE.

Ecuador’s president, Lenín Moreno, has warned that the real figure is much higher, but that because testing is limited, the true extent of infections is impossible to determine.

It is still unclear why the country has been affected so deeply. Some experts believe the virus may have traveled along the country’s deep migratory links with hard-hit Spain and Italy, then spread as Ecuador lagged in adopting social distancing measures.

Mask shortages in hospitals. Inadequate diagnostic testing. Medical supplies flown in from overseas. And an international charity setting up a field hospital in Central Park.

“Africa just felt better,” said John Shaw, who has lived for two years in Nairobi, Kenya, with his wife and two sons. “There are a lot of unknowns in terms of how Americans will deal with this crisis. It didn’t feel obvious to us at all that it will go well there.”

As the pandemic spreads and infections increase across the world, many Americans working or studying abroad have returned home. U.S. embassies organized evacuation flights for citizens seeking to flee countries that have long been criticized for shabby health care systems and government misinformation.

The virus has been slow to take hold in many parts of Africa, but as confirmed infections and deaths climb, the continent’s readiness to deal with a pandemic is being questioned. On Tuesday, the World Health Organization said the number of cases across the continent had risen to more than 10,000, with more than 500 deaths.

The United States has reported a vastly higher number — at least 397,000 cases, the highest tally worldwide. With the health care system fraying and the economy faltering, some American citizens — especially those living abroad — are starting to see their country in a new, unsettling light.

Seismometers may be built to detect earthquakes, but their mechanical ears hear much more. Even the everyday hum of humanity — people moving about on cars, trains and planes — has a seismically detectable heartbeat.

But as billions of people have been instructed to stay home to curtail the pandemic’s spread, the roar of urban life has turned into a whisper all over the world. Today, in cities large and small, the thumping pulse of civilization is now barely detectable on seismograms.

With seismometers, Ms. Labedz said, you can see the collective willingness of millions of the world’s urban dwellers to hunker down.

Scientists are now able to better hear the planet’s natural tectonic soundtrack.

“We can detect smaller earthquakes, just like how it’s easier to hear a phone ring in a library than at a rock concert,” Ms. Labedz said.

One result is the emergence of something rare: a pure blue sky.

“I don’t know how long this will last,” said Sudhir Kumar Bose, a retired English professor in New Delhi, the capital. “But right now I feel much better.”

Those clear skies might do more than just lift people’s moods.

Multiple studies have found that exposure to fine particulate matter puts people at heightened risk for lung cancer, heart attacks, strokes and even premature death. But a new study by Harvard University researchers — the first of its kind in the United States — shows a statistical link between dirty air and death or serious illness from Covid-19, the disease caused by the new coronavirus.

In an analysis of 3,080 U.S. counties, the study’s authors found that a slight increase in long-term pollution exposure could have serious coronavirus-related consequences, even accounting for other factors like smoking rates and population density. A person living for decades in a county with high levels of fine particulate matter, for example, was 15 percent more likely to die from the virus than someone in a region with slightly less air pollution.

“Most countries don’t take it seriously enough and aren’t doing enough given the scale of the harm that air pollution is doing to all of our health,” said Beth Gardiner, a journalist and the author of a book on the subject.

Their work is more perilous than ever. On Wednesday, Britain marked its highest single day death toll, nearly 1,000 people, bringing the total number of deaths to more than 7,000.

Dr. Adil el-Tayar, 64, originally from Sudan, was among the first doctors to die from the coronavirus in Britain. His cousin, Dr. Hisham el-Khidir, said better protective gear and screening protocols could have saved him.

“In our morbidity analyses, we go through each and every case and ask, ‘Was it preventable? Was it avoidable?’” he said. “Even with all the difficulties, I’ve got to say the answer has to be yes.”

For months, the Chinese government’s propaganda machine had been fending off criticism of Beijing’s handling of the coronavirus outbreak, and it finally seemed to be finding an audience. Voices as varied as the World Health Organization, the Serbian government and the rapper Cardi B hailed China’s approach as decisive and responsible.

But China could not savor the praise for long. In recent days, foreign leaders — even in friendly nations like Iran — have questioned China’s reported infections and deaths. A top European diplomat warned that aid from Beijing was a mask for its geopolitical ambitions, while a Brazilian official suggested the pandemic was part of a plan to “dominate the world.”

China’s critics, including the Trump administration, have accused the Communist Party’s authoritarian leadership of exacerbating the outbreak by initially trying to conceal it. But China is trying to rewrite its role, leveraging its increasingly sophisticated global propaganda machine to cast itself as the munificent, responsible leader that triumphed where others have stumbled.

What narrative prevails has implications far beyond an international blame game. When the outbreak subsides, governments worldwide will confront crippled economies, unknown death tolls and a profound loss of trust among their people. Whether Beijing can step into that void, or is pilloried for it, may determine the fate of its ambitions for global leadership.

Claims that the virus is a foreign bioweapon, a partisan invention or part of a plot to re-engineer the population have replaced a mindless virus with more familiar, comprehensible villains. Each claim seems to give a senseless tragedy some degree of meaning, however dark.

The belief that one is privy to forbidden knowledge offers feelings of certainty and control, psychologists say, and sharing that information may give people a sense of agency during a crisis that has turned the world upside down.

Rumors and baseless claims are spread by people whose critical faculties have simply been overwhelmed by feelings of confusion and helplessness, experts warn. But false claims are also being promoted by governments looking to hide their failures, partisan actors seeking political benefit, run-of-the-mill scammers and, in the United States, a president who has pushed unproven cures and blame-deflecting falsehoods.

They have led people to consume fatal home remedies and flout social distancing guidance. And they are disrupting the sweeping collective actions, like staying at home or wearing masks, needed to contain the virus.

“We haven’t faced a pandemic at a time when humans are as connected and have as much access to information as they do now,” said Graham Brookie, who directs the Atlantic Council’s Digital Forensic Research Lab.