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The Indianapolis Colts on Friday briefly joined the growing group of N.F.L. teams dealing with a potential outbreak of coronavirus cases. Except hours later, the team announced that it had been wrong: The “four individuals” who had tested positive for the virus were re-tested and found to be negative.
Hours after the Colts said they were closing their practice facility, the New England Patriots — who had just emerged from a virus-inflicted week off — also called off their Friday session after recording at least one new positive. The Patriots said the team also was waiting for the results of a follow-up test for a second player to confirm whether he, too, was positive.
The confusion in Indianapolis, though, mirrored a similar series of events last Friday involving the Jets, who closed and then quickly reopened their training facility after an initial positive result was not confirmed in a second test. But the uncertainty and disruption also cast new doubt on the reliance on rapid testing to spot, and prevent, virus outbreaks as the league plows ahead with its schedule.
The rash of false positives echoed several other incidents that have made headlines in recent months. In August, Gov. Mike DeWine of Ohio tested positive on a rapid test, only to confirm thrice by a laboratory test that he did not have the coronavirus. And on Oct. 2, officials in Nevada issued a statewide directive to nursing homes to halt use of two government-issued rapid tests that had produced a concerning number of false positives that could not be confirmed by more accurate tests. Under pressure from the federal government, the state reversed the order a week later.
Although faster, more convenient, and cheaper than typical laboratory tests, rapid tests for the coronavirus are far less accurate. They more often miss cases of the coronavirus, as well as mistakenly label healthy people as infected.
Still, rapid tests make up a growing contingent of the testing landscape in the United States. In September, the White House announced detailed plans to ship 150 million rapid tests manufactured by Abbott Laboratories to governors and vulnerable communities around the nation.
Much of the scrutiny on rapid tests has focused on false negatives, which can hasten the spread of disease when cases are missed. But false positives can be damaging as well, keeping employees out of workplaces and triggering unnecessary anxiety.
In some cases, people who receive false positives may even be isolated with individuals who are actually harboring the virus, raising the risk of further spread.
The news of the new Patriots’ new case came a day after two of the team’s most important players, quarterback Cam Newton and cornerback Stephon Gilmore, returned to practice after a stay on the team’s reserve/Covid-19 list.
Newton, who joined the Patriots this season, and Gilmore, the reigning N.F.L. defensive player of the year, are expected to return when the Patriots face the Denver Broncos on Sunday afternoon. The team said the game, which had been postponed a week after New England’s earlier virus outbreak, would go ahead as planned.
In Indianapolis, the Colts called off practice ahead of their own Sunday game after their latest round of testing produced multiple positives. But within hours, the team said the initial results had been wrong.
“The four positive samples were re-tested and have been confirmed negative,” the team said in an update posted on Twitter. After consulting the league, the Colts said, they had reopened their practice facility “and will continue preparation for Sunday’s game.”
The Colts were just the latest team to announce positive tests in the past few weeks, a group that already included the Tennessee Titans, the Patriots and, on Thursday, the Atlanta Falcons. The outbreaks have scrambled the N.F.L. schedule, forced the league to strengthen its virus protocols, and raised questions about the league’s decision to press ahead with its schedule without creating a restricted environment like the so-called bubble used by the N.B.A.
Several games have been postponed or rescheduled already, each one causing a cascading series of changes in the complicated matrix that is the league’s schedule. Any complications with Sunday’s Patriots-Broncos game would create the most serious scheduling issues yet. When the league postponed the teams’ meeting last weekend, it solved the scheduling problem by allowing both New England and Denver to use the open date as their bye week, and shuffling several games against other opponents later in the season.
But since N.F.L. teams only get one bye week per season, that has left the league with no flexibility if it is forced to postpone any more games involving either team. By insisting on its traditional schedule format, even as the virus cases continue to rise in dozens of states, the N.F.L. has little choice but to try to play Sunday’s game — provided the Patriots do not confirm any additional cases — or pursue adding an 18th week to the calendar to allow for makeup games.
