Covid-19 Live Updates: C.D.C. Changes Testing Guidance to Exclude People Without Symptoms, Worrying Experts

The C.D.C. changes testing guidelines to exclude those exposed to virus who don’t exhibit symptoms.

The Centers for Disease Control and Prevention quietly modified its coronavirus testing guidelines this week to exclude people who do not have symptoms of Covid-19 — even if they have been recently exposed to the virus.

Experts questioned the revision, pointing to the importance of identifying infections in the brief window immediately before the onset of symptoms, when many individuals are thought to be most contagious.

Models suggest that about half of transmission events can be traced back to individuals still in the so-called pre-symptomatic stage, before they have started feeling ill — if they ever feel sick at all.

A more lax approach to testing, experts said, could delay crucial treatments, as well as obscure the coronavirus’s true spread in the community. Case numbers remain persistently high across much of the United States, though they have been falling in recent weeks, to an average of about 43,000 new cases a day from a peak of more than 66,000 a month ago. Many of the states that saw the largest outbreaks in early summer are now reporting sustained progress, including Arizona and Florida. But parts of the Midwest, as well as Hawaii and some U.S. territories, are still seeing increases in new cases.

“This is potentially dangerous,” said Dr. Krutika Kuppalli, an infectious disease physician in Palo Alto, Calif. Restricting testing to only people with obvious symptoms of Covid-19 means “you’re not looking for a lot of people who are potential spreaders of disease,” she added. “I feel like this is going to make things worse.”

Prior iterations of the C.D.C.’s testing guidelines struck a markedly different tone, explicitly stating that “testing is recommended for all close contacts” of people infected with the coronavirus, regardless of symptoms. The agency also specifically emphasized “the potential for asymptomatic and pre-symptomatic transmission” as an important factor in the spread of disease.

The C.D.C.’s newest version, which was posted on Monday, amended the agency’s guidance to say that people who have been in close contact with a person with the coronavirus — typically defined as being within 6 feet of that person for at least 15 minutes — “do not necessarily need a test” if they do not have symptoms. Exceptions, the agency noted, might be made for “vulnerable” individuals, or if health care providers or state or local public health officials recommend testing.

“Wow, that is a walk-back,” said Susan Butler-Wu, a clinical microbiologist at the University of California’s Keck School of Medicine. “We’re in the middle of a pandemic, and that’s a really big change.”

Dr. Butler-Wu said she’s concerned that the guidelines would be misinterpreted as implying that people without symptoms were unable to pass the coronavirus to others — a falsehood that experts have been trying for months to dispel.

The reason behind the shift in testing recommendations remains unclear. In response to an inquiry from The New York Times, a representative for the C.D.C. directed the questions to the Department of Health and Human Services. An H.H.S. spokesperson said that “the decision to be tested should be one made in collaboration with public health officials or your health care provider based on individual circumstances and the status of community spread.”

The Trump administration ordered hospitals to report data to H.H.S. or risk losing funding.

The Trump administration on Tuesday threatened hospitals with revoking their Medicare and Medicaid funding if they do not report coronavirus patient data and test results to the Department of Health and Human Services.

The threat was included in new emergency rules, announced by the Centers for Medicare and Medicaid Services, that make mandatory what has until now been a voluntary program.

The new rules generated an immediate backlash from the American Hospital Association, which branded them a “heavy-handed regulatory approach” that was “announced in final form without consultation, or the opportunity to provide feedback.”

Rick Pollack, the association’s president and chief executive officer, called the changes “disturbing.”

“It’s beyond perplexing why CMS would use a regulatory sledgehammer — threatening Medicare participation — to the very organizations that are on the front lines in the fight against Covid-19,” Mr. Pollack said in a statement. “This rule should be reversed immediately.”

The rules come amid controversy over the current voluntary data reporting system. In July, the administration abruptly ordered hospitals to stop reporting coronavirus patient information to the Centers for Disease Control and Prevention and send results instead to a private vendor, Pittsburgh-based TeleTracking Technologies, which provides the data to H.H.S.

That move has raised concerns among public health experts and Democrats on Capitol Hill, who worry about scientific integrity and object to sidelining government experts.

Administration officials say the switch was necessary to improve reporting of testing data, and the rules issued Tuesday will give the administration an enforcement stick.

“Hospitals will face possible termination of Medicare and Medicaid payment if unable to correct reporting deficiencies,” Tuesday’s announcement states.

