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President Trump’s medical team delivered an update on Sunday of his condition, as the president’s personal physician acknowledged delivering an overly rosy picture of his illness a day earlier to please his notoriously sensitive patient. The details of the briefing signaled to some health experts that the president’s condition might be more serious than a mild case of Covid-19.
“I didn’t want to give any information that might steer the course of illness in another direction, and in doing so, you know, it came off that we were trying to hide something, which wasn’t necessarily true,” Dr. Sean P. Conley, the White House physician, said in a briefing with reporters Sunday.
Based on the doctors’ account, Mr. Trump’s symptoms appear to have rapidly progressed since he announced early Friday morning that he had tested positive for the coronavirus.
Mr. Trump had a “high fever” on Friday, and there were two occasions when his blood oxygen levels dropped, his doctors said — on Friday and again on Saturday. The president’s oxygen saturation level was 93 percent at one point, his doctors said, below the 95 percent that is considered the lower limit of the normal range.
Many medical experts consider patients to have severe Covid-19 if their oxygen levels drop below 94 percent. The physicians said Mr. Trump had received supplemental oxygen at the White House on Friday; they were not clear about whether it had been administered again on Saturday, or whether his blood oxygen levels had fallen below 90 at some point.
Dr. Conley said that the president had been given the steroid dexamethasone on Saturday, in addition to remdesivir, an antiviral drug. Dexamethasone has been shown to help patients who are severely ill with Covid-19, but it is typically not used in mild or moderate cases of the disease.
Because of the incomplete picture offered by the president’s doctors, it was not clear whether they had given him dexamethasone too quickly, or whether the president was far sicker than has been publicly acknowledged, experts in infectious disease and emergency medicine said on Sunday.
“The dexamethasone is the most mystifying of the drugs we’re seeing him being given at this point,” said Dr. Thomas McGinn, the physician-in-chief at Northwell Health, the largest health care provider in New York State. The drug is normally not used unless the patient’s condition seems to be deteriorating, he added.
“Suddenly, they’re throwing the kitchen sink at him,” Dr. McGinn said. “It raises the question: Is he sicker than we’re hearing, or are they being overly aggressive because he is the president, in a way that could be potentially harmful?”
The World Health Organization issued guidelines on Sept. 2 recommending that dexamethasone only be given to patients with “severe and critical Covid-19.” The National Institutes of Health has issued similar guidance, specifying that the drug is recommended only for people who require a mechanical ventilator to help them breathe, or who need supplemental oxygen.
A large study of dexamethasone in Britain found that the drug helped those who had been sick for more than a week, reducing deaths by one-third among patients on mechanical ventilators and by one-fifth among patients receiving supplemental oxygen by other means.
Later Sunday, presumably to allay concerns, Mr. Trump posted an upbeat if rambling video praising his doctors at the Walter Reed National Military Medical Center.
“It’s been a very interesting journey,” he said. “I learned a lot about Covid.” He added: “I get it, and I understand it.”
Wearing a dark jacket and no necktie, Mr. Trump stood in the video and spoke energetically and with no apparent trouble breathing..
Determined to reassert himself on the political stage on his third day in the hospital, Mr. Trump then appeared in a black S.U.V., escorted by Secret Service vehicles, on the street outside the hospital. Mr. Trump could be seen in the back, wearing a suit and a mask and waving.
The stunt seemingly placed his Secret Service detail at risk of infection, as many pointed out. “The irresponsibility is astounding,” tweeted Dr. James P. Phillips, the chief of disaster medicine at George Washington University and an attending physician at Walter Reed. He noted that the risk of coronavirus transmission inside a hermetically sealed vehicle was about “as high as it gets outside of medical procedures.”
On Friday, Mr. Trump was given an infusion of an experimental antibody cocktail that is being tested in Covid-19 patients by the drugmaker Regeneron. Mr. Trump is also receiving a five-day course of remdesivir, another experimental drug that is used in hospitalized patients and has been granted emergency authorization by the Food and Drug Administration.
Regeneron’s antibody cocktail is being tested early in the course of the infection, because it fights the virus itself and could prevent it from spreading throughout the body. Remdesivir is also an antiviral drug, but has been commonly used along with dexamethasone, which reduces the body’s immune response and is given later in the illness, when some people’s immune systems go into overdrive and attack their vital organs.
On Sunday, the doctors said that Mr. Trump was in good spirits and that he was walking on his own and not complaining of shortness of breath.
“If he continues to look and feel as well as he does today, our hope is to plan for a discharge as early as tomorrow to the White House, where he can continue his treatment,” one of his doctors, Dr. Brian Garibaldi, said at the briefing on Sunday.
But several medical experts said that the decision to prescribe dexamethasone to Mr. Trump did not align with that optimistic scenario.
Michael Crowley contributed reporting.
As President Trump and some of his associates test positive for the coronavirus, the number of new cases reported each day across the United States has been slowly rising.