In late September, a Nobel Prize-winning economist emailed Dr. Scott W. Atlas, a White House coronavirus adviser, in what he saw as a last-ditch effort to persuade the Trump administration to embrace a dramatic increase in testing and isolating infected patients. The plan was designed to appeal to President Trump, who has complained that positive tests make his administration look bad and would not “generate any new confirmed cases.”
Dr. Atlas, a radiologist, told the economist, Paul Romer of New York University, that there was no need to do the sort of testing he was proposing.
“That’s not appropriate health care policy,” Dr. Atlas wrote.
Dr. Atlas went on to reference a theory that the virus can be arrested once a small percentage of the United States population contracts it. He said there was a “likelihood that only 25 or 20 percent of people need the infection,” an apparent reference to a threshold for so-called “herd immunity” that has been widely disputed by epidemiologists.
The call for more widespread testing and isolation, Dr. Atlas wrote, “is grossly misguided.”
The exchange highlights the resistance within the White House toward adopting a significantly expanded federal testing program, including efforts to isolate infected patients and track the people they have been in contact with, even as infections and deaths continue to rise nationwide. That resistance has become a sticking point in negotiations over a new economic stimulus package, with the administration and top Democrats disagreeing over the scope and setup of an expanded testing plan.
Many public health experts, and some economists like Mr. Romer, say that a far more sweeping testing program would save lives and boost the economy by helping as many Americans as possible learn quickly if they are sick — and then take steps to avoid spreading the virus.
Dr. Atlas and other administration officials playing influential roles in the government’s virus response effectively say the opposite: that more widespread testing would infringe on Americans’ privacy and hurt the economy, by keeping potentially infected workers who show no symptoms of the virus from reporting to their jobs.
The Mountain West, which for months avoided the worst of the pandemic, has rapidly devolved into one of the most alarming hot spots in the United States, which recorded its eight millionth confirmed case on Thursday.
Seventeen states, including many in the Mountain West, have added more cases in the past week than any other week of the pandemic. And the spread through sparsely populated areas of rural America has created problems in small towns that lack critical resources — including doctors — even in ordinary times.
Wyoming, which did not have 1,000 total cases until June, recently added more than 1,000 in a single week. Reports of new infections have recently reached record levels in Alaska, Colorado and Idaho. And Montana, where more than half of the state’s cases have been announced since August, is averaging more than 500 cases per day.
One place where the infections have spread has been local jails, which are confined, often crowded spaces. They are risky venues for inmates and workers, but the short-term holding facilities also pose a threat for surrounding communities because people filter in and out of them constantly.
For months, the jail in central Montana’s Cascade County was free of the coronavirus, which seemed as distant a threat as it did in much of the rural Mountain West.
Then a few people who had the virus were arrested. By the time Paul Krogue, the jail’s medical director, realized there was a problem, nearly 50 inmates were infected. After weeks battling to contain the outbreak, Mr. Krogue got a call that infections were spreading to a side of the jail that had been virus-free.
“I just kind of lost it, like, ‘My God, I don’t know how much longer I can do this,’” Mr. Krogue, a nurse practitioner, recalled. “I was just scared that I’m not going to be able to see it through, that I’m going to get sick — you just feel so exhausted and it’s just a lot.”
Now more than 300 inmates and staff members have been infected in a facility meant to hold 365 people, Cascade County’s first major outbreak in a region where the virus is suddenly surging.
— Lucy Tompkins, Maura Turcotte and
The Trump administration said Friday that it would contract with CVS and Walgreens pharmacies to provide free coronavirus vaccines, once they are available, to residents of long-term care centers around the country, offering one of the first clues into how vaccines will be distributed.
The partnership will “provide convenient and free vaccination to residents of nursing homes across America, another historic achievement in our efforts to get a safe and effective vaccine to Americans as fast as possible,” Alex Azar, the secretary of the Department of Health and Human Services, said in a prepared statement.
No coronavirus vaccines are currently ready for approval by the Food and Drug Administration, and the timeline for their deployment is unclear. However, the statement said that the program, called the Pharmacy Partnership for Long-term Care, is being established with its goal of having at least one vaccine available by the end of the year.