The hospital reporting requirement is part of what the centers described as “sweeping regulatory changes” intended to better track and combat the coronavirus pandemic. The new rules also require nursing homes to test staff and offer testing to residents for the virus.

The agency said it would soon announce guidance for the frequency of nursing home staff testing, which will be based on the degree of Covid-19 spread in individual communities.

Nursing homes are already required to offer tests to residents when there is an outbreak or other residents show symptoms. Like hospitals, nursing homes will face penalties for noncompliance. They will be inspected and those cited “may face enforcement sanctions” such as “civil money penalties in excess of $ 400 per day, or over $ 8,000 for an instance of noncompliance,” the announcement said.

“These new rules represent a dramatic acceleration of our efforts to track and control the spread of Covid-19,” Seema Verma, the administrator of the centers, said in a statement.

“Reporting of test results and other data are vitally important tools for controlling the spread of the virus and give providers on the front lines what they need to fight it.”

At the Republican National Convention, Melania Trump acknowledges the pandemic’s human toll.

In a speech that struck a strikingly different tone from others at the Republican National Convention, the first lady, Melania Trump, on Tuesday acknowledged the pandemic’s human toll and praised the efforts of front-line medical personnel and other essential workers.

In her speech from the Rose Garden at the White House, Mrs. Trump called Covid-19 an “invisible enemy” that had swept across the nation. She also extended her sympathies to those were ill or who had lost loved ones.

“I know many people are anxious and some feel helpless,” she said. “I want you to know: You’re not alone. My husband’s administration will not stop fighting until there is an effective treatment or vaccine available to everyone.”

“Donald will not rest until he has done all he can to take care of everyone impacted by this terrible pandemic,” she added.

So far, most of the convention speakers who mentioned the pandemic have referred to it in the past tense and rarely mentioned its national toll. As of Tuesday evening, more than 5.7 million people in the United States have been infected with the coronavirus and at least 178,300 have died, according to a New York Times database.

The tone of Mrs. Trump’s remarks also stood in contrast to her husband’s focus on defending his response to the virus and pinning the blame for it on China, while tending to mention the lives lost as an afterthought.

Mrs. Trump spoke moments after Secretary of State Mike Pompeo delivered a shorter and harsher speech, from a rooftop in Jerusalem, that was more in line with the president’s rhetoric on the pandemic. Mr. Pompeo, who is among the administration’s leading China hawks, argued that Mr. Trump had “pulled back the curtain on the predatory aggression of the Chinese Communist Party,” including its handling of the coronavirus.

“The president has held China accountable for covering up the China virus, and allowing it to spread death and destruction in America and around the world,” Mr. Pompeo said at one point. “And he will not rest until justice is done.”

Earlier in the night, Larry Kudlow, the president’s top economic adviser, boasted that President Trump had led an “extraordinary rescue” to “successfully fight the Covid virus” and save the U.S. economy. He failed to mention that the virus was still raging and glossed over the immense unemployment and economic pain that the crisis has created.

‘No second chances’: Colleges are coming down hard on students who violate virus restrictions.

As colleges and universities across the country grapple with rising coronavirus cases, they are increasingly disciplining newly returned students for violating pandemic safety rules, and pressuring fraternities and sororities to stop holding events that violate bans on partying.

At the Ohio State University, 228 students have received interim suspensions for violating rules against large gatherings during the pandemic, the university said on Tuesday. Most of the students were living off campus, and have been asked to remain away from campus until their cases have been adjudicated; some of the suspensions have already been reversed. Violators who live on campus could lose their university housing if their cases are deemed serious enough, the school said.

Montclair State University in New Jersey, which reopened its dorms this month and began classes Tuesday, said it had already suspended 11 students from living in university housing for gathering without masks or social distancing.

“Please understand, there will be no second chances,” school officials warned students in an email message sent over the weekend (not a text message, as an earlier version of this item said). “Any student who violates the safety protocols will be immediately suspended from housing (possibly for the remainder of the year), will be referred to the director of student conduct for disciplinary action and will be immediately de-registered from any courses or programs that have an on-campus component.”

Syracuse University suspended 23 students last week after a gathering on the campus quad that the dean of students decried as “incredibly reckless.” Thirty-six students were suspended by Purdue University after a party at a cooperative house. Penn State University suspended a fraternity for holding an unsanctioned social, and Drake University banned at least 14 students from campus for two weeks for partying.

