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Dr. Francis Collins, the director of the National Institutes of Health, took issue on Wednesday with President Trump’s suggestion that a coronavirus vaccine would be available by Election Day, as he repeatedly sought to reassure senators and the public that a vaccine would not be made available to the public unless it was safe and effective.
“Certainly, to try to predict whether it happens on a particular week before or after a particular date in early November is well beyond anything that any scientist right now could tell you and be confident they know what they are saying,” Dr. Collins told a Senate panel at a hearing on the effort to find a vaccine.
Wednesday’s hearing, before the Senate Health, Education, Labor and Pensions Committee, came amid growing concern over whether people would be reluctant to take a coronavirus vaccine, and whether Mr. Trump would apply political pressure on his administration to quickly approve one to give him a lift in his re-election bid against former Vice President Joseph R. Biden Jr.
On Tuesday, a group of drug companies all in the race to develop vaccines pledged that they would not release any vaccines that did not follow rigorous efficacy and safety standards. Hours later, a leading vaccine developer, AstraZeneca, announced that it had suspended a large-scale clinical trial of a vaccine candidate after a patient experienced what may be a severe adverse reaction. Dr. Collins pointed to that development as “a concrete example of how even a single case of unexpected illness is sufficient to hold a clinical trial in multiple countries” — and evidence that “we cannot compromise” on safety.
In an interview on “CBS This Morning,” Dr. Anthony S. Fauci, the government’s top infectious disease expert, echoed that sentiment.
“That’s the reason why you have various phases of trials, to determine if in fact these candidates are safe,” Dr. Fauci said, adding that such a halt was “not uncommon at all.”
At the hearing, Democrats on the panel grilled both Dr. Collins and Surgeon General Jerome Adams on the effect of Mr. Trump’s false statements about the vaccine, and whether they would erode trust in the development process. Dr. Collins demurred, however, as Senator Elizabeth Warren, Democrat of Massachusetts, asked him point blank whether Mr. Trump’s misinformation would discourage people from taking the vaccine and hurt the effort to distribute it.
“I’m not sure I know the answer to that question,” Dr. Collins said. When Ms. Warren pressed him again, he added, “I just hope Americans will choose to take the information they need from scientists and not from politicians.”
Three companies are in late-stage, Phase 3 clinical trials that seek to enroll 30,000 Americans, half of whom will be injected with the vaccine candidate and half of whom will get a placebo.
Dr. Collins said he had “cautious optimism” that a safe and effective vaccine would emerge by the end of the year, though he added, “but even that is a guess.”
Even as the trials proceed, there are huge questions about who will get a vaccine first and how it will be distributed. Dr. Adams told the panel that the administration intended to release guidelines later Wednesday that would allow state-licensed pharmacists to vaccinate anyone older than age 3.
AstraZeneca, a front-runner company in the race to develop a coronavirus vaccine, on Tuesday announced a global pause in late-stage trials for its product because of a suspected adverse event.
Several individuals familiar with the event, who spoke on the condition of anonymity, said that an individual in Britain who was enrolled in a Phase 2/3 trial had experienced symptoms consistent with a condition called transverse myelitis, or inflammation of the spinal cord.
The trial’s suspension will allow an independent board of experts to determine whether the participant’s condition was linked to the vaccine or merely coincidental, said Saad Omer, a vaccine expert at Yale University.
Part of this process will include generating a timeline of the participant’s symptoms to see if they match up roughly with when the vaccine was administered. The committee will also investigate other potential causes of the symptoms, in a process of elimination. After determining whether AstraZeneca’s vaccine is a probable culprit, experts will advise the company on whether to resume their trials.
In the interim, no further doses of the vaccine will be administered. It remains unclear how long the evaluation process will take. AstraZeneca representatives did not respond to repeated requests for comment and clarification.
The suspension is the second time that AstraZeneca has halted coronavirus vaccine administration in Britain because of severe neurological symptoms, according to information sheets uploaded to a clinical trial registry that was first reported by Nature News. Another participant developed symptoms of transverse myelitis, researchers reported in July, and was later diagnosed with an “unrelated neurological illness.” After a safety review, trials resumed.