The country is at a key moment in the pandemic, and spread of the virus could worsen significantly through the autumn, experts fear, as colder weather forces people indoors. Every day, some 43,000 new cases are being reported — far fewer than during the surge in the summer, but still an uncomfortably large number.
Some of the country’s least populous states are now seeing their highest infection rates.
When coastal cities suffered in the spring, cases remained relatively scarce across most of the nation’s midsection. But since late summer, North Dakota and South Dakota have added more cases per capita than any other state.
Utah recorded 1,387 new cases on Sunday, a single-day record. Four states — Wisconsin, Indiana, Montana and Wyoming — have added more cases in the last week than in any other seven-day stretch of the pandemic.
One significant change from the spring and early summer has been the return of college students to campuses.
The New York Times has identified more than 130,000 cases at more than 1,300 American colleges since the pandemic began.
Some of the worst trouble spots have calmed. Florida is now averaging about 2,300 new cases a day, roughly one-fifth of what it was seeing at its worst. In Arizona, daily case reports have dropped to about 500 on average, down from more than 3,600.
New infections have also plunged in Georgia, Louisiana and South Carolina. Mississippi and Alabama have made significant progress since midsummer as well, though case numbers there remain high.
California and Texas have also seen drops in case numbers. Both states, however, have recorded more than 800,000 cases.
Over a busy weekend of medical briefings, the American public has been looking to Dr. Sean P. Conley — a Navy commander and doctor of osteopathy who has been the White House physician since 2018 — for reassurance about President Trump’s condition.
Instead, experts say, Dr. Conley has delivered confusion and obfuscation. He even confessed that he had misled the public on Saturday about Mr. Trump’s treatment to reflect the “upbeat attitude” of the White House.
On Saturday, he ducked questions about whether Mr. Trump had been on oxygen, then revealed on Sunday that indeed, the president had been on oxygen — an indicator that Mr. Trump’s illness may be classified as “severe.” On Sunday, Dr. Conley was similarly evasive, sidestepping questions about whether the president’s X-rays revealed any lung damage or pneumonia. “I’m not going to get into specifics of his care,” he said.
Caring for any president presents unique challenges. Like all doctors, Dr. Conley is bound by the Hippocratic oath to respect his patient’s wishes for privacy and to keep secret that which “ought not to be spoken of outside.” He is also a Navy officer caring for the commander in chief, whose orders he is obliged to follow.
But all of that must be balanced against the public’s right to have information about the health of the leader of the free world. And this particular leader, Mr. Trump, is well known for not wanting to look weak.
Dr. Conley is supervising a team of medical experts at Walter Reed National Military Medical Center, including Dr. Sean Dooley, a pulmonologist, as well as an outside expert, Dr. Brian Garibaldi, the director of the biocontainment unit at Johns Hopkins Hospital in Baltimore.
To the surprise of many in medicine, one doctor not being consulted is Dr. Anthony S. Fauci, one of the world’s leading experts on infectious diseases. (Dr. Fauci is on the White House coronavirus task force, but he was sidelined when his statements of fact about the virus irritated the president.)
No matter what Dr. Conley says or does not say, his colleagues in medicine agree on one thing: If he is going to put himself in the position of answering questions about the president’s care, he has to answer truthfully and to the fullest extent possible.
“You can’t both wear the white coat and lie, evade, obfuscate the situation,” said Dr. Ezekiel Emanuel, a bioethicist at the University of Pennsylvania, “because you are using the white coat to give yourself credibility.”
Vice President Mike Pence, who would be the most powerful man in the nation should President Trump become too ill to continue his duties, has been on the campaign trail despite having been in close contact with the president and being at high risk of having the virus himself.
“There is no way under the sun that Pence should be anywhere but in his home,” said Dr. Rochelle Walensky, an infectious disease expert at Harvard University. “He was sitting in a sea of people with Covid; there is no way he should go anywhere.”
Mr. Pence and Karen Pence, the second lady, tested negative for the coronavirus for a third day on Sunday, a senior administration official said. They have been tested every day since Mr. Trump and the first lady, Melania Trump, tested positive for the coronavirus, which officials have said was Thursday. But it is possible to test negative and still be infected early in the course of the virus.
Mr. Pence is scheduled to debate Kamala Harris, the Democratic vice-presidential nominee, in Salt Lake City on Wednesday.
Mr. Pence was last in contact with the president on Tuesday morning at the White House. He may have also been in close contact with several others who tested positive after having attended the White House event on Sept. 26 to announce the nomination of Judge Amy Coney Barrett for the Supreme Court.
Mr. Trump began feeling symptoms as early as Wednesday, and several studies have shown that people are most infectious from one to two days before showing symptoms to about two days after. This could mean that Mr. Trump was already highly infectious on Tuesday.