In Florida, the president of the University of Miami, Julio Frenk, said the school had begun evicting students from dorms for violations, warning in a video that the university — which has had 141 cases since the start of the school year — would continue to monitor student behavior on and off campus.

Outbreaks have emerged at campuses across the country as students have streamed back for fall classes. Many have been linked to large gatherings that were held despite state, local and campus public health rules. Among the recent reports: 566 cases among students, faculty and staff at the University of Alabama, most of them on its Tuscaloosa campus, where classes resumed last week, and 43 new cases at the University of Southern California, which is holding online classes but giving students limited access to campus.

All told, The New York Times has identified more than 23,000 cases on 750 campuses since the coronavirus crisis began in the late winter and spring.

In other education news:

• To help improve poor ventilation in New York City’s aging public school buildings, the mayor said Tuesday that city inspectors would assess every classroom by Sept. 1. and not allow the inadequately ventilated ones to reopen. About 10,000 portable air filters will be installed in nurses’ offices, isolation rooms and other high-risk areas, he said. The powerful teachers’ union has demanded that the city update ventilation systems before the scheduled start of classes in a hybrid model on Sept. 10, but many principals and teachers say they do not believe the buildings will be ready by then and have urged the mayor to push the start of in-person reopening back a few weeks.

Kim Jong-un acknowledges ‘shortcomings’ in North Korea’s fight against Covid-19.

​North Korea’s leader, Kim Jong-un, has urged his government to eliminate “shortcomings” and “​defects” in its battle against Covid-19 and to brace for a typhoon that is approaching the Korean Peninsula, state media reported on Wednesday.

Mr. Kim convened the ruling Workers’ Party’s Political Bureau and its Executive Policy Council on Tuesday, a week after making a rare admission that his five-year economic plan had faltered in the face of​ international sanctions, the coronavirus and recent flood damage.​ North Korea plans to hold a party congress in January to chart a new five-year economic plan.

​During this week’s meetings, Mr. Kim cited “facts about some shortcomings in state emergency anti-epidemic work” and ordered active measures “to overcome the defects urgently,” the North’s official Korean Central News Agency reported on Wednesday, without elaborating.

North Korea has reported no coronavirus infections, but outside experts are skeptical, citing the country’s decrepit public health system and its proximity to China, where the virus was first detected.

Last week, South Korea’s National Intelligence Service told lawmakers in Seoul that the North’s fear of the virus had deepened since July, forcing the authorities to tighten travel in and out of Pyongyang, the North’s capital, and western and southern provinces.

The South Korean spy agency also said that the North’s foreign currency reserves had diminished as United Nations sanctions and the pandemic slashed its exports to China, its main trading partner, according to lawmakers who were briefed by the agency. Budget constraints have so far forced Mr. Kim to scale back his construction projects and reduce his military’s summer field exercises by up to 65 percent, they said.

Another strain on the North’s economy has been an unusually long monsoon season that caused extensive damage to farmland earlier this month. A fresh storm, Typhoon Bavi, is now expected to hit later this week, raising fears that back-to-back natural disasters could wreak further economic havoc.

The United States Department of Agriculture’s Economic Research Service estimated this month that about six in ten North Koreans are food-insecure in 2020.

On Tuesday, Mr. Kim urged his government to “thoroughly prevent the casualties by typhoon and minimize the damage to the crops,” saying that the typhoon will decide “whether we would successfully wrap up this year’s farming or not.”

Mr. Kim’s father, Kim Jong-il, ruled through his inner circles, but his son has convened party meetings more frequently, in an apparent attempt to make his government look more transparent. So far this year, the party’s Political Bureau has met seven times.

“The situation in North Korea must be dire for Kim Jong-un to hold so many high-level conferences,” said Leif-Eric Easley, a professor of international studies at Ewha Womans University in Seoul. “The party does not want to appear flat-footed and will take credit if a crisis is averted.”

U.S. ROUNDUP

Protesters against virus restrictions pour into the Idaho State Capitol.

Conservative protesters flooded the Idaho State Capitol in Boise this week, many of them without wearing masks, to express anger and frustration during a special legislative session called to address voting and liability laws amid the pandemic.

Among the protesters was Ammon Bundy, once the leader of an armed takeover of an Oregon wildlife refuge, who was arrested by Idaho State Police along with two other people for trespassing Tuesday amid protests over coronavirus regulations.