Transverse myelitis is relatively rare, prompting symptoms in roughly 1,400 people each year in the United States, according to the National Institutes of Health. Its root cause is often mysterious, although doctors believe that the syndrome generally results when inflammatory responses in the body go awry, sometimes in response to an ongoing or past infection, said Dr. Felicia Chow, a neurologist at the University of California, San Francisco. “It’s not uncommon that we never figure out the cause,” Dr. Chow said.
There has been some past speculation that vaccines might be able to cause transverse myelitis, she added, but “there’s never been really any clear-cut, definitive proof.”
Should other participants in the AstraZeneca trials develop symptoms consistent with transverse myelitis, “that would raise these questions again,” Dr. Chow said.
The lungs are the coronavirus’s foremost target in the body, and it has been clear for some time that the virus can attack the kidneys, liver and blood vessels as well. About half of Covid-19 patients also report neurological symptoms, including headaches, confusion and delirium — suggesting that the virus might attack the brain.
A new study offers the first clear evidence that in some people, it does just that, in two ways: The virus invades brain cells, hijacking them to make copies of itself, and it appears to suck up all the oxygen near the host cells, starving other cells to death.
It’s unclear exactly how the virus gets into the brain or how often it touches off this trail of destruction. Infection of the brain is likely to be rare, but some people may be susceptible because of their genetic backgrounds, because of a high viral load or for other reasons.
“If the brain does become infected, it could have a lethal consequence,” said Akiko Iwasaki, an immunologist at Yale University who led the work.
The study was posted online on Wednesday and has not yet been vetted by experts for publication. But several researchers said it was careful and elegant, showing in multiple ways that the virus can infect brain cells.
In the new study, Dr. Iwasaki and her colleagues documented brain infection in three contexts: in brain tissue from a person who died of Covid-19, in a mouse model, and in organoids — clusters of brain cells in a lab dish meant to mimic the brain’s three-dimensional structure.
Other pathogens, including the Zika virus, are known to infect brain cells. Immune cells then flood the damaged sites, trying to cleanse the brain by destroying infected cells.
The coronavirus is much stealthier than some other pathogens: It exploits the brain cells’ machinery to multiply, but doesn’t destroy the cells. Instead, it chokes off oxygen to adjacent cells, causing them to wither and die.
The researchers didn’t find any evidence of an immune response to remedy this problem. “It’s kind of a silent infection,” Dr. Iwasaki said. “This virus has a lot of evasion mechanisms.”
As hospitals in Indonesia’s capital near capacity, the authorities will reimpose a partial shutdown on Monday that includes a work-from-home requirement, a ban on large gatherings and restrictions on houses of worship.
“We will pull the emergency brake, which means we are forced to re-implement large-scale social restrictions like in the early days of the pandemic,” Jakarta’s governor, Anies Baswedan, told reporters on Wednesday evening.
Indonesia, the world’s fourth most populous nation, implemented social distancing restrictions early in the pandemic but later relaxed them in the hope of restarting the stalled economy. In recent weeks, however, the number of reported cases has surged past 200,000, and independent experts say the total is likely many times higher.
Indonesia’s health care system is notoriously understaffed and underfunded. More than 185 doctors, dentists and nurses have died from Covid-19, professional associations say.
Since Sunday, Jakarta has been reporting more than 1,000 new cases a day — about a third of the national daily total — and Mr. Anies said the city’s hospitals were filling quickly with coronavirus patients.
He predicted that all hospital beds would be taken by early October and that intensive care units would be full by Sept. 25 if the city did not take immediate action to slow the spread of the virus.
In the neighboring city of Bekasi, another virus hot spot, officials were preparing the city stadium as an isolation center to house people who have tested positive for the coronavirus but do not have symptoms, said the mayor, Rahmat Effendi.
In Jakarta, where the city had reported nearly 50,000 cases and more than 1,300 deaths as of Thursday morning, the designated cemetery for Covid victims has been filling quickly and was expected to run out of room by mid-October.