The vaccines under the program would to be available for residents in skilled nursing facilities, nursing homes, assisted living facilities, residential care homes, and adult family homes as well as staff members who have not been previously vaccinated.
The plan is part of Operation Warp Speed, the Trump administration’s multibillion-dollar high-speed effort to develop and distribute coronavirus vaccines.
Four companies are testing coronavirus vaccines in late-stage clinical trials in the United States. Pfizer has been the most aggressive in its timeline estimates, but its chief executive said today that it would not apply for emergency authorization before the third week of November. The other three companies — Moderna, AstraZeneca and Johnson & Johnson — have said that later in the year is more likely, matching the predictions of federal health officials.
AstraZeneca and Johnson & Johnson’s trials have been paused for potential safety concerns, which could further delay their outcomes.
Latino and Black Americans died in disproportionately high numbers relative to the general population from May to August this year, according to a report issued by the Centers for Disease Control and Prevention on Friday. Latino deaths rose by more than 10 percent over that period, the largest increase of any group.
The trendline is not new. Early numbers had shown that Black and Latino people were being harmed by the virus at higher rates.
The report notes that of the 114,411 coronavirus-related deaths reported to the C.D.C.’s National Vital Statistics System during that time frame, slightly more than half were white; about a quarter were Latino and nearly 19 percent were Black, figures that are far higher than their portion of the general population (about 18 percent for Latinos and 13 percent for Blacks).
Regardless of race and ethnicity, those aged 65 and older represented the vast majority — 78 percent — of all coronavirus deaths over those four months.
The geographic impact of coronavirus deaths shifted from May to August as well, moving from the Northeast to the South and West. And though the virus moved into parts of the country with higher numbers of Hispanic residents, the report’s data showed that alone does not entirely account for the increase in percentage of deaths among Hispanics nationwide.
“Covid-19 remains a major public health threat regardless of age or race and ethnicity,” the report states. It attributes an increased risk among racial and ethnic groups who might be more likely to live in places where the coronavirus is more easily spread, such as multigenerational and multifamily households, as well as hold jobs requiring in-person work, have more limited access to health care and who experience discrimination.
In July, federal data made available after The New York Times sued the Centers for Disease Control and Prevention revealed a clearer and more complete picture of the racial inequalities of the virus: Black and Latino people have been disproportionately affected by the coronavirus in a widespread manner that spans the country, throughout hundreds of counties in urban, suburban and rural areas, and across all age groups.
Belgium will impose a nationwide curfew and shut all cafes, bars, and restaurants for a month starting Monday.
The curfew will be in place from midnight to 5 a.m., and alcohol sales will be forbidden after 8 p.m. Companies must allow employees to work from home, and gatherings in private homes should be restricted to four visitors, officials said. The measures will be re-evaluated in two weeks.
Belgium has recorded more than 48,000 cases over the past seven days, roughly a quarter of the total 191,959 cases it has seen since the start of the pandemic. Of more than 10,000 deaths, 200 have occurred in the last week.
“To some people those measures may appear unjust, but this virus is unjust,” Prime Minister Alexander de Croo said at a news conference. “It attacks disproportionately those most vulnerable.”
He added that although Belgians were attached to their freedoms, they were also attached to their health.
The country has had an uneven path through the pandemic. It had one of the world’s highest per capita death rates through much of the spring, as the virus tore through nursing homes while hospitals refused to accept infected residents. And in late September, the country eased restrictions even though infections were on the upswing.
In other developments around Europe:
Prime Minister Sanna Marin of Finland said she had left a European Union summit in Belgium “as a precautionary measure” and was returning home to undergo a coronavirus test, The Associated Press reported. She had attended a meeting in Finland on Wednesday with a lawmaker who later tested positive for the virus. Ms. Marin’s announcement came a day after the European Commission’s president, Ursula von der Leyen, left the summit because one of her close staff members tested positive. Also Friday, a special European Union meeting on China scheduled for next month in Berlin was canceled as cases in the German capital continued to rise.