And it puts Mr. Pence and anyone who came into contact with Mr. Trump on Tuesday squarely at risk. Chris Christie, the former governor of New Jersey, who helped the president with debate preparation at the White House from last Saturday through Tuesday, has tested positive.
Former Vice President Joseph R. Biden Jr. is also at risk of being infected, experts say. Although he and Mr. Trump stood more than 12 feet apart at the debate, they were indoors. Studies have shown that indoors, the virus can travel farther than six feet, prompting experts to recommend that Mr. Biden also quarantine and get tested daily. On Sunday evening, the Biden campaign announced he had again tested negative for the coronavirus.
Mr. Biden has continued to campaign, traveling to Grand Rapids, Mich., on Friday, and holding a virtual town hall with a union on Saturday. He is usually seen wearing a mask at campaign events.
Mr. Pence, meanwhile, has traveled to several states and participated in outdoor and indoor campaign events. On Wednesday, he attended a packed fund-raiser in Atlanta, and on Thursday he spoke at two indoor events in Iowa. He did not wear a mask on either day, nor did most attendees.
Mr. Pence’s team has said that he tested negative for the coronavirus on Friday, Saturday and Sunday. But tests for the virus can produce false negatives if used too early in the course of infection. The virus can take up to 14 days to show symptoms, which is why the Centers for Disease Control and Prevention recommends that anyone who has been in close contact with an infected person quarantine for 14 days.
Trump campaign officials said Sunday that Mr. Pence had no plans to curtail his public appearances. “He will be hitting the trail,” Jason Miller, the campaign’s senior adviser, told CNN. “And he’s going to have a very full, aggressive schedule.”
The White House has not sought help from the Centers for Disease Control and Prevention to trace the contacts of people who attended a celebration in the Rose Garden on Sept. 26 for Judge Amy Coney Barrett, according to a federal official familiar with the matter.
Dr. Sean Conley, the White House physician, told reporters on Saturday that his team was working with the agency to trace contacts. But according to the federal official, while the C.D.C. had a team of experts on standby to help the White House, it has not been approached to do so.
In an interview Sunday on the CBS program “Face the Nation,” Dr. Scott Gottlieb, a former commissioner of the Food and Drug Administration, also offered evidence suggesting that no robust contact tracing effort was underway. Dr. Gottlieb said he had spoken to several officials who attended the Rose Garden event and who had not been spoken to by any contact tracers.
“I think they have an obligation to understand how the infection was introduced into that environment,” he said of the White House. “There doesn’t seem to be a very concerted effort underway.”
The celebration of Judge Barrett’s nomination to the Supreme Court on Saturday is looking more and more like a “super spreader event.” At least seven attendees, including President Trump and Melania Trump, have already tested positive.
On Sunday evening, for the first time since the president fell ill, the White House management office sent out a campuswide email about coronavirus protocols at work.
The note, which does not mention that Mr. Trump and the first lady are infected, reinforces protocols that have been in place for several months, urging people to stay home if they experience specific symptoms.
But for the first time, according to one official who has seen the various emails over time, officials said that if people feel they should be working remotely, they should discuss it with a supervisor. That is something that many private employers have offered for months.
Some attendees of the event for Judge Barrett have tested negative, but that does not necessarily mean they are not infected. Negative results are common early in the course of infection, when the levels of virus in the body are still low. For that reason, C.D.C. guidelines recommend that anyone who has been in close contact with an infected person should stay in quarantine for two weeks even if they test negative.
The lack of attention to contact tracing could have devastating consequences for the hundreds of people who have come into proximity with those who may have become infected at the Rose Garden event. Any of them could have caught the virus and gone on to transmit it to many more people.
The C.D.C. has experts who are trained in contact tracing and could have immediately begun identifying and warning people who might have been exposed, working with state health departments. In the case of the White House, “we would help if we were asked,” the official said. But no such request came through, he said.
“We don’t get involved unless we’re asked to get involved,” he said.
In a sharp reversal, Mayor Bill de Blasio of New York announced on Sunday that he would seek state permission to shut down a variety of businesses and schools in nine ZIP codes in Brooklyn and Queens where tests have shown a positivity rate of 3 percent or more for the past seven days.
The move by the mayor — which must be approved by Gov. Andrew M. Cuomo — is the clearest indication of concern by city leaders over the possibility of a second wave in the city, which was ravaged by the virus in the spring.
The mayor’s plan would shut down indoor dining in those nine areas, some of which have large populations of Orthodox Jews. The virus has been spreading rapidly in those communities in recent weeks.
The new shutdown would take effect on Wednesday, if approved by Mr. Cuomo.
In addition, 11 other areas where rates of infection have hovered between 2 and 3 percent will be required to close “high-risk activities,” among them indoor dining, swimming pools and gyms.
It was only last week that the city reopened indoor dining, with restaurants limited to 25 percent capacity; the city’s public schools also welcomed back students, in a bold attempt to restart in-person learning in the nation’s largest school district.
