Los Angeles County, where the virus is surging, urges residents to stay home.

The Los Angeles County Department of Public Health on Friday called on residents to stay home as the virus continues its rapid surge, barring gatherings both in public and at private homes if people are from different households.

The restrictions announced Friday were not unexpected. Los Angeles County officials have been gradually tightening health restrictions, though not yet to the shutdown levels imposed early in the pandemic.

The county had set a threshold for the restrictions of an average of 4,500 daily cases over five days. That threshold was crossed earlier than expected: The five-day average of new cases reported Friday was 4,751. Nearly 400,000 people in the county have had the virus, more than in most states.

The directive allows for church services and protests, noting that both are constitutionally protected rights. It sets maximum occupancy rates for various businesses, including nonessential retail, libraries and recreational activities, and leaves in place a countywide prohibition on in-person dining at restaurants and bars because patrons can’t wear face masks while eating or drinking.

Takeout and delivery services for dining establishments, however, will still be allowed.

The directive is less severe than Gov. Gavin Newsom’s statewide order in March, which closed schools and most businesses and limited public movement with exceptions for essential workers or essential activities like acquiring groceries and medications.

“We know we are asking a lot from so many who have been sacrificing for months on end,” Barbara Ferrer, the public health director, said. “Acting with collective urgency right now is essential if we want to put a stop to this surge.”

The temporary order will take effect Monday and remain in effect through Dec. 20.

For businesses allowed to remain open, patrons must wear face masks and remain at least six feet apart.

Schools and day camps can remain open, according to the directive. However, day camps as well as schools at the high school level and below must close for two weeks if they report an outbreak, which the county defined as three or more cases over 14 days.

Last week, California officials announced a curfew prohibiting nearly all residents of the state from leaving their homes to do nonessential work or to gather from 10 p.m. to 5 a.m.

The new stay-at-home order was described as more limited than the governor’s spring order; in addition to applying only overnight, it has a built-in expiration date for now and applies only to so-called purple-tier counties, which are under the state’s most stringent restrictions in its reopening plan. It is in place until the morning of Dec. 21.

“We are sounding the alarm,” Gov. Gavin Newsom said as the order was issued. “It is crucial that we act to decrease transmission and slow hospitalizations before the death count surges. We’ve done it before and we must do it again.”

On Sunday, the county issued orders for most restaurants to end outdoor as well as indoor dining starting on Wednesday, limiting those businesses to take out, drive-through and delivery services and sparking a backlash among restaurant owners, whose businesses have been slammed.

Los Angeles County is home to some of the most densely populated neighborhoods in the country, many of which have residents living in multigenerational homes and workers who cannot telecommute, according to The Associated Press.

The number of coronavirus infections in the United States shot past 13 million on Friday, worsening the world’s largest outbreak. The milestone came as Americans embarked on a Black Friday that looked different from holidays past.

The U.S. has had one of the world’s highest per capita caseloads in the past week. And every day for more than two weeks, the country has set records for the number of people in the hospital, with the latest figure surging past 90,000 for the first time on Thursday.

At the same time, the nation saw a steep drop-off in new cases on Thursday, but it was a mirage, not progress, because many states did not report data on the Thanksgiving holiday. More than 103,000 cases and more than 1,100 deaths were recorded on Thursday — compared with 187,000 cases and 1,962 deaths that had been recorded the prior Thursday, Nov. 19.

For that very reason, the numbers were artificially high on Friday, when many states reported two days’ worth of data. That pushed the country past 200,000 cases in a single day for the first time, with more than 203,000 reported as of late Friday night, along with more than 1,400 deaths.

And the blurry data could persist longer. Health officials in Vermont have said they would forego reporting on both Thursday and Friday. Additionally, access to testing was likely to decrease for a few days, meaning more infections could go uncounted. In Louisiana, testing sites run by the National Guard were slated to be closed both Thursday and Friday. In Wisconsin, some National Guard testing sites are closed all week.

“I just hope that people don’t misinterpret the numbers and think that there wasn’t a major surge as a result of Thanksgiving, and then end up making Christmas and Hanukkah and other travel plans,” Dr. Leana Wen, a professor at George Washington University and an emergency physician, told The Associated Press.