Greece imposed a lockdown on the northern region of Kozani on Friday, closing shops and restaurants and banning travel outside the region after a spike in new cases. The restrictions will apply until Oct. 29. Kozani is the first Greek region to reimpose such measures, and will also ban gatherings and require face masks in public. Schools remain open. Although Greece has done relatively well in curbing the spread of the virus compared to its European neighbors, recording just under 24,000 cases and 482 deaths, recent weeks have seen cases rise.
A Berlin court ruled against a city order that forced bars and restaurants to close at 11 p.m., but upheld a ban on alcohol sales starting at the same time. The decision, in which the justices said that it was not apparent that the rule on closings would help to contain the virus, came less than a week after the restrictions went into effect. The justices relied on data from health authorities who found that most new infections come from private parties or institutions like senior homes, hospitals, places of worship, or travel. City officials had not yet decided whether to appeal.
Under rules starting Friday in Scotland, couples who marry or enter into civil partnerships will no longer be required to wear face masks during the ceremony. In workplaces, masks will now be mandatory in cafeterias, except for when seated at a table, and, starting Monday, face coverings will be required in communal areas in offices. The country already requires face masks to be worn on public transport, in shops and other indoor public spaces.
As the coronavirus caseload in the United States soars past eight million, epidemiologists warn that nearly half of the states are seeing surges unlike anything they experienced earlier in the pandemic.
Reports of new cases this month have trended upward in all but 11 states, and more than 65,000 cases were announced across the country on Thursday, the most in a single day since July.
Uncontrolled outbreaks in the Midwest and Mountain West are driving the surge, according to a New York Times database. Some of the states with the most extreme growth had relatively few cases until recently, and rural hospitals have been strained.
Per capita, North Dakota and South Dakota are adding more new cases than any states have since the start of the pandemic. Wisconsin — which reported more than 4,160 new cases on Friday, a single-day record for the state — has seven of the 10 metropolitan areas in the United States with the highest rates of recent cases.
The U.S. Surgeon General, Jerome M. Adams, traveled to Neenah, Wisc., to announce the opening of a testing site there in an attempt to curb the spread of the virus in the state. He said on Friday that Wisconsin is “one of our red states, meaning your positivity rates are over 10 percent.”
The state’s positivity rate is 21 percent, according to a New York Times database, meaning that about one in five tests come back positive.
In Minnesota, officials reported 2,290 new cases on Friday, surpassing the state’s previous single-day record, which was 1,516 new cases reported on Oct. 10.
“What’s happening in the Upper Midwest is just a harbinger of things to come in the rest of the country,” said Michael Osterholm, an infectious-diseases expert at the University of Minnesota.
Further west, Colorado, Montana and New Mexico — fueled in part by a surge in the county that includes Albuquerque — were among the 19 states that were reporting seven-day records as of Thursday night. New infections are also emerging at record levels in Idaho and Wyoming. Officials in Wyoming, the least populous state in the country, reported 290 new cases on Friday, a single-day record.
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Signs of the uptick are already appearing east of the Mississippi River.
In the Northeast, where cases have been relatively low since a spring surge, the number of new ones is moving upward again. And in the South, where cases spiked this summer, there are worrisome trends in West Virginia and Kentucky.
The number of cases alone is not a full measure of the nation’s outbreak, in part because they come at a time when testing is more widespread than it was a few months ago. Deaths from Covid-19 have also been relatively flat in recent weeks, with an average of about 700 per day.
Still, said Caitlin Rivers, an epidemiologist at Johns Hopkins University, “we are headed in the wrong direction.”
“That’s reflected not only in the number of new cases but also in test positivity and the number of hospitalizations,” she added. “Together, I think these three indicators give a very clear picture that we are seeing increased transmission in communities across the country.”
High levels of infection in colleges and universities, Dr. Osterholm said, are serving as one source of the spread. Transmission also has been prevalent at events such as funerals, family barbecues and birthday parties, he said, adding that the comeback of sporting events and dining has also added to the spread this fall.