The discontent in Idaho reflects a strong libertarian streak in the rural West. Mr. Bundy and others, including some Idaho public officials, have complained for months about the efforts of state leaders like Gov. Brad Little, a Republican, to rein in the spread of the virus with stay-at-home orders and restrictions on businesses.

“The Idaho people are more than capable of keeping themselves safe,” Mr. Bundy told lawmakers on Monday, according to a report in The Idaho Press. “They are more than capable of driving the greatest economy that any state has enjoyed.”

On Tuesday Mr. Bundy and two others refused to leave an auditorium at the Idaho state capital, long after the hearing had finished, according to a spokeswoman for the Idaho State Police. Mr. Bundy refused to stand so police handcuffed him and wheeled him out in a chair, she said. Early in the afternoon Mr. Bundy told the Idaho Press he was going to remain seated in protest of the removal of “citizen journalists” from a hearing; at least one worked for a libertarian organization.

On Monday police also scuffled with protesters, who shattered a glass door at the State Capitol according to The Idaho Statesman.

Idaho, like many states, saw a sharp increase in new coronavirus cases starting around mid-June. Daily reports of new cases have receded a bit since then, but remain much higher than the figures reported in the spring.

Elsewhere in the United States:

• Gov. Andrew M. Cuomo said Tuesday that New York will now require travelers from Guam to quarantine for 14 days, an addition to a list of 28 states as well as Puerto Rico and the U.S. Virgin Islands. New Jersey also said travelers from those 31 places were subject to a 14-day quarantine, though the state has said compliance is voluntary but expected. Alaska, Arizona, Delaware, Maryland and Montana were removed in the weekly update.

• In New York City, Sheriff Joseph Fucito on Tuesday said officials are considering boarding long-haul buses before passengers disembark at bus terminals, as part of a move by the city to promote compliance with the state’s 14-day quarantine requirement for many travelers. In an interview, Mr. Fucito said officials would randomly target buses whose public schedules indicate they are coming from places on the state’s list. Upon the buses’ arrival, but before passengers can offload, officials would board the bus and ask riders to fill out the state’s required travel form with their contact information and quarantine plans.

• American Airlines plans to furlough 19,000 employees this fall when restrictions on job cuts that airlines agreed to in exchange for federal aid end on Oct. 1. This brings the total number of employees cut to 40,000 when combined with employees who have taken buyouts or agreed to long-term leave. In a letter to employees, the top two executives blamed Congress for not providing enough aid to the airline industry.

• American Airlines also received approval from the Environmental Protection Agency to use a new cleaning spray on its planes that purports to kill coronaviruses on surfaces for up to seven days. The agency described the product, Allied BioScience’s SurfaceWise2, as groundbreaking and a “first-ever long-lasting antiviral product.” American said it would start using SurfaceWise2 in the coming months.

• Mississippi reported 67 new deaths and Montana reported 6 new fatalities, each setting single-day state records.

• Miami-Dade County, Fla., which has been hit hard by the virus, will allow indoor restaurant dining starting Monday, Mayor Carlos Gimenez said Tuesday. The decision was made after consulting with restaurant owners, the White House coronavirus task force and local medical experts, he said. The county’s positivity rate has been just under 10 percent for about a week, which is still higher than the 5 percent that Mr. Gimenez had said would be the target for more widespread reopening. Restaurant capacity will be capped at 50 percent, with no more than six people at a table. Tables will be spaced, doors must be kept open — windows too, if possible — and the air-conditioning must run all the time. Masks will be required for diners until they are served water and any time they get up from the table. Mr. Gimenez also said he does not plan to close beaches for Memorial Day, as the county did for the Fourth of July. His administration plans to deploy more personnel to enforce coronavirus rules on the beaches and elsewhere in the county during the holiday weekend, he said.

• Most children born in New Jersey would be entitled to a $ 1,000 state-financed nest egg under a proposal that Gov. Philip D. Murphy said Tuesday could narrow a widening wealth gap in the U.S., where the average white family has seven times the wealth of the average Black family. The move would be a small but tangible step, the governor said, toward confronting inequities that have been brought into particularly stark relief by the pandemic: Black and Latino people have died and lost jobs at far higher rates than white people. The State Legislature recently approved nearly $ 10 billion in bond debt to cover the extraordinary costs created by the pandemic and a related drop in tax revenue.