Public health experts repeatedly warned Americans to stay home on Thanksgiving, and many heeded the advice. But while overall travel within the country was down significantly from prior years, the Transportation Security Administration reported that more than half a million people flew on Thursday alone, in addition to the approximately four million who had already traveled since Sunday. AAA had projected a downturn in road travel, and still expected tens of millions of people to drive to celebrations.

Similarly, the Centers for Disease Control and Prevention list of higher-risk activities for spreading Covid-19 included “going shopping in crowded stores just before, on, or after Thanksgiving,” an attempt to persuade people to sit tight — or make purchases online — on Black Friday.

The latest virus surge began accelerating across much of the country in mid-October. The nation went from eight million cases to nine million in just over two weeks in October; from nine to 10 million in 10 days; from 10 million to 11 million in just under seven days; and from 11 million to 12 million in just five days, hitting that milestone on Nov. 20. The pace to the 13 millionth case slowed, coming after seven days.

From New Mexico to Minnesota to Florida, hospitals are teeming with record numbers of Covid-19 patients, and the overflow is not limited to people with the virus.

One non-Covid patient in Madison, Wis., lay in excruciating pain on a gurney for 13 hours in an emergency room hallway. She could hardly get the attention of the overwhelmed doctors and nurses. A Missouri resident with a brain abscess had to wait a day before flying to another state for surgery.

Nurses say they are forced to care for too many patients at a time because there is not enough staff. Some hospitals have had to turn away transfer requests for patients needing urgent care or incoming emergencies.

Smaller hospitals have had to beg larger medical centers repeatedly to take just one more patient, but many of the bigger hospitals, their own halls and wards overflowing, have sharply limited the transfers they will accept.

Despite months of planning, many of the nation’s hospital systems have no available beds and are seeing widening shortages of nurses and doctors. And rising coronavirus infection rates among nurses and other frontline workers have doubled the patient load on those left standing.

Health care systems “are verging on the edge of breaking,” Dr. Michael Osterholm, a member of President-elect Joseph R. Biden’s Covid-19 advisory council, warned in a podcast.

The public does not realize how dire the situation is, Dr. Osterholm said, and may respond only “when people are dying, sitting in chairs in waiting rooms in emergency rooms for 10 hours to get a bed, and they can’t find one, and then they die.”

More than 101,000 people living and working at nursing homes and other long-term care facilities in the United States have died after contracting the coronavirus, a New York Times analysis of federal, state and local data has found, as the country’s daily death toll from the virus has risen above 2,000 Americans in recent days.

Nursing home populations are particularly vulnerable to the virus, which is especially lethal to older adults who have underlying health conditions, and which can spread easily in congregate facilities.

The Times analysis has uncovered more than 724,000 coronavirus cases infecting people at some 27,000 long-term care facilities. Deaths related to Covid-19 in these centers account for about 40 percent of the country’s pandemic fatalities.

The American Health Care Association and National Center for Assisted Living, a trade group, has warned that cases have been surging in long-term care facilities in recent weeks.

Many nursing homes, which have also struggled with the damaging effects of isolation on their residents, have tried to plan special events for Thanksgiving for those who may not be able to see their families.

Julie Beckert, a spokeswoman for ProMedica Senior Care, which operates more than 400 care facilities, said that staff have organized a “turkey trot” through the halls and have asked families and communities to arrange holiday parades outside of their facilities, so residents can watch from the windows.

Britain asked its drug regulator on Friday to consider AstraZeneca’s coronavirus vaccine for emergency approval, forging ahead in the face of considerable uncertainty about the vaccine’s effectiveness as the government tries to corral a pandemic that has killed more than 66,000 people in the country.

The request was one of a series of steps that Britain has taken to put itself near the front of the pack of countries hurrying to assess coronavirus vaccine candidates. The country’s drug regulator said on Monday that it intended to decide on an emergency approval for a vaccine made by the American pharmaceutical giant Pfizer and a German company, BioNTech, “in the shortest time possible.”

The degree to which AstraZeneca’s vaccine, which was developed by the University of Oxford, is effective across all age groups remains unclear.