Earlier on Sunday, Mr. Cuomo said that the state would begin “direct enforcement” in 20 ZIP codes this week where the virus is now spiking, using the state police and other state employees to monitor businesses, schools and houses of worship for possible violations.
“We know how to deal with a hot spot,” he said. “But you have to deal with a hot spot.”
The governor made no mention of immediate closings, despite average rates of infection topping 10 percent over the last three days in three separate areas in Orange and Rockland Counties, north of the city. One area, in Orange County, which includes Kiryas Joel, an Orthodox community, averaged more than 20 percent, according to statistics released by the state on Sunday.
In a statement issued after the mayor’s announcement, the governor said that while “the state cannot take over effective enforcement for every jurisdiction,” it would be ready to act if notified by the local authorities. And, he added, “we will close all business activity in the hot spots where the local governments cannot do compliance.”
New York remains the hardest-hit state in the United States, with more than 32,000 deaths, including more than 20,000 deaths in New York City alone.
As President Trump continues to be treated at Walter Reed National Military Medical Center, doctors and senior White House staff members have given conflicting updates about his condition, treatments and when he learned he was infected.
The timeline below is drawn from the president’s tweets, news conferences, statements from the White House and reporting from The New York Times.
On Wednesday, Mr. Trump and his team traveled to Minnesota for a rally that lasted about 45 minutes — about half the length of his typical campaign speeches.
During the event, one of Mr. Trump’s closest advisers, Hope Hicks, started to have symptoms related to the virus.
On the return trip, Mr. Trump slept as some of his advisers spoke about the condition of Ms. Hicks, who was isolated in the back of the plane.
News that Ms. Hicks had tested positive for the virus came on Thursday as Mr. Trump left the White House by helicopter around 1 p.m. for a fund-raiser at his golf club in Bedminster, N.J.
At the event, Mr. Trump appeared before hundreds of supporters, both indoors and outdoors. One person who saw the president there said he was in contact with about 100 people and appeared lethargic.
On a call with Iowa voters and in an interview with Sean Hannity on Fox News, Mr. Trump sounded raspy.
Later that night, Mr. Trump and the first lady, Melania Trump, tested positive for the coronavirus, officials said.
The president had a mild cough, nasal congestion and fatigue.
On Friday, close to 1 a.m., Mr. Trump said on Twitter that he and the first lady had tested positive for the coronavirus.
Later in the morning, Mr. Trump had a high fever and his oxygen saturation levels dipped below 94 percent, said Dr. Sean P. Conley, the White House physician.
The doctor recommended that Mr. Trump be given supplemental oxygen.
“He was fairly adamant that he didn’t need it,” Dr. Conley said. “He was not short of breath. He was tired, had the fever, but that was about it.”
After about a minute on two liters of supplemental oxygen, Mr. Trump’s saturation levels were back over 95 percent, Dr. Conley said. The president stayed on the supplemental oxygen for about an hour at the White House.
That evening, he was taken to Walter Reed National Military Medical Center in Bethesda, Md.
Mr. Trump received an experimental antibody cocktail and was given his first dose of remdesivir, an antiviral drug that has an emergency approval from the Food and Drug Administration as a Covid-19 therapy.
On Saturday, the president’s blood oxygen level dropped for a second time to about 93 percent, which some experts describe as a potential indicator of severe Covid-19, though it was unclear if the president received more supplemental oxygen.
He was given the steroid dexamethasone. A study conducted by scientists at the University of Oxford showed the drug reduced deaths of Covid-19 patients on oxygen by one-fifth.
Mr. Trump was given a second dose of remdesivir and did not exhibit any known side effects, doctors said.
Dr. Conley said that, as of that night, Mr. Trump remained “fever-free and off supplemental oxygen.”
“While not yet out of the woods, the team remains cautiously optimistic,” he added.
Mark Meadows, the White House chief of staff, offered a more somber description of the president’s health, generating skepticism over Dr. Conley’s initial news conference.
The next day, Sunday, the president’s blood oxygen level improved to 98 percent, Dr. Conley said at a news conference.
The president’s medical team hinted at the possibility that Mr. Trump might be discharged to the White House as early as Monday.
Doctors were tracking any damage to his lungs for signs of pneumonia.
Kenzo Takada, the designer whose exuberant prints and volumes helped break the Paris barrier and bring Japanese fashion to the world, died on Sunday at a hospital in Paris. He was 81. The cause was complications from the novel coronavirus.
A spokeswoman for Kenzo, the company he founded, confirmed the news.
“Kenzo Takada was incredibly creative,” said Jonathan Bouchet Manheim, chief executive of K-3, the lifestyle company that Mr. Takada founded in January, though he had retired from fashion in 1999. “With a stroke of genius, he imagined a new artistic and colorful story combining East and West — his native Japan and his life in Paris.”