“Pandemic fatigue has clearly set in for large segments of the population,” he said.
Dr. Anthony S. Fauci, the nation’s top infectious disease expert, said on Thursday that the current situation was worrying as winter approaches.
But President Trump continued to downplay the resurgence of this virus, saying he did not support the strictest restrictions by local officials to limit its spread.
“We’re not doing any more lockdowns,” he said. “We’re doing fine.”
A federal judge ruled on Friday that Gov. Andrew M. Cuomo’s new restrictions on services at Roman Catholic churches in parts of New York City that have been hit hard by the coronavirus did not violate the Constitution’s protection of religious freedoms.
The ruling, by Judge Nicholas G. Garaufis of Federal District Court in Brooklyn, was the latest legal victory for Mr. Cuomo in his broader efforts to stem a second wave of the virus in New York.
Last week, two other Brooklyn federal judges rejected emergency requests by the Diocese of Brooklyn and Orthodox Jewish groups to set aside the state’s new restrictions on religious gatherings in parts of Queens and Brooklyn.
Under the governor’s rules, houses of worship in zones with the highest infection rates are limited to 25 percent capacity or a maximum of 10 people, while those in less severe hot spots are allowed to operate at 50 percent capacity.
Lawyers for the diocese had argued in court papers that the regulations violated the First Amendment by imposing capacity limits on at least 26 parishes in Queens and Brooklyn.
In his decision, Judge Garaufis acknowledged that the diocese had “done everything it could be expected to do and more” to conduct services safely and that the restrictions clearly harmed religious groups.
Nonetheless, he wrote, he believed that “based on the evidence submitted, that the state’s policy is guided by science, not a desire to target religious practice” and that the potential risk of blocking the restrictions now was too great to do so.
“If the court issues an injunction and the state is correct about the acuteness of the threat currently posed by hot-spot neighborhoods,” he wrote, “the result could be avoidable death on a massive scale like New Yorkers experienced in the spring.”
More than 1,000 current and former epidemic intelligence officers — the “disease detectives” of the Centers for Disease Control and Prevention — have signed an open letter decrying the politicization of the agency and calling for it to be restored to its “indispensable role” in fighting the coronavirus pandemic.
The letter has been gathering signatures since May, when it was first posted on Medium, but only recently surpassed the 1,000 mark, organizers said. It was republished on Friday with 1,044 signatories by the The Epidemiology Monitor, a trade publication that devoted its entire October edition to calling for a restoration of the C.D.C.’s reputation.
The letter speaks to the growing sense of despair inside the disease control centers, where career government scientists are appalled by White House interference in their decision-making and are calling for their director, Dr. Robert R. Redfield, to push back. Many fear the Trump administration is doing irrevocable harm to the agency’s reputation.
“The absence of national leadership on Covid-19 is unprecedented and dangerous,” the letter states, adding that states and territories “have been left to invent their own differing systems for defining, diagnosing and reporting cases of this highly contagious disease.”
When the letter was first written, the authors state, the Covid-19 death toll had surpassed 100,000 in the United States — it is now twice that. “We urgently call upon the American people to demand and our nation’s leaders to allow C.D.C. to resume its indispensable role.”
The signatories represent more than one quarter of all the epidemic intelligence officers who have been trained since the service began in 1951, said Dr. Charles Rabkin, who helped organize the petition. There are names of so-called “E.I.S. officers” from every class with the exception of 1953; the first one listed, Dr. Henry R. Shinefield, is 97, Dr. Rabkin said.
Six months after a virus outbreak on the aircraft carrier Theodore Roosevelt triggered a political tsunami in Washington that led to the firing of the ship’s captain and the subsequent resignation of his boss — the acting secretary of the Navy — the novel coronavirus has returned to the ship.
The Navy said that two sailors aboard the nuclear-powered Roosevelt, which is at sea near San Diego, tested positive for the virus in the past three days. Both of the sailors have been evacuated, and the people aboard the ship with whom they had contact have been quarantined.