After AstraZeneca announced this week that the vaccine appeared to be up to 90 percent effective, the company has acknowledged a key dosing error. The study participants in whom the vaccine was 90 percent effective had mistakenly been given a half dose of the vaccine, followed a month later by a full dose. Among those who received two full doses, the effectiveness dropped to 62 percent. And the people who received the smaller dosing regimen were 55 years old or younger, making it difficult to know if the more promising results would hold among older people, who are especially vulnerable to Covid-19.

That has eroded the confidence of some scientists and created uncertainty about whether additional testing would bear out the apparently spectacular results.

“I can understand why they’ve taken it forward; it still works,” Stuart Neil, a professor of virology at King’s College London, said of the British regulators. “But we’ve still got no idea whether it works well enough.”

When the coronavirus forced an abrupt switch to remote learning in the spring, many U.S. school districts made major changes in student report cards — dropping letter grades, guaranteeing A’s or ensuring that performance during the pandemic would not count against students.

That changed this fall. Although some schools continue to be lenient, many others have returned to their normal grading policies. And in at least some large districts, more students are failing than in past years, with the most vulnerable seeing the biggest declines.

In Houston, the nation’s seventh-largest public school district, which started the fall remotely, 42 percent of students failed two or more classes in the first grading period, compared to 11 percent in a normal year, The Houston Chronicle reported.

In Chicago, the nation’s second-largest district, 13 percent of high school students failed math in the fall quarter, compared to 9.5 percent last fall, The Chicago Tribune reported. Students will return to classrooms there in January, according to the city’s current plan.

And in Northside Independent School District in San Antonio, one of the nation’s 30 largest, the share of students failing at least one course in the first grading period increased from 8 percent last year to roughly 25 percent. More than half of students have opted to remain remote, and those students are disproportionately poor, said the superintendent, Brian T. Woods.

“We’re obviously dealing with unprecedented learning loss and course failure,” he said, “and it’s going to take years to mitigate.”

At the Fairfax County Public Schools, the largest district in Virginia and 11th-largest in the country, an internal analysis found that the percentage of middle school and high school students earning F’s in at least two classes had jumped from 6 percent in the first quarter a year ago to 11 percent this year. Fairfax County has brought back only a small fraction of its 188,000 students for in-person instruction.

Already disadvantaged students appear to be faring worse in remote classes, putting them at increased risk of long-term disengagement and dropping out.

Fairfax County found that students who had performed well before the pandemic were still doing well — better than predicted, in fact — while those who had struggled before were doing even worse now. Among students learning English and students with disabilities, the rate of failure had more than doubled.

The district said it had made adjustments to try to help struggling students complete assignments, including allowing schools to offer “catch up” days and setting limits on much homework. But one critic thought the district and teachers needed to change their approach.

“Where’s the grace?” tweeted Melinda D. Anderson, an education journalist, suggesting that teachers needed to adjust their expectations and work differently with students during the pandemic, and that the district should restructure its grading to reflect the “current learning reality.”

With the emergence of what seem so far to be safe and effective coronavirus vaccine candidates, it appears that humanity may be the winner once again in the unending evolutionary competition between viruses and people.

But vaccines do not stop the process of evolution. David A. Kennedy and Andrew F. Read of The Pennsylvania State University, specialists in viral resistance to vaccines, wrote in PLoS Biology recently that there is always the chance that any virus can evolve resistance to a vaccine. As vaccines are tested and come into use during the pandemic, they urge monitoring of how the coronavirus responds, just in case.

“Nothing that we’re saying is suggesting that we slow down development of vaccines,” Dr. Kennedy said. And resistance evolves over time, after vaccines come into use, so the authors are not raising any concerns about the safety or efficacy of any current vaccine candidates.

A concern about resistance caused Denmark to call for a cull of all its farmed mink because a mutation in infected mink that had been passed on to people seemed worrisome, although these worries have eased.

One mutation found so far seems to help the virus spread, but does not make it resistant to vaccines or make people sicker.

Researchers at the University of Pittsburgh discovered another mutation in the virus of a kind that hadn’t been seen in coronaviruses before that suggests that the coronavirus may have the potential to develop vaccine resistance. They are currently studying that mutation to learn more. That study was posted online but has not yet appeared in a peer-reviewed journal.

For much of the year, every time Hong Kong beat back a surge of coronavirus cases, new problems would pop up weeks later.