Mr. Anies said the city was still working out details of restrictions on gatherings, travel, and prayers at mosques, always a sensitive issue in the predominantly Muslim country. Most schools have not reopened since they were shut down months ago — a particular challenge for rural schoolchildren who lack internet and cellphone service.
In other developments around the world:
A day after AstraZeneca announced a global pause in late-stage trials for its coronavirus vaccine, the Serum Institute of India — which has partnered with the company and is shouldering the costs of domestic production — said on Wednesday that the country’s drug regulators had not instructed it to pause domestic trials. “The Indian trials are continuing and we have faced no issues at all,” the institute said on Twitter. India, which has more than 4.4 million confirmed cases, said on Thursday that 95,735 new infections had been reported over the previous 24 hours, a single-day record.
Britain, undergoing a spike in new coronavirus cases, will ban most gatherings of more than six people beginning next week, Prime Minister Boris Johnson said Wednesday. The government’s chief medical officer, Professor Chris Whitty, said that the country’s recent uptick did not merely reflect broader testing.
A fast-moving fire destroyed most of Europe’s largest refugee camp on the Greek island of Lesbos, leaving its 12,000 residents homeless just days after they were collectively quarantined because of a coronavirus outbreak there.
France’s prime minister, Jean Castex, is self-isolating after he came into contact with the director of the Tour de France, who has tested positive. Mr. Castex tested negative on Tuesday, but he will isolate until being retested seven days after the contact took place. France is facing a resurgence, with a daily average of 7,000 cases for the last seven days and an increase in the number of patients in intensive care after months of decline.
China’s biggest air show will go ahead in November, the organizer said on Wednesday, backtracking on an earlier announcement that the event had been canceled because of the pandemic. The biennial International Aviation and Aerospace Exhibition comes amid a steep downturn in the industry.
Germany extended a travel advisory to include all countries outside Europe through Sept. 30. But the foreign ministry said that starting in October, it would evaluate individual non-European destinations case by case, rather than issue another blanket warning.
A photo of an older man having a meal in a pub in Galway, Ireland, started a national conversation about virus regulations and life’s simple pleasures.
Sarah Goldstone got a virus test in Massachusetts after her health insurer said it was “waiving cost sharing for Covid-19 testing-related visits.”
Amanda Bowes, a health policy analyst in Maryland, got hers because she knew a new federal law should make virus testing free for insured patients like her.
Kelly Daisley had one after seeing New York City’s ads offering free tests. “Do it for them,” reads one bus shelter ad near her home, showing a happy family.
All three were surprised when their health insurers said they were responsible for a significant chunk of their bills — in Ms. Daisley’s case, as much as $2,718.
“I had seen so many commercials saying there is testing everywhere, it’s free, you don’t need insurance,” said Ms. Daisley, 47.
For months, Americans have been told not to worry about the costs of virus tests, which are crucial to stopping the pandemic’s spread. Congress passed laws requiring insurers to pay for tests, and the Trump administration created a program to cover the bills of the uninsured. Cities and states set up no-cost testing sites.
Patients, whether with or without insurance, are beginning to find holes in those new coverage programs. Across the United States, people have been hit with unexpected fees and denied claims related to virus tests, according to dozens of bills that The New York Times has reviewed. Insurers have told these patients they could owe from a few dollars to thousands.
The next step is resuming international flights. The first is a Sept. 16 T’way Airlines flight between Wuhan and Seoul, the South Korean capital, China’s state-run media reported on Thursday.
Several carriers are applying for permission to restart direct flights between Wuhan and cities such as Bangkok; Kuala Lumpur, Malaysia; Hanoi, Vietnam; Singapore; and Tokyo, according to a report in People’s Daily, the official newspaper of the Chinese Communist Party.
Thousands of infected travelers who left Wuhan in January, ahead of the Lunar New Year, helped to unwittingly spread the virus across the country and beyond. The industrial hub of 11 million people was placed under lockdown later that month.