Known for his beaming smile and mischievous sense of fun, Mr. Takada, who was generally referred to only as Kenzo, shook up the established French fashion world when he arrived — via boat — from Japan in 1964. Though he initially planned to stay only six months, he ended up living in the city for 56 years, and his work opened doors not only for the highly influential Japanese designers who came after him, such as Yohji Yamamoto and Rei Kawakubo, but he also created a new kind of mix-and-match aesthetic that crossed borders and cultures, embraced diversity and influenced a generation.
He died in the middle of Paris Fashion Week, which has been struggling to go on despite the pandemic. A smattering of live shows are taking place at a highly reduced capacity and with mask-wearing guests. The week began as Paris announced that the city is poised to, once again, shut down restaurants and bars if new cases continue to increase.
Saudi Arabia began lifting coronavirus restrictions at Islam’s holiest site in Mecca on Sunday, as a scattering of worshipers performed the umrah pilgrimage for the first time since March.
A maximum of 6,000 pilgrims — a tiny fraction of the usual capacity — will now be allowed to enter the Grand Mosque in Mecca each day, the government said. On Oct. 18, the limit will be raised to 15,000 pilgrims a day.
For now, only Saudi citizens and residents can worship at the mosque, but visitors from abroad may be allowed to do so starting Nov. 1, the government said.
Video images showed socially distanced worshipers circling the black-clad Kaaba shrine at the center of the mosque on Sunday. Muslims wishing to worship must reserve a place in advance and are limited to three hours inside the mosque, which is being sanitized several times a day, the government said.
As the pandemic took hold in the spring and countries closed their borders, the kingdom suspended the practice of the umrah pilgrimage, which can be performed at any time of year, and severely restricted the larger annual hajj pilgrimage, which Muslims are obliged to undertake once in life.
Instead of the usual 2.5 million pilgrims from around the world, the kingdom reportedly allowed just 1,000 people from within its borders to perform the hajj, as it sought to contain an outbreak that spread even within the royal family. As of Sunday, Saudi Arabia has reported a total of 335,997 cases and 4,850 deaths.
In other global developments:
With President Trump hospitalized with Covid-19, Secretary of State Mike Pompeo will cut short a trip to Asia this week, canceling stops in South Korea and Mongolia but continuing with a visit to Japan. Mr. Pompeo earlier alluded to the possibility of curtailing his Asia visit because of the infections in the president’s circle, but a State Department spokeswoman, Morgan Ortagus, did not specify why the schedule had been changed in a statement on Saturday.
Britain reported a record 12,871 new cases on Saturday evening, double the number of daily infections from Friday. The nation is working to contain a second wave, and the government said the spike was the result of a “technical issue” that delayed the publication of some cases. Prime Minister Boris Johnson told the BBC on Sunday that the situation would be “bumpy” until Christmas and potentially longer. He urged Britons to behave “fearlessly, but with common sense.”
Worried that the virus is spiraling out of control, public health officials in Ireland have recommended that the entire country be placed at the highest level of lockdown for up to four weeks. If the government — which appeared taken aback by the recommendations — agrees, severe limits will be placed on all social gatherings.
France reported 16,972 new cases of infection on Saturday, a record, as a surge in cases forced the closure of bars and restaurants in the southern port of Marseille. Rising infection rates mean similar closures could soon apply in the capital, Paris.
Italy is expected to impose new restrictions this week to try to control rising numbers of coronavirus cases, Roberto Speranza, the health minister, said Sunday, the Reuters news agency reported.
Poland’s government said on Sunday that the country had surpassed 100,000 total cases.
Russia on Sunday recorded more than 10,000 new infections for the first time since mid-May, reporting 10,499 cases. President Vladimir V. Putin, who encouraged his country to return to normal, has built himself a virus-free bubble that far outstrips the protective measures taken by many of his foreign counterparts.
India on Sunday reported 75,829 new infections and 940 deaths, a day after it became the third country after the United States and Brazil to pass 100,000 deaths.
Amid the muddled and conflicting information about President Trump’s condition, his allies seized on a video and photos the president posted online in an attempt to rally around a more consistent — and positive — message.
After Mr. Trump posted a four-minute video Saturday evening on Twitter, his family and aides amplified the message that Mr. Trump was in good condition and working hard despite his illness. In the video, he wears a suit and describes feeling well — despite a warning from his own chief of staff that he did not yet face “a clear path to recovery.”
“If only all elected officials had this work ethic,” his son Eric Trump wrote above photographs released by the White House appearing to show the president working from an office suite at the Walter Reed military hospital in Bethesda, Md. He added that his father “is a true warrior. I have admired this unrelenting drive my entire life.”
“One take, from the heart, no teleprompter,” Jason Miller, a senior adviser to Mr. Trump’s campaign, wrote in a tweet reposting Mr. Trump’s direct-to-camera video. “Over to you, Sleepy Joe!” he added, in a jab at Mr. Trump’s Democratic rival, former Vice President Joseph R. Biden Jr. (While there was no evidence of a teleprompter, Mr. Trump does look down at notes in front of him as he speaks.)