Similar patterns hold true in other parts of Asia that are still fighting day-by-day battles to keep their Covid-19 rates from spiraling out of control. And the latest waves of infection are proving harder to trace than earlier ones were — just as winter forces more people indoors and raises the risks of transmission.

Japan and South Korea are experiencing some of their highest single-day tallies since the pandemic began, driven largely by diffuse clusters in the Tokyo and Seoul metropolitan areas. Tokyo alone reported a record 570 new infections on Friday, and greater Seoul reported more than 300 on Saturday.

Hong Kong is reporting about 65 new cases a day, fewer than the 100-plus cases that it reported on some days over the summer. But the Chinese territory is facing a surge that is driven in large part by what experts call untraceable “silent” transmissions.

“We’re getting better at having a large testing capacity, and we have a lot of resources for contact tracing, but the cycle repeats,” said Kwok Kin-on, an epidemiologist at the Chinese University of Hong Kong.

Compared with the United States and Europe, much of East Asia still has the virus relatively in check. Hong Kong, with a population of around 7.5 million, had a total of 6,039 cases and 108 deaths as of Saturday, a low rate for any city.

But the region’s recent setbacks underscore the challenges that the world will continue to face until there is a widely available vaccine. As cases have soared back to alarming levels in recent weeks, South Korea, Japan and Hong Kong have had to quickly recalibrate their strategies.

Travel bubbles that were announced with great fanfare are now on hold. Weeks after reopening, schools have been shut again. Bars and restaurants are closing early or shifting to takeaway menus.

“We need solidarity in this kind of situation, but as everyone knows, it’s not easy,” said Dr. Kim Woo-joo, an infectious disease specialist at Korea University in Seoul.

Prime Minister Narendra Modi of India announced on Friday that he would personally tour three laboratories developing coronavirus vaccines, as his government seeks to balance the colossal logistical and technical challenge of vaccinating a billion people against pressure to revive sagging economic growth.

India enters this test with marked advantages. It already runs the world’s largest immunization program, reaching more than 55 million women and children a year, with protections against polio, measles and other diseases.

The country is also home to some of the world’s largest vaccine developers, with five different Indian-developed vaccines currently undergoing clinical trials. Adar Poonawalla, chief executive of the Serum Institute of India, said this week his company would prioritize vaccine supply to Indians over other countries.

But a vaccine program of this scale — the first phase is intended reach 250 million Indians — involves extraordinary challenges: Most Indians get their health care privately. There is not enough cold storage to reach a vast rural population. And in a country that struggles with corruption, there are worries about fake vaccines and line-jumpers.

Mr. Modi last week warned regional leaders that the country is nowhere near a finish line.

“We have to absolutely reawaken the people to the dangers of the virus,” he said last week. “Let’s not forget India has emerged from a deep ocean of crisis and we don’t want to drown in shallow waters.”

But Mr. Modi, whose political rise was propelled by the promise of accelerating growth, faces his own pressures. He has said he wants India to be a $5 trillion economy by 2024, when he is expected to run for a third term.

Instead, the country has entered its severest recession since at least 1996, when the country first began publishing its gross domestic product numbers.

The Indian economy shrank 7.5 percent in the three months that ended in September, faster than any other major nation’s, with unemployment already at a four-decade high.

Officials have lifted some of the lockdown restrictions in the hopes of stimulating growth — and further spreading the coronavirus. Infections have declined from a September high, but experts worry that the lull is temporary.

Over the past month, the number of coronavirus cases has increased tenfold in the New York city of Buffalo and its surrounding suburbs. Hospitalizations already have surpassed the levels seen in the spring. And the Covid-19 hotline for Erie County, where Buffalo is situated, is getting “annihilated,” the health commissioner said, with 1,500 calls in one 24-hour period this week.

“The second wave is here, and it is here with a vengeance,” Mark Poloncarz, the county executive, said at a news conference, urging residents to take the surge seriously.

Western New York, a bustling five-county region of some 1.4 million people along the Canadian border and the Great Lakes, has emerged as the biggest trouble spot of the state’s second coronavirus wave. If New York City was the hot spot of the spring, then this area seems to presently have that distinction.