Wuhan began to cautiously reopen in April, and other cities have since followed suit, even as experts warn that China may face a Covid-19 resurgence as the weather cools and people spend more time indoors. Earlier this month, Beijing restarted direct flights to Canada, Greece, Thailand and other countries.
Eerily empty this spring, Wuhan’s Tianhe International Airport processed up to 60,000 travelers a day last month, a record since the end of the lockdown, according to state media reports. And by late August, the airport had recovered 90 percent of its pre-pandemic volume of domestic flights compared with the same period last year.
On Thursday, China reported zero domestically transmitted cases for the 25th consecutive day. The Chinese mainland has had a total of almost 93,000 cases and 4,634 deaths, according to a New York Times database.
The former Italian prime minister Silvio Berlusconi was on Sardinia in August, as was his friend, the club owner Flavio Briatore. Now both are among hundreds of cases linked to the island, a favorite of rich partygoers.
It is unclear when or how Mr. Berlusconi and Mr. Briatore got the virus. What is known, though, is that the number of cases on the island shot up from a few dozen before the summer to more than 1,000 in a month.
Mr. Berlusconi, 83, lies in a Milan hospital with pneumonia. Mr. Briatore, who dropped in to pay him a visit at his Sardinian estate and who had publicly complained about what he said was an overreaction by the government to the pandemic, is quarantined.
In March, as cases and deaths exploded in the Italy’s north, the southern island’s governor, Christian Solinas, pleaded with the authorities in Rome to ban travel to Sardinia. The government obliged. For months, the island staved off the worst.
But August has been Sardinia’s hot season since the 1960s, and not even the pandemic could stop it.
Roberto Ragnedda, the mayor of the Sardinian town of Arzachena, said “10 days of madness” in August had caused “enormous damage to our image and to economy.”
What did our Tokyo bureau chief, Motoko Rich, hear when she attended a recent soccer match in Tokyo? Here’s what she wrote about going to the game, which in pre-pandemic times would have been a boisterous experience:
As the players drove the ball down the field, I suddenly heard the distinct crinkle of a plastic bag a full four rows in front of me, where a man was pulling out a chicken drumstick to eat.
This was the sound of Japanese professional soccer in the era of the coronavirus.
While the major sports leagues in the United States and Europe are playing mostly before empty stands or cardboard cutouts, fans in Japan have been attending games since early July, after a four-month hiatus.
But there are trade-offs.
In normal times, Japanese fans are not only loud, they are also extremely orchestrated and utterly disciplined. Nonstop through a match, they sing, cheer, chant, bang drums and wave enormous team flags — a boisterous spectacle that often rivals the actual play on the field for entertainment value.
Now, most of those activities are banned for fear that people might be roused into a frenzy of shouting, with any spray becoming a vector for spreading the virus.
So when I attended a home match on a recent Sunday surrounded by nearly 4,600 fans of FC Tokyo, one of 18 teams in the top tier of the Japan Professional Football League, or J-League, the spectators were scrupulously quiet — except for an occasional crinkle of a food wrapper or a spontaneous burst of applause.
Gov. Andrew M. Cuomo announced on Wednesday that the ban on indoor dining in New York City would be lifted on Sept. 30, a boost to the city’s recovery from the pandemic that would end its status as one of the few places in the nation with a complete ban.
The governor’s announcement, which would allow restaurants to open indoor tables at 25 percent capacity, could be a major milestone in the coronavirus crisis in New York City, where restaurants form a critical part of the city’s economy and its currently moribund tourist trade, and are a vital part of its usually vibrant social fabric.
The announcement came more than two months after the governor and Mayor Bill de Blasio halted a plan to reopen indoor dining at restaurants, citing ongoing concerns about the coronavirus, which has killed more than 30,000 people in New York. But the infection rate in the state has been kept below 1 percent for weeks, allowing for the easing of some restrictions. Indoor dining resumed in neighboring New Jersey at 25 percent capacity last week.
“Because compliance is better, we can now take the next step,” the governor said.