“The sailors self-reported after experiencing symptoms, received immediate medical treatment, and were transported off the ship for isolation,” said Commander Zach Harrell, a spokesman for the Naval Air Forces. He said that contact tracing aboard the ship had been completed.
The reappearance of the virus aboard the Roosevelt immediately sparked worries among crew members who remember the torturous experience of the spring, when an onboard outbreak spread to some 1,100 sailors, and led to a weekslong stay in Guam and the firing of the ship’s commander, Capt. Brett Crozier, after he wrote a widely distributed letter appealing for help.
After he was fired by a political appointee of President Trump, the saga took on new meaning. A video of hundreds of cheering sailors yelling “Captain Crozier!” as he departed the aircraft carrier, went viral. Efforts by the acting Navy secretary at the time, Thomas B. Modly, to right the crisis ended up leading to his resignation.
In other news from around the United States:
Two members of the U.S. energy secretary’s security detail have tested positive for the coronavirus, the Department of Energy announced late Thursday. The secretary, Dan Brouillette, has tested negative, but “out of an abundance of caution,” he and his team have cut short a multi-state trip and are driving back to Washington and following C.D.C. guidance, according to a statement by an agency spokeswoman.
Eighteen members of the Yale University men’s hockey team have tested positive for the coronavirus, according to an email sent by a school official Thursday, prompting Yale to pause all in-person varsity and intramural athletics indefinitely.
A Centers for Disease Control and Prevention report published Friday, about an indoor hockey game in Florida in June that has been linked to 15 infections, amplified concerns about the safety of indoor sports. The player believed to have spread the virus developed symptoms the day after the game. Indoor ice rinks, the report said, are an ideal transmission environment because of the deep breathing that happens during intense exertion and the proximity between players during the game and in the locker rooms.
Gov. Philip D. Murphy of New Jersey announced an administrative shakeup at the state’s Department of Military and Veterans Affairs, which runs nursing homes where 190 residents’ deaths have been linked to the coronavirus. A new commissioner of the department was named on Friday and directors at two state-run nursing homes, where outbreaks are being investigated by the state attorney general, are being replaced.
Irving Pressley McPhail, the president of Saint Augustine’s University, a historically Black university in Raleigh, N.C., died of complications from Covid-19 on Thursday evening, the chairman of the school’s board of trustees, James Perry, said. Mr. McPhail, who became president of the school in July, did not contract the virus at the university, Mr. Perry said.
As the coronavirus pushes the curve of U.S. infections upward for a third time, public officials and families are rethinking how to celebrate Halloween, balancing the risk of increased transmission with the interests of a public reluctant to give up holiday traditions.
In several states, including California and Massachusetts, governors have discouraged trick-or-treating but not issued an outright ban. Public health experts, along with the Centers for Disease Control and Prevention, have warned that the practice could lead to a spike in cases.
“I’m advising people to stay home,” said Dr. Dean A. Blumberg, the chief of the Pediatric Infectious Diseases Division at the University of California Davis Children’s Hospital. “It doesn’t seem worth it to me. It doesn’t seem worth the risk, not only for the family to risk transmission but for the community to result in outbreaks like we saw after Memorial Day.”
The C.D.C., in its Halloween safety guidelines, classified traditional trick-or-treating as a high-risk activity, along with indoor haunted houses and crowded costume parties.
The agency, along with some public officials, is imploring families to find new, safer ways to celebrate. They suggest costume contests via Zoom, candy scavenger hunts in the home or yard and scary movie nights.
If a family does decide to trick-or-treat, experts have urged families and children to wear protective masks in addition to costume masks.
Teresa Tomb, one of the organizers of an annual Halloween parade in Lexington, Ky. — the theme of which combines zombies with Michael Jackson’s “Thriller” — said the city canceled the parade this year, but replaced it with a socially distant, multi-day gathering at a park, where people can dress up and dance in their zombie costumes.
“You kind of reach a certain acceptance that this is what we have to do,” she said. “It will just be a special year.”