Normally known for its neighborliness, its Buffalo Bills football team and its namesake spicy chicken wings, the region now gets regular criticism from Gov. Andrew M. Cuomo for its average positive test rate, which has remained around 5 percent for two weeks.

The rise in Erie County has been a more extreme version of what is happening statewide, and more so resembles the uptick in other regions of the country. Since mid-October, the number of cases in the county has gone from 322 per week to 3,449 per week. Hospitalizations have risen from 84 on Nov. 10 to 264 on Nov. 23. While hospitals have sufficient beds for now, county officials said, staff is being stretched thin.

Forty people have already died of the virus in November, bringing the total coronavirus fatalities in the county to 779 people, according to a New York Times database.

But, in an encouraging sign, Erie County’s infection rate has leveled off at around 7 percent in the last few days, indicating that some restrictions are having an effect. As the message has gotten through, there are now lines to get coronavirus testing, and masking in public places is generally good, residents said, although there has been some pushback regarding current virus restrictions.

“I do believe the vast majority of people in my community are taking it seriously, whether they live in the city of Buffalo or they’re in a rural community,” Mr. Poloncarz, a Democrat, said in an interview. “But there are some folks who are not. And unfortunately, those individuals put at risk the entire community for further shutdowns.”

sports roundup

For the second time this week, the N.F.L. has rescheduled the matchup between the Pittsburgh Steelers and the Baltimore Ravens, this time to Tuesday night, from Sunday, after the coronavirus outbreak in the Ravens’ clubhouse spread further on Thursday, the original day of the game.

It will be the second N.F.L. game of this season on a Tuesday night, after the Titans beat the Bills on Oct. 13. Because the Ravens are now playing on Tuesday, their following game, scheduled for Thursday, two days later, against the Dallas Cowboys, will now be played on Monday, Dec. 7, assuming the outbreak in Baltimore does not spread further.

If more games have to be postponed this season, the league may add an 18th week to the 17-week regular season to allow for makeup games. The start of the playoffs would then be pushed back a week.

In other sports news:

• Ohio State University said Friday night that it had canceled Saturday’s football game at the University of Illinois after people inside the fourth-ranked football program, including Coach Ryan Day, tested positive for the virus. The university said all team-related football activities had been paused indefinitely. Day is the second high-profile college coach to test positive in the last several days; on Wednesday, the University of Alabama’s Nick Saban said he had tested positive and would miss this weekend’s game against Auburn University.

• Officials said Friday that the Pinstripe Bowl, which was to be played at Yankee Stadium in New York City, had been canceled. Organizers of the game, which was to include teams from the Atlantic Coast and Big Ten Conferences, cited the recent increase in virus cases and travel restrictions for their decision. At least eight bowl games will not be played as planned this season.

As Americans spent a holiday torn between hope and heartbreak — with the promise of coronavirus vaccines competing with the reality of empty seats around the Thanksgiving table — European nations planned to emerge from lockdowns while still struggling to contain the virus in the weeks before Christmas.

It has been a month since most countries in Europe tightened restrictions to try to get a resurgent virus under control, and while the economic and emotional costs are high, the logic of lockdowns is simple: The tighter the restrictions, the more success in stopping new infections. Caseloads have fallen in Britain, France, Spain and other European countries.

“We must learn from the summer and not repeat the same mistakes,” Ursula von der Leyen, the president of the European Union’s executive arm, told lawmakers in Brussels this week. “Relaxing too fast and too much is a risk for a third wave after Christmas.”

No country has figured out the perfect balance, and even nations that won praise for their handling of the virus have struggled to contain a second wave.

Germany passed one million total infections on Friday, and the country’s daily death toll climbed above 400 for the first time this week. So Germany is tightening the reins.

Spain, which had eased restrictions in June, added new ones in September and later in several regions, including the capital region of Madrid, ahead of a long holiday weekend in early December. No one will be allowed to travel outside their region of residency except for essential reasons between Dec. 4 and Dec. 14.

Ireland, Italy, France and Belgium, however, announced that they were moving to ease restrictions.

Leo Varadkar, Ireland’s business minister, said on Friday that stores, restaurants, gyms and bars will reopen in the next week or so, bringing as many as 150,000 people back to work, Reuters reported. The Italian government said it would ease restrictions in five regions — including Lombardy, which encompasses Milan — starting on Sunday. Belgium will reopen nonessential stores, museum and swimming pools on Dec. 1, the government announced on Friday. Bars, restaurants and cafes will remain closed.