The timing coincided with a date, still three weeks away, that is around when fall weather is likely to put a chill on outdoor tables. Additional restrictions would also be placed on restaurants and their patrons, including temperature checks and a requirement to wear face coverings when not seated. Bars will be used to make drinks to serve tableside and restaurants must close at midnight.
Less than three weeks after Detroit teachers authorized their union to strike over concerns about safety precautions in the city’s public schools, the school year started on Tuesday for the district’s roughly 50,000 students, with buildings only 20 percent full.
Administrators and the union reached an agreement late last month to limit in-person classes to 20 students each and to require that social-distancing measures be in place. But despite the precautions, 80 percent of families opted for remote learning, Chrystal Wilson, a district spokeswoman, said.
Teachers spent time on the first day showing students who attended classes in person how to wear their masks properly and to stay socially distant, Ms. Wilson said.
And there were technical problems in the virtual classrooms. Some teachers had too many students in their online classes — more than 50, in some cases — said Terrence Martin, the president of the Detroit Federation of Teachers. Others logged on to find no students in their classes, he said.
Voncile Campbell, who is teaching math virtually at Bow Elementary-Middle School this year, said she spent much of her time on Tuesday and Wednesday helping her fourth-grade students learn how to use the district’s multiple technology platforms. She said she was supposed to teach her first real lesson on Thursday
“Is that going to happen?” she said. “I’m not sure.”
There were also misunderstandings about digital etiquette rules. One student showed up partially dressed.
“I had to ask him, ‘Could you please go put on a shirt?’” Ms. Campbell said.
Since the start of the pandemic, researchers have been searching for variations in the human genome that may influence the course of Covid-19, the illness caused by the coronavirus.
Early studies pointed to two spots in our DNA. One of them contained a gene that determines our blood type.
But with subsequent studies, the link between Covid-19 and blood type seemed to dissolve into uncertainty. Some experts declared that the jury was still out.
Now, studying the DNA of over one million people, researchers at the consumer genetics company 23andMe have concluded that Type O blood may lower the risk of developing Covid-19.
The scientists posted the results of their study online Monday. Their findings have yet to be peer-reviewed or published in a scientific journal.
Starting in April, 23andMe scientists surveyed customers, asking who among them had tested positive for the coronavirus. Over a million people wrote back, including 15,434 who said they had done so and 1,131 who reported that they had been hospitalized for Covid-19.
The researchers asked a number of other questions on the survey to look for Covid-19 risk factors. In line with previous studies, the researchers found that men were more likely to report having tested positive, as were people of Hispanic and Black descent. African-Americans who tested positive were also more likely to have been hospitalized. Obesity, too, was linked to a high risk of hospitalization.
But the researchers also found that people with Type O blood were less likely to be infected than expected, suggesting that this blood type protects people from the disease. The scientists did not find that any other blood type raised the risk more than others.
Benjamin Neale, a Harvard geneticist who was not involved in the new study, said the link between Covid-19 and the chromosomal region containing the blood-type gene “is definitely bolstered” by the study’s findings. But scientists still do not know exactly what the connection may be.
Mr. Trump acknowledged to the journalist Bob Woodward that he had knowingly played down the coronavirus earlier this year even though he was aware it was “deadly” and vastly more serious than the seasonal flu.
“This is deadly stuff,” Mr. Trump told Mr. Woodward on Feb. 7 in one of a series of interviews he conducted with the president for his coming book, “Rage.” The Washington Post and CNN were given advance copies of the book and published details on Wednesday.
“You just breathe the air and that’s how it’s passed,” the president said. “And so that’s a very tricky one. That’s a very delicate one. It’s also more deadly than even your strenuous flu.”
That was a vastly different story than Mr. Trump was telling the public.
“I wanted to always play it down,” Mr. Trump told Mr. Woodward on March 19. “I still like playing it down, because I don’t want to create a panic.”
In public, Mr. Trump claimed early on that the virus would disappear, predicting in February that by April, “when it gets a little warmer, it miraculously goes away.”
The national security adviser, Robert O’Brien, warned Mr. Trump on Jan. 28 that the coronavirus represented the “biggest national security threat” of his presidency, according to CNN’s account of the book, but Mr. Trump later said he did not remember the warning.