And Mr. Trump’s daughter Ivanka, who also posted the video, said she had spoken to her father and that “he is as optimistic, thankful and strong as he looks and sounds in this message to America.”
At the same time, however, Democratic and liberal critics of the president pounced on the video and images of the president as suspicious and potentially misleading. Some online sleuths noted that official photos of Mr. Trump appearing to sign documents in two different rooms, and wearing slightly different outfits, contained metadata with time stamps showing they were taken 10 minutes apart. The metadata later appeared to have been deleted.
Others noted a moment in the video when Mr. Trump’s shoulders suddenly hunch and his face begins to contort midsentence as though he is about to cough before he returns to normal. Video experts said that modern editing tools can smooth out edits that would once have appeared abrupt and noticeable, though The New York Times was not able to verify the claims. The White House did not comment on whether the video had been edited.
Robert O’Brien, the national security adviser, said National Security Council staff members working at the White House complex must now wear face masks when around others or in common areas.
“Over the past couple days as this spread through the West Wing, notwithstanding the bubble that was created here in the testing, we made mask wearing mandatory for National Security Council staff,” Mr. O’Brien told reporters at the White House on Sunday.
He also said he planned to give Mr. Trump a national security briefing on Sunday afternoon, via secure video conference, along with Secretary of State Mike Pompeo and the chairman of the Joint Chiefs of Staff, Gen. Mark A. Milley. Mr. Trump was to receive the briefing in what Mr. O’Brien called a “secure facility” at Walter Reed National Military Medical Center in Bethesda, Md., where the president is hospitalized.
In a separate interview on CBS’s “Face the Nation,” Mr. O’Brien said that Mr. Trump remained “firmly in control” of the country and that the United States remained “safe” despite the president’s illness.
Asked whether he had discussed a potential transfer of power from the president to Vice President Mike Pence, Mr. O’Brien said that scenario was “not something that’s on the table at this point.”
Last week, members of the National Security Council staff, who number just below 120, received an email instructing them to wear masks in common areas and in work spaces if they could not be socially distant from others. The email, reported earlier by CNN and confirmed by a White House official, also urged council aides, most of whom work in the Eisenhower Executive Office Building next door to the White House, to avoid unnecessary visits to the West Wing.
Mr. O’Brien, who contracted a mild case of the virus in July, said the council had imposed safety protocols early in the pandemic.
Two members of the White House residence staff tested positive for the coronavirus roughly three weeks ago, according to two people familiar with the diagnoses.
The people who tested positive were not employees who come in direct contact with the president and the first lady, one of the people familiar with the diagnoses said. But the positive results again raise questions about how and when President Trump may have been exposed to the virus.
Judd Deere, a spokesman for the president, declined to comment specifically on the diagnoses, referring to a statement about not commenting on the personal health of individuals.
The White House “does take any positive case seriously and has extensive plans and procedures in place to prevent further spread,” he said. “A full and complete contact trace consistent with C.D.C. guidelines is included in that and appropriate notifications and recommendations are made. “
Pope Francis criticized the failures of global cooperation in response to the coronavirus pandemic in a document released on Sunday that underscores the priorities of his pontificate.
“As I was writing this letter, the Covid-19 pandemic unexpectedly erupted, exposing our false securities,” Francis said in the encyclical, the most authoritative form of papal teaching. “Aside from the different ways that various countries responded to the crisis, their inability to work together became quite evident. For all our hyperconnectivity, we witnessed a fragmentation that made it more difficult to resolve problems that affect us all,” he added.
“Anyone who thinks that the only lesson to be learned was the need to improve what we were already doing, or to refine existing systems and regulations, is denying reality,” the pope said.
Released amid another Vatican financial scandal and after changes in church rules regarding sex abuse, the letter steered clear of other contentious subjects. It instead returned often to some of the church’s hobbyhorses, including a secularism that has produced what the church sees as a throwaway, consumerist culture.
Francis argued that this was apparent in the treatment of older people during the pandemic.
“If only we might keep in mind all those elderly persons who died for lack of respirators, partly as a result of the dismantling, year after year, of health care systems. If only this immense sorrow may not prove useless, but enable us to take a step forward toward a new style of life,” he wrote.
The pope also warned that the forces of “myopic, extremist, resentful and aggressive nationalism are on the rise.”
On Sunday, more than 40,000 people were expected to run the London Marathon — just not together.
Instead, runners were scattered across Britain and more than 100 other countries, after organizers encouraged the vast majority of participants to run 26.2 miles at a time that worked for them wherever they happened to be.
Those who took part in the geographically distanced race were told to log their performances on a dedicated app to claim their medals and official T-shirts.