And France will begin loosening its restrictions on Saturday in a three-step plan, coming off of stringent restrictions imposed at the end of October that led to a fall in cases. Small businesses will be allowed to reopen and places of worship permitted to hold services for up to 30 people.

“The peak of the second wave of the epidemic has passed,” President Emmanuel Macron of France said this week.

In two weeks, if new cases remain low, museums, French cinemas and theaters will be allowed to reopen, and people will be permitted to travel to spend Christmas with family.

“But I call upon your sense of responsibility: This will certainly not be a Christmas like the others,” Mr. Macron said.

Under the French plan, restaurants, bars and gyms will be the last to reopen, on Jan. 20.

Prime Minister Boris Johnson of Britain has opted for a “tiered system” in England, with different regions facing different restrictions when the country emerges from its tough national lockdown next week.

But even before the country’s lawmakers vote on the measures, the government faced criticism that the “tiers” were really just another word for localized lockdowns.

More than 23 million people in England will be placed under the tightest restrictions. Another 32 million will fall under the second of the three tiers, and just 1 percent of the population will fall under the least restrictive tier.

In what promises to be the largest mass testing for the coronavirus in Europe to date, Austria will begin systematically testing its population next week.

Following the lead of Slovakia and the Italian province of South Tyrol, Austria hopes that after bringing new infections under control through restrictions on movement and business, the testing will now allow it to better stop outbreaks before they become unmanageable.

“It provides an opportunity to localize a high number of infected people,” Chancellor Sebastian Kurz told journalists last week, on the day that he announced the government had bought enough rapid antigen tests for the entire population. “So that one can break infection chains.”

Britain has also used mass testing, in Liverpool, where a total of around 200,000 people have been tested and around 1000 cases detected. According to the U.K.’s health secretary, Matt Hancock, the project helped reduce the spread of the disease and when England’s national lockdown ends on Dec. 2, Liverpool will avoid the toughest set of coronavirus restrictions the government intends to apply in the country.

As the second wave of the virus swept across the country this fall, health authorities had lost the ability to trace a majority of the new infections.

Despite one of the strictest lockdowns in Europe — during which Austrians are not allowed to leave their dwellings except for essential reasons, schools remain closed and only supermarkets, pharmacies, banks and post offices are open — the country still has one of the highest infection rates in Europe.

As the extreme restrictions start to show results and the government considers easing some of the measures, officials hope wide-scale testing will help provide a way forward in the central European nation of nearly nine million people.

Starting next week, Vienna, and two western states, Vorarlberg and Tyrol, will start testing. Supported by the national army, firefighters and local authorities, testing centers will be set up in congress centers, community halls and other large spaces. The three big centers in Vienna are expected to test 150,000 people daily.

By Christmas the entire country is expected to have completed the first round of testing.

Those who test positive will have to go into isolation and might be retested, a government spokesman said on Friday.

Unlike the mass test in Slovakia, where those who did not get tested were threatened with home isolation, the tests in Austria are voluntary. Last week Mr. Kurz said he believed as many as half of the country’s population of 8.6 million would get tested. The government has secured more than 7 million tests.

“I see it as an essential step to bridge the time until a vaccine is available,” said Mr. Kurz.

GENEVA — In late May, the American ambassador in Geneva, Andrew Bremberg, went on a rescue mission to the World Health Organization headquarters. He told its director general, Tedros Adhanom Ghebreyesus, that despite weeks of threats that President Trump would quit the health organization over his frustrations about the organization’s dealings with China on the pandemic, the relationship could still be salvaged.

Mr. Bremberg hand-delivered a list of seven demands that American officials saw as the beginning of discreet discussions.

Hours later, Mr. Trump took the lectern outside the White House and blew it all up, announcing that the United States would leave the W.H.O. The announcement blindsided his own diplomats and Dr. Tedros alike.

The W.H.O. leader refused to make concessions or counteroffers, according to American and Western officials. And Mr. Trump ultimately made good on his promise to abandon a health agency that the United States helped form a half-century ago.