Former Vice President Joseph R. Biden Jr. took aim at Mr. Trump over the revelations during an appearance in Michigan on Wednesday
“He had the information,” Mr. Biden said, accusing Mr. Trump of lying to the public. “He knew how dangerous it was. And while this deadly disease ripped through our nation, he failed to do his job on purpose. It was a life-and-death betrayal of the American people.”
At the White House press briefing on Wednesday, shortly after the book’s contents were reported in the news media, the press secretary, Kayleigh McEnany, claimed that the president had not lied.
“This president does what leaders do, good leaders,” she said, saying “The president has never lied to the American public on Covid.”
Arizona has reported its lowest number of new cases since late March, reflecting the progress made in curbing the spread of the virus after harrowing outbreaks over parts of the summer.
Though Arizona had only 77 new cases on Tuesday, a sharp decline from July, when new cases were reaching 3,800 a day, the seven-day average is more than 500 daily cases, according to a Times database. In total, there have been more than 200,000 cases and more than 5,200 deaths in Arizona, including two new deaths on Tuesday. Tuesday was the first business day since the Labor Day holiday, and case reports across much of the country were lower than usual.
The state led the nation in cases per capita after Gov. Doug Ducey reopened the economy quickly in late spring. Mr. Ducey then reversed himself by allowing cities and counties to issue mask mandates and ordering some businesses to close once again.
The Navajo Nation, which spreads over parts of Arizona, New Mexico and Utah, is also making strides against Covid-19. For the first time in nearly six months, Navajo authorities on Tuesday reported no new cases of the virus.
Still, epidemiologists warn that cases in Arizona could spike again, citing the potential for outbreaks from school reopenings and Labor Day gatherings.
Elsewhere in the United States:
More than 33,000 cases and more than 1,100 deaths were announced across the United States on Wednesday. North Carolina, Idaho and Nebraska set single-day death records.
Treasury Secretary Steven Mnuchin raised doubts on Wednesday about the likelihood of another economic stimulus package being passed this year and said his current focus was on a measure to extend government funding this month. Republicans and Democrats in Congress remain far apart in their views about the scope and cost of another relief bill, and President Trump has been largely disengaged from the negotiations.
Colleges that have reopened for in-person instruction are struggling to contain the spread of the virus among tens of thousands of students. Many have set aside special dormitories to provide isolation beds for infected students and separate quarantine units for the possibly sick. But some undergraduates and epidemiologists say the policies have broken down, often in ways that may put students and college staff members at risk.
In Los Angeles County, Halloween will still be scary this year; it will just have to be scary from inside the safety of one’s own car. According to guidelines published by the Los Angeles County Department of Public Health, door-to-door trick-or-treating is not recommended and haunted house attractions are not allowed during a pandemic. Instead, the guidelines suggest, trick-or-treaters can celebrate in other ways, such as going to watch a scary movie at a drive-in movie theater or eating a Halloween-themed meal at a restaurant outdoors.
A day after Mr. Trump held a large rally in North Carolina without wearing a mask, Dr. Fauci expressed concerns about the example this set. When asked on “CBS This Morning” on Wednesday about whether the sight of such rallies was frustrating, Dr. Fauci said: “Well, yes it is, and I’ve said that often. We want to set an example.”
Senate Democrats released a report on Wednesday that showed that the delivery of prescription drugs by mail slowed over the summer as Louis DeJoy, the postmaster general, enacted cost-cutting changes at the United States Postal Service. That corroborates reports of delayed packages from across the country. Delivery times lengthened by as much as 32 percent, and patients had to wait, on average, an extra day or two to receive their prescriptions, the report said.
A group of gym and boutique fitness studio owners announced a class-action lawsuit on Wednesday against Mayor Bill de Blasio and New York City to allow indoor group fitness classes to reopen in the city.
New York City’s gyms were given the green light to reopen with new safety regulations a week ago; the governor allowed them to reopen statewide as early as Aug. 24 after a similar lawsuit was filed against the state. But indoor boutique studios and group classes, like Pilates, Zumba, yoga and many other flavors of fitness, are still prohibited by the city.