A small charity in Jerusalem is offering an under-the-radar service treating mostly ultra-Orthodox and older Covid-19 patients in their homes, even in severe cases where health experts say it could endanger lives.
Drawing on the services of a few doctors — and dozens of volunteers, most without medical training — it operates out of a basement in Mea Shearim, a Jerusalem stronghold of the most extreme anti-Zionist Jewish sects that shun cooperation with the state.
The charity has attracted patients who sense that remaining with family — and avoiding public hospitals — outweighs the risks. But the project is also tinged with a general distrust of government among the ultra-Orthodox community, which appears to be increasingly going it alone in handling the pandemic and many other aspects of daily life.
Since the home-care initiative was reported by Israel’s N12 news service this week, health officials and experts have responded with a mix of condemnation and curiosity.
Dr. Sharon Elrai-Price, a senior Health Ministry official, denounced the operation as a “dangerous” departure and said the ministry was looking into the legality of some aspects of it. But Dr. Gabriel Barbash, a leading Israeli professor of epidemiology, is among those who view the charity’s approach as a possible way to ease the load on hospitals and worthy of further study.
The debate comes as Israel is under its second national lockdown after daily infection and death rates soared to among the highest in the world, and ultra-Orthodox areas top the virus hot spots. Health officials say that about 50 percent of those aged over 65 and under 18 who are infected in Israel are from the ultra-Orthodox community, though it makes up no more than 13 percent of the country’s nine million citizens.
The actual infection numbers may be even higher: The charity does not report coronavirus cases to the authorities, which may be skewing the national virus data on which policymakers base their decisions.
In a flurry of memos released this week and last, the White House physician, Dr. Sean Conley, declared that President Trump no longer posed a transmission risk to others — an assessment, he noted, that was largely based on the results of “advanced diagnostics.”
Outside experts have also said that Mr. Trump, who reportedly began feeling sick about two weeks ago, is probably no longer contagious.
But in fact there exists no test that can definitively determine whether someone who was infected with the coronavirus can still spread it.
“We do not have a test for cure, and we do not have a test for infectiousness,” said Omai Garner, a clinical microbiologist at the University of California, Los Angeles.
Not all coronavirus tests are designed to detect the same parts of the virus. And a negative on one test does not necessarily guarantee a negative on another.
As recently as Tuesday, for instance, a rapid antigen test called the BinaxNOW was unable to detect the coronavirus in Mr. Trump. But results yielded from a laboratory test, which used a slower but more accurate technique called polymerase chain reaction, or P.C.R., showed he still carried genetic material from the virus at low levels in his body.
“We don’t just look at these tests in the context of ‘Coronavirus, yes or no,’” said Karissa Culbreath, a clinical microbiologist at TriCore Reference Laboratories in New Mexico.
There is no definitive threshold at which researchers can say someone is or is not infectious, she said, and it’s very possible to be antigen negative but P.C.R. positive.
Pfizer’s chief executive said on Friday that the company would not apply for emergency authorization of its coronavirus vaccine before the third week of November, ruling out President Trump’s assertion that a vaccine would be ready before Election Day on Nov. 3.
In a statement posted to the company website, the chief executive, Dr. Albert Bourla, said that although Pfizer could have preliminary numbers by the end of October about whether the vaccine works, it would still need to collect safety and manufacturing data that would stretch the timeline to at least the third week of November.
Close watchers of the vaccine race had already known that Pfizer wouldn’t be able to meet the Food and Drug Administration’s requirements by the end of this month. But Friday’s announcement represents a shift in tone for the company and its leader, who has repeatedly emphasized the month of October in interviews and public appearances.
In doing so, the company had aligned its messaging with that of the president, who has made no secret of his desire for an approved vaccine before the election. Mr. Trump even singled out the company by name and said he had spoken with Dr. Bourla, whom he called a “great guy.”
Dr. Eric Topol, a clinical trial expert at Scripps Research in San Diego, said that while Pfizer officials had assured him that a vaccine would likely not be authorized before the election, the company’s letter on Friday was “even more solid about their not being part of any political machinations.”