The official course in St. James’s Park in central London — 19 laps of 1.3 miles each, plus an additional 1,470 yards — was restricted to a relative handful of elite runners. The race, which was postponed from April, is one of the only major marathons to be maintained in any form this year.
Brigid Kosgei of Kenya, who won the 2019 edition and is the current world-record holder in the women’s marathon, defended her title on Sunday, finishing in 2 hours 18 minutes 58 seconds.
Kosgei, 26, told the BBC that while it was “wonderful to race,” her preparation had been affected by the pandemic.
“I struggled up to the moment I finished,” she said.
In the men’s race, the Ethiopian runner Shura Kitata, 24, won in a sprint finish, crossing the line in 2:05.41, a second before Vincent Kipchumba of Kenya. World-record holder Eliud Kipchoge of Kenya, who has won the London Marathon four times, came in eighth.
Prince Harry said Saturday in a message published by the race’s organizers that “the amazing tenacity of runners from around the world is a reminder of our strength and sense of community during these difficult times.”
President Trump’s bombshell announcement early Friday morning that he and the first lady had tested positive for the coronavirus has set off a frenzy in the White House and beyond as politicians and operatives who have interacted with Mr. Trump in recent days have raced to get their own tests and, in some cases, report the results.
Here is a quick look at the people in Mr. Trump’s orbit and beyond who have spoken publicly about their health and the virus, taken from official statements, and announcements made on social media and by spokespersons.
It can take several days after exposure for the virus to reach levels that are detectable by a test. People show symptoms on average around five days after exposure, but as late as 14 days.
Who has tested positive:
Ronna McDaniel, the chairwoman of the Republican National Committee
Hope Hicks, one of Mr. Trump’s most senior advisers
Bill Stepien, President Trump’s campaign manager
Kellyanne Conway, the former top White House adviser, who attended Judge Amy Coney Barrett’s Supreme Court nomination ceremony at the White House on Sept. 26
Senator Thom Tillis of North Carolina, who participated in a debate against his Democratic challenger on Thursday
Rev. John I. Jenkins, the president of the University of Notre Dame, who also attended the ceremony for Judge Barrett last week
Senator Ron Johnson of Wisconsin, who did not attend Judge Barrett’s ceremony last week
The former New Jersey governor Chris Christie, who helped the president prepare for the debate
Nick Luna, the head of Oval Office operations at the White House
Who has tested negative:
Mike Pompeo, the secretary of state
Steven Mnuchin, the Treasury secretary
William P. Barr, the attorney general
Mark Meadows, the White House chief of staff
Dan Scavino, the White House deputy chief of staff
Jared Kushner, Mr. Trump’s son-in-law and senior adviser
Ivanka Trump, Mr. Trump’s daughter
Donald Trump Jr., Mr. Trump’s son
Barron Trump, Mr. Trump’s son
Eric Trump, Mr. Trump’s son
Lara Trump, Eric Trump’s wife
Tom Perez, the chairman of the Democratic National Committee
Betsy DeVos, the education secretary
Senator Ben Sasse, Republican of Nebraska and a member of the Judiciary Committee. He attended Judge Barrett’s ceremony.
Senator Josh Hawley, Republican of Missouri and a member of the Judiciary Committee. He attended Judge Barrett’s ceremony.
Chris Christie, the former governor of New Jersey who for several days this week helped the president prepare for the debate, said he had tested positive for the coronavirus.
Mr. Christie announced his condition on Saturday, becoming the latest of several Trump associates to get a positive test result.
“I want to thank all of my friends and colleagues who have reached out to ask how I was feeling in the last day or two,” he said on Twitter.
In another tweet later on Saturday, Mr. Christie said he had checked himself in to the Morristown Medical Center in Morristown, N.J., on Saturday afternoon after consulting with his doctors.
“While I am feeling good and only have mild symptoms, due to my history of asthma we decided this is an important precautionary measure,” he said.
Mr. Christie’s statement came one day after Bill Stepien, President Trump’s campaign manager, tested positive for the virus. An administration official confirmed late Saturday that Nick Luna, who serves as Mr. Trump’s “body man” and is constantly in proximity to him, also tested positive.
Mr. Christie and Mr. Stepien were among several advisers who huddled with Mr. Trump and others for debate preparation from Sunday to Tuesday.
That group also included Hope Hicks, one of Mr. Trump’s closest advisers, and Kellyanne Conway, the former senior White House aide, both of whom have since tested positive.
No one wore masks during the preparation, Mr. Christie said.
Ms. Conway and Mr. Christie also attended a White House event on Sept. 26 announcing Mr. Trump’s nominee for the Supreme Court, Judge Amy Coney Barrett.
Others who attended and said they have tested positive include Senator Mike Lee, Republican of Utah; Senator Thom Tillis, Republican of North Carolina; and the Rev. John I. Jenkins, the president of the University of Notre Dame.