City and state officials have said that group fitness classes are more conducive to spreading the virus than a traditional gym setting, where people often have more space. Mr. Cuomo noted the potential dangers of such classes while announcing the return of indoor dining in the city on Wednesday.
“You’re exhaling deeply, you’re inhaling deeply, you’re perspiring, you’re touching other material,” Mr. Cuomo said. “That is a much riskier situation to be in than sitting at a table with four people.”
Fitness studio owners say that describing their classes as unsafe is inaccurate and unfair, and that if anything they are more carefully controlled than ordinary gyms, where activities are less coordinated.
Charles Cassara, a gym owner and leader of the New York Fitness Coalition, one of the groups behind the suit, called the mayor’s decision to keep studios closed a “sin” and a “disgrace” on Wednesday.
“If he does not open up in a timely fashion, we are all going to close,” Mr. Cassara said.
Britain, undergoing a spike in new coronavirus cases, will ban most gatherings of more than six people beginning next week, Prime Minister Boris Johnson said Wednesday.
“I wish we did not have to take this step,” Mr. Johnson said. “As your prime minister, I must do what is necessary to stop the spread of the virus.”
He stressed hand washing and wearing face coverings, and said the new rule would be in place only “as long as necessary.”
He said the order, which he referred to as the “Rule of Six,” superseded old guidelines and would apply to public and private gatherings.
The government’s chief medical officer, Professor Chris Whitty, said the uptick the country is seeing is not just a matter of testing more people and compared the situation Britain is facing to the one in France, where cases are surging.
Restaurants and other hospitality venues will also now be required by law to take customers’ personal details for contact-tracing purposes. And Mr. Johnson said there would be stronger enforcement of quarantine rules for those entering the country.
The new rules will take effect Monday and people who break them can be fined and possibly arrested.
“You must not meet socially in groups of more than six,” Mr. Johnson said. “If you do you will be breaking the law.”
Like millions of schoolchildren across the country, students in Des Moines’s public schools started classes remotely on Tuesday, despite orders from the governor and a ruling by a state judge requiring the district to hold at least half of its classes in person.
The litigation in Iowa is one of numerous legal battles that have emerged across the country as school districts, elected officials, educators and parents wrangle over balancing educational needs with public health concerns. In North Carolina, a group of parents filed a lawsuit earlier this month against the Charlotte-Mecklenburg school board demanding in-person classes.
In Des Moines, District Judge Jeffrey Farrell on Tuesday denied the school district’s request for an injunction that would allow it to continue holding all of its classes remotely amid rising coronavirus caseloads, which school officials said make their classrooms unsafe.
Despite the ruling, the district again held remote classes on Wednesday, although the school board was meeting with lawyers to discuss options. Another judge made a similar ruling Tuesday against schools in Iowa City, which also started remotely under a two-week waiver from the state that Des Moines did not receive.
Des Moines schools sued the Iowa Department of Education and Gov. Kim Reynolds, a Republican, in August after the governor issued an order requiring schools in the state to offer in-person instruction for at least 50 percent of their classes if the coronavirus positivity rate in their communities is less than 15 percent — triple the rate recommended by the Centers for Disease Control and Prevention. Polk and Warren Counties, home to Des Moines’s public schools, both exceed that federal threshold. Tuesday’s ruling denied the district a temporary injunction while the lawsuit proceeds.
Despite the denial, Des Moines schools will remain closed “until further notice” in order to protect public health, even if that puts the district at risk of losing state funding, the Des Moines superintendent, Thomas Ahart, said in a statement.
Mr. Arhart later said by telephone: “There’s not a way for us to tell our community that we are genuinely protecting their students, or for us to tell our staff that we’re not putting them in harm’s way and to meet the return-to-learn requirements of the state. Those two are incompatible actions.”
Across the United States, colleges that have reopened for in-person instruction are struggling to contain the spread of the virus among tens of thousands of students, with perhaps their most complex problem being what to do with students who test positive or come into contact with someone who has.