“This is good, really good,” said Dr. Topol, who was one of 60 public health officials and others in the medical community to sign a letter to Pfizer urging it not to rush its vaccine.
Dr. Bourla has pushed back against any suggestion that the company’s vaccine timeline was politically motivated. In September, Pfizer was the driving force behind a pledge by nine vaccine companies to “stand with science” and not put forward anything that had not been properly vetted.
Earlier this month, he published an open letter to employees that said he “would never succumb to political pressure” and expressed disappointment that “we find ourselves in the crucible of the U.S. presidential election.”
A small college in Central New York is sending most of its students home, possibly for the rest of the fall semester, because of a sudden coronavirus outbreak that has been traced to a single off-campus party on Oct. 3, college officials said on Friday.
Keuka College, which had experienced just one case of coronavirus during its first six weeks of classes, now has 55 active cases, most of which have been linked to the party.
The school has asked most of its 1,100 students to leave campus this week, urging them to isolate themselves as best they can for two weeks once they get home. Though the school has left open the possibility of allowing some students to return before the Thanksgiving break, the college president, Amy Storey, said “the bar is set very high.”
About 250 students will remain on campus because they have tested positive or have come into close contact with someone who has; are showing Covid symptoms; or have an unstable home situation.
“We had hoped this step wouldn’t be necessary,” Ms. Storey said in a statement, “but the quickly escalating number of positive cases has made this temporary shut-down unavoidable.” She added that the school was compelled to send students home because its small campus lacked sufficient housing to isolate the growing number of infected and possibly infected students.
Like most American colleges, Keuka had planned to send students home for the semester around Thanksgiving, to reduce the kind of travel that often spreads the virus. But in sending them home , it may be providing a preview of what other colleges are likely to face as infections rise across the country.
The New York Times has identified more than 178,000 confirmed cases at colleges and universities since the pandemic began, most of those cases being reported since students began returning to campuses in August.
In an interview, Ms. Storey said the college has been testing only symptomatic individuals, without conducting the kind of random surveillance testing experts say is needed to spot outbreaks swiftly. The strategy seemed to be working up until about 85 to 100 students attended the Oct. 3 party, Ms. Storey said.
Though a number of students who have “flouted” the guidance and rules, the vast majority of students have complied, “which is what makes this situation so tragic,” she said.
Remdesivir, the only antiviral drug authorized for treatment of Covid-19 in the United States, fails to prevent deaths among patients, according to a study of more than 11,000 people sponsored by the World Health Organization.
The drug was granted emergency authorization by the Food and Drug Administration on May 1 after a trial by the National Institutes of Health found that remdesivir modestly reduced the time to recovery in hospitalized. President Trump received the antiviral after he began showing symptoms earlier this month.
“This puts the issue to rest — there is certainly no mortality benefit,” said Dr. Ilan Schwartz, an infectious-disease physician at the University of Alberta in Canada.
But other scientists said the design of the W.H.O.’s sprawling clinical trial, which collected data from hundreds of hospitals, meant the conclusions were not definitive.
Conducted in dozens of countries with various health care systems and inconsistent treatment protocols, the data are difficult to analyze and compare, said Dr. Peter Chin-Hong, an infectious-disease expert at the University of California, San Francisco.
The findings, which were posted online on Thursday, have not yet been peer-reviewed or published in a scientific journal.
The W.H.O.’s study, called the Solidarity trial, enrolled 11,266 adults with Covid-19 in 405 hospitals in 30 countries. The participants were given four drugs singly or in combination: remdesivir, hydroxychloroquine, lopinavir, interferon or interferon plus lopinavir. About 4,100 received no drug treatment.
In the end, no drug or combination reduced mortality, the chances that mechanical ventilation would be needed, or time spent in the hospital, compared with the patients who were not given drug treatment.
Still, several experts noted that some of the drugs in the trial may benefit people with Covid-19 earlier in the course of their illness.