The final list emerged from discussions between the White House, State Department and the Department of Health and Human Services. In Geneva, Mr. Bremberg consulted with European allies, who were eager to keep Mr. Trump from abandoning the health organization, Western diplomats said.

By late May, the list stood at seven items. Six were focused on the pandemic, with touches of Trump administration politics sprinkled throughout:

• The W.H.O. should investigate the handling of the outbreak and the source of the virus.

• Dr. Tedros should call on China to provide live virus samples and stop censoring Chinese doctors or journalists. This would have been a significant break for the W.H.O., which rarely criticizes members.

• Dr. Tedros should say that countries were right to consider travel restrictions during the pandemic — a break from the longstanding advice that limiting travel would not slow the virus but would harm economies and delay medical treatment. This risked dragging the W.H.O. into the presidential campaign, as Mr. Trump had made travel restrictions a rallying cry. Ceding to the demand could also have been seen as allowing the United States to strong-arm health policy.

• The W.H.O. should dispatch a team to Taiwan to study its successful pandemic response. Beijing, which claims the self-ruled island as its own, exerts tremendous pressure to keep the W.H.O. from engaging with Taiwan’s government.

• The W.H.O. should pre-qualify coronavirus drugs and vaccines for use around the world, once they were authorized by major regulators in the United States, Canada, Europe or Japan.

The final demand was that Dr. Tedros should ensure that countries like the United States that contribute heavily to the W.H.O. are proportionally represented on the organization’s staff.

Black Friday deals in the travel industry are bigger, better and longer this year, as operators seek to kick-start travel planning in the wake of promising coronavirus vaccine news. Most sale terms acknowledge the inevitable disruptions wrought by the pandemic with flexible cancellation policies and some even throw in travel insurance that will cover your treatment if you are diagnosed with Covid-19 while traveling.

Experts advise holding off on any deals in the next few months, because discounts may get even better as hotel stays, cruises and airline bookings remain depressed. But deals on the far horizon, when vaccines may be widely available, are a more enticing gamble.

“If you can get those reservations with full flexibility, that might be a free option you want because I would expect a big uptick in demand,” said Christopher Anderson, a professor of operations management in Cornell University’s hotel school.

Early on, sales seem to be trending to far horizons. Hurtigruten, the Norway-based expedition cruise line, said half of its Black Friday sales, running until Wednesday, were for itineraries in 2022. G Adventures, a small group tour company with Black Friday deals through Nov. 30, said most of its sale bookings are for June through October of next year.

Many sales are yet to start, including up to 70 percent off more than 1,000 tours worldwide at TourRadar, an online agency.

“We’re a little nervous about how it will do, but hopefully the vaccine news drums up some interest for tours later in 2021,” said Cameron Papp, a spokesman for TourRadar.

College football players across the United States are accustomed to playing and practicing through Thanksgiving weekend, but the surging coronavirus is forcing some teams to make changes large and small to their well-honed routines.

At Colorado, for example, the group holiday meal for football players, a ritual since at least the mid-1990s, will not happen. The team has dispensed with all communal meals this year.

“Everything has been grab-and-go, even on the one road trip,” said David Plati, an associate athletic director at Colorado.

The New York Times contacted all 65 football programs in the Power 5 conferences to ask how they were handling Thanksgiving this season. Of the 47 that responded, most said they would treat this week like any other in the virus-infected season.

Players on the University of Illinois football team, which will host the fourth-ranked Ohio State Buckeyes on Saturday, will be tested for the virus between 6 a.m. and 7 a.m. on Thursday, practice at 8 a.m. and have a team Thanksgiving meal at 11 a.m., according to Kent Brown, an associate athletic director.

“The schedule isn’t much different than past seasons, although players were able to leave campus to gather for Thanksgiving at a local team member or coach’s house for Thanksgiving before reporting back Friday morning,” Brown said. “But in the past, players never had to test for Covid every morning.”

At Ohio State, adapting to the coronavirus pandemic means postponing a beloved rite. The Buckeyes typically have their final regular-season practice on the morning of the holiday. The practice usually concludes with Senior Tackle, when each senior addresses the team and then hits a blocking sled or tackling dummy one final time.