As campuses across the United States struggle to carry on amid Covid-19 illnesses and outbreaks, a determined minority are beating the pandemic — at least for the moment — by holding infections to a minimum and allowing students to continue living in dorms and attend in-person classes.
Being located in small towns, having minimal fraternity and sorority life, and aggressively enforcing social-distancing measures all help in suppressing the contagion, experts say. But one major thread connects the most successful campuses: extensive testing.
Small colleges in New England — where the Broad Institute, a large academic laboratory affiliated with M.I.T. and Harvard, is supporting a regional testing and screening program with more than 100 colleges — are showing particularly low rates of infection. The partnership tests students frequently and pays $25 to $30 per test to have the samples processed overnight at the institute’s lab in Cambridge, Mass.
The program has allowed Colby College, with about 2,000 students on its rural Maine campus, to test each student before and after arrival on campus, then twice weekly thereafter, using a nasal swab PCR test that takes less than three minutes to conduct. Faculty and staff members are also tested twice weekly. So far, the campus has had 11 positive tests, a few of which turned out to be false positives, said David Greene, the school’s president.
In one case, the testing identified a student who had apparently caught the coronavirus on the way to campus and did not have a sufficient viral load to test positively upon entry, he said. By the time the infection was caught in the next round of testing two days later, contact tracing revealed that a roommate had been infected.
“It could have been 150 people, and we kept it to one person,” Mr. Greene said.
New York reopened classrooms for hundreds of thousands of students last week, after a tumultuous summer of last-minute changes. But the city’s ambitious plan to randomly test students for the coronavirus in each of its 1,800 public schools will probably be insufficient to catch outbreaks before they spread beyond a handful of students, according to new estimates of the spread of infections in city schools.
The city plans to test a random sample of 10 to 20 percent of people, including students and adults, in each city school once a month starting next week, already a herculean task.
But in order to reliably detect outbreaks and prevent them from spinning out of control, New York may need to test about half of the students at each school twice a month, researchers at New York University estimated. Experiences in Germany, Israel and other countries suggest that outbreaks could spread quickly despite the city’s relatively low rate of infection, the researchers said.
“The outbreaks could be quite large by the time they are detected by the monthly, 10-to-20-percent testing,” said Anna Bershteyn, the lead author of the new analysis and assistant professor of population health at N.Y.U.
The testing issue took on fresh urgency this week, when Mayor Bill de Blasio reported that the city’s average test positivity rate, which has been extremely low throughout the summer, had begun to tick up. If the virus continues to surge, the entire public school system could shutter.
The finding underscores how daunting testing will be in any district trying to reopen for some in-person classes, and particularly in New York, which is home to a system of 1.1 million students, about half of whom returned to classrooms this week.
The N.F.L. postponed a highly anticipated game scheduled for Sunday between the New England Patriots and the Kansas City Chiefs until Monday or Tuesday after positive coronavirus tests on both teams. According to multiple reports, Cam Newton, the Patriots quarterback, was among those who tested positive.
The Patriots confirmed a positive test but did not identify the player. In a statement released Saturday, the team said the player entered isolation and that subsequent testing on players and staff members who had been in contact with him had come back negative.
The new positive tests come after the N.F.L. spent much of the week scrambling to address an outbreak of positive tests among the Tennessee Titans. That team reported 11 positive tests among players and team personnel, which forced the league to push its scheduled Week 4 game against the Pittsburgh Steelers back to Oct. 25, Week 7 of the football calendar.
In a statement, the league said that the Patriots and the Chiefs were consulting with infectious disease experts and working closely with the N.F.L. and the players’ association “to evaluate multiple close contacts, perform additional testing and monitor developments.”
In a normal year, millions of people in South Korea would be spending this weekend visiting family in their hometowns in celebration of Chuseok, the rough Korean equivalent of Thanksgiving.
But this year, the government has asked South Koreans to stay home, to avoid exacerbating the country’s latest coronavirus outbreak.
Many South Koreans have grudgingly followed orders, but their acquiescence comes with an emotional price: A normally joyful time of year now feels empty of its sacred rituals, and clouded with feelings of anxiety and disorientation.
“Watching my parents grow older and change often worries me, but seeing them in person puts my mind at ease again,” said Joo Jae-wook, 57, a retired salesman who has traveled with his brothers to their hometown every Chuseok for the past three decades. “But this year I can’t even do that.”
South Korea, a nation of about 50 million, has reported 421 deaths and more than 24,000 coronavirus infections since the pandemic began, including almost 500 new cases in the past week. The country’s response has been widely praised as a model, but a recent outbreak that began in Seoul has tested the government’s strategy of using social-distancing restrictions and extensive tracking to keep the virus at bay without shutting down the economy.
Last week, President Moon Jae-in told the nation that South Korea’s people were observing Chuseok at a “difficult time,” and that their sacrifices would be rewarded. “The government will surely repay the people who have endured the difficulties by succeeding in controlling the virus and protecting the economy,” he said.