Many have set aside special dormitories, or are renting off-campus apartments or hotel rooms to provide isolation beds for infected students and separate quarantine units for the possibly sick.
But some undergraduates and epidemiologists say the policies have broken down, often in ways that may put students and college staff members at risk.
At the University of Alabama in Tuscaloosa and the University of Notre Dame, students have reported their classmates for violating quarantine and wandering outside. At Iowa State University, a student who was waiting for his virus test results said he was sent back to his regular dorm room where he could have infected his roommate.
And at many campuses, students with confirmed or possible infections have flooded social media platforms to describe filthy rooms, meager food rations, lack of furniture, chaotic procedures and minimal monitoring from their universities.
The policy breakdown reflects the chaotic nature of this extraordinary semester, when schools are struggling to deliver both in-person and remote classes; to identify, isolate and treat coronavirus outbreaks; and to maintain safe behavior among sometimes unruly undergraduates.
A day after Mr. Trump held a large rally in North Carolina without wearing a mask, Anthony S. Fauci, the nation’s leading official on infectious diseases, expressed concerns about the example this set.
Appearing on “CBS This Morning” on Wednesday to talk about the hunt for a coronavirus vaccine, Dr. Fauci was asked whether the sight of such rallies was frustrating.
“Well, yes it is, and I’ve said that often,” he said. “We want to set an example.”
Dr. Fauci, whose differences with the president have been noted throughout the pandemic, said that public health measures such as wearing masks, keeping physical distance, avoiding crowds and moving activities outdoors rather than indoors “are the kind of things that turn around surges and also prevent us from getting surges.”
“So I certainly would like to see a universal wearing of masks,” he said.
While Mr. Trump’s recent rallies have been outdoors or in airport hangars, they are certainly crowded, with little evidence of physical distancing. And even in places where there is an official mask requirement, like North Carolina, masks at the rallies are few and far between. The Republican chairman of the county commission where the rally on Wednesday took place said beforehand that the president should wear a mask, given the statewide order on face coverings. Mr. Trump did not.
Senate Democrats on Wednesday released a report showing that the delivery of prescription drugs by mail slowed over the summer as Louis DeJoy, the postmaster general, enacted cost-cutting changes at the United States Postal Service. That corroborates reports of delayed packages from across the country.
Delivery times lengthened by as much as 32 percent, and patients had to wait, on average, an extra day or two to receive their prescriptions, the report said.
Some delays were longer. According to the report, one company said, “The number of orders taking over five days to deliver has risen dramatically since the onset of the pandemic.”
Two Democratic senators, Elizabeth Warren of Massachusetts and Bob Casey of Pennsylvania, collected information from five of the country’s largest pharmacies and administrators of prescription drug programs.
Some deliveries began to slow before Mr. DeJoy, a Republican megadonor and ally of President Trump, took office in June, probably because of the coronavirus pandemic and disruptions in supply chain. But the delays were exacerbated in July after Mr. DeJoy started his cost-cutting measures, the report said.
“He needs to resign,” Senator Warren wrote on Twitter and said that if Mr. DeJoy did not resign, the Postal Service’s board of governors should remove him.
The Postal Service did not immediately respond to the report, but said last week that mail performance had begun to improve.
Reporting was contributed by Aurora Almendral, Troy Closson, Emily Cochrane, Katie Glueck, Michael Gold, Maggie Haberman, Jason Horowitz, Mike Ives, Thomas Kaplan, Patrick Kingsley, Sarah Kliff, Dan Levin, Jesse McKinley, Constant Méheut, Claire Moses, Richard C. Paddock, Alan Rappeport, Motoko Rich, Simon Romero, Christopher F. Schuetze, Dera Menra Sijabat, Natasha Singer, Karan Deep Singh, Daniel E. Slotnik, Mitch Smith, Kaly Soto, Megan Specia, Sheryl Gay Stolberg, Muktita Suhartono, Katie Thomas, Jin Wu, Katherine J. Wu, Elaine Yu and Carl Zimmer.