Afterward, players who live near the Columbus campus often take some teammates home for Thanksgiving, while others will have their own families in town or go to a coach’s house.

“This year, however, no one will be going home for Thanksgiving and the team will dine together on Thursday,” Jerry Emig, an associate athletic director, wrote in an email. “Senior Tackle won’t take place until later. We fly to Illinois Friday afternoon.”

New York City streets will officially be devoid of throngs of the jolliest — and perhaps most inebriated — St. Nicks this year. SantaCon, the daylong bar-crawling event that some people love, and many love to hate, has been canceled.

“All of the reindeer got the ’rona so, the elves have advised Santa to hold off the in-person merriment,” SantaCon’s organizers wrote on their website. “Remain home and stay on the good list.”

SantaCon came to New York City in 1997, having already hit Portland and Seattle. Revelers usually dress up as Santa, elves or reindeer, sometimes making their own holiday-related costumes, and cram 12 days of Christmas boozing into one. The event brings troves of visitors from the tristate area, and plenty of eye rolls from nonparticipating New Yorkers.

This year’s festivities were called off the same day that Gov. Andrew M. Cuomo of New York announced a plan to combat the coronavirus during the winter season and warned that the holidays will be telling of the state’s recovery.

On the SantaCon website, the countdown was adjusted forward to the 2021 date. As of Friday, there were 349 days to go.

Kindergarten enrollment in American schools has plummeted during the pandemic, potentially setting back educational and social development for children at a critical age and impacting public school budgets for years to come.

Most states don’t require kindergarten attendance. As a result, the drop in enrollment at that age has been steeper than at other levels — down 14 percent in Arizona, for example, compared to 5 percent across all grades. Nicole Swartz, an Arizona parent who did not enroll her son this fall, told AZfamily.com, “I just really disagreed with just the mental well-being of what would happen with a 6-year-old sitting at a laptop all day.”

Parents made similar decisions across the country. Pre-K and kindergarten enrollment fell 18 percent in Massachusetts, compared to declines of almost 4 percent for other grades. In Ohio, kindergarten enrollment declined in nearly every local school district.

The youngest students, many experts agree, are worst suited for remote learning. They’re squirmy. They can’t figure out how to work computers without help. And much of their learning is social, emotional and motor skill-based.

But younger students might also be best positioned to return to schools safely, at least for now. Growing evidence suggests that they are less likely to transmit the coronavirus to adults or to suffer severe symptoms.

Some parents have turned to parochial and private schools, which could have a significant impact on public schools in states that use enrollment to allocate funding. That has already happened in South Dakota’s largest district, Sioux Falls, where 300 fewer students may mean a loss of $2.5 million in state financial aid.

In Georgia, where kindergarten enrollment dropped 11 percent this fall, public schools could lose $100 million in funding.

“If you lose five students in a classroom, you can’t turn down the heat by five students,” Stephen Owens, a senior policy analyst at the Georgia Budget and Policy Institute, told WABE. “You can’t fire one-twentieth of a teacher.”

After 28 days without any new cases or deaths from the coronavirus, the state of Victoria in Australia, which endured one of the strictest lockdowns in the world in recent months, announced on Friday that it had eliminated the virus.

“Today, we mark the 28th day of zero cases across our state,” Daniel Andrews, the premier of Victoria, told reporters on Friday. “That is something that all Victorians should be fundamentally proud of.” On Dec. 6, Mr. Andrews is scheduled to announce a further easing of restrictions before Christmas.

In July, after a breach in Melbourne’s hotel quarantine system caused an outbreak of the virus, the Victoria state authorities clamped down by enforcing a strict lockdown that included travel regulations and mask rules. Restrictions have largely eased, but people in Victoria are still required to wear masks while indoors, and there are limitations on both indoor and outdoor gatherings.

Public health experts said the state’s success was proof that when the public adhered to strict regulations, the virus could successfully be eliminated.

Many Victorians celebrated the news online. “In the depth of that grim, grim winter I didn’t dare hope this was possible,” Miki Perkins, a local reporter, wrote on Twitter.

Richard Denniss, a prominent Australian economist, also said on Twitter that the state’s stamping out of the virus proved that trusting in public health experts worked, and was also good for Australia’s economy. “Wow! Just wow!” he wrote. “Science works.”