  Mr. Murphy, who is again proposing a so-called millionaire’s tax, said the baby-bond initiative would be coupled with $ 1.2 billion in cuts across state agencies. He also proposed raising cigarette taxes to $ 4.35 a pack, the highest in the nation; and increasing sales taxes on boats, yachts and firearms, among other measures.

• Given the complexity of state tax laws, accountants are advising their clients to track the number of days they spend working out of state. Some states impose income tax on people who work there for as little as a single day.

Global ROUNDUP

Two more cases of reinfection were reported, this time in Europe.

Two more cases of reinfection with the coronavirus were reported in Europe on Tuesday, a day after a 33-year-old man in Hong Kong was confirmed to have been infected a second time.

In all three cases, researchers compared genetic material from both rounds of infection and confirmed that the patients were not just carrying remnants of dead virus left over from the first illness.

The new cases were announced by European researchers. The data have not been published in any form as yet.

Experts told The Times on Monday that reinfections with the virus are not surprising, though not believed to be common. As with most other respiratory viruses, including common-cold coronaviruses and influenza, one bout with the new coronavirus may provoke an immune response that may not prevent a second infection — but nonetheless is likely to mute symptoms the second time around.

One new reinfection case was an older person in the Netherlands with a weakened immune system, researchers said. The other patient, in Belgium, was a woman who had only mild symptoms in March and became infected again in June.

The man in Hong Kong, too, had only mild symptoms and did not develop detectable antibodies after the first infection. Even so, he had no symptoms at all the second time and his case was found only by routine screening at an airport. His case suggests that even people who did not produce a strong antibody response to an initial case may be protected from becoming seriously ill if exposed to the virus again, experts have said.

Some news reports have speculated that the cases raise questions about the effectiveness of vaccines for preventing coronavirus infection. But experts have said the opposite: Vaccines can be designed to elicit immunity that’s stronger and longer lasting than that resulting from natural infection.

“In order to provide herd immunity, a potent vaccine is needed to induce immunity that prevents both reinfection and disease,” Akiko Iwasaki, an immunologist at Yale University, told The Times on Monday.

In other news from around the world:

• South Korea said it was again closing schools and switching back to online classes for students in the Seoul metropolitan area, as the country reported 280 new cases on Tuesday, the 12th-straight day of triple-digit daily increases in virus infections.

• As Hong Kong on Tuesday announced plans to begin easing its social-distancing rules, the city’s leader, Carrie Lam, said that criticism by health experts of a new, Beijing-backed coronavirus testing program was a “politically calculated” effort to smear the Chinese government. Some of those experts say the plan is a waste of resources, while activists fear it could lead to the harvesting of DNA samples for China’s surveillance apparatus, accusations that local officials deny.

• The Chinese government has imposed a sweeping lockdown across the Xinjiang region in western China, penning in millions of people as part of what officials describe as an effort to fight a resurgence of the coronavirus. But many residents accuse the government of acting too harshly, reviving concerns about human rights abuses in Xinjiang. The Chinese government has spent years perfecting a system of mass surveillance and control in the region and has long imposed draconian social rules on the region’s largely Muslim ethnic minority groups, who make up about half the population.

• Two Irish political leaders have resigned after a furor, now known as “GolfGate,” over their attendance at a dinner organized by the Golf Society of the country’s legislature. The gathering took place a day after the government tightened coronavirus restrictions to combat a spike in infections, and has sparked a backlash that has also threatened the jobs of other public figures, including the European Union’s trade commissioner, Phil Hogan.

• Uganda has recalled its ambassador to Denmark as well as her deputy after allegations that they were plotting to steal funds allocated to deal with the pandemic. The ambassador, Nimisha Madhvani, and her deputy, Elly Kamahungye, were recorded devising ways to share the money along with other embassy staff members. Uganda’s Ministry of Foreign Affairs called the allegations “grave” and said it would carry out a “thorough investigation” into the matter.

A February conference in Boston led to the infection of tens of thousands around the world, a study shows.

Scientists have found that a conference in Boston in late February triggered a gigantic spread of the virus. It ultimately may have led to the infection of tens of thousands of people both in the United States and abroad.

The finding emerged from a large study of the outbreak in the Boston area, which the authors posted online on Tuesday but has not yet been published in a scientific journal.

Researchers at the Broad Institute of Harvard and the Massachusetts Institute of Technology analyzed the genomes of coronavirus samples taken from 772 people diagnosed with Covid-19 between January and May. They collected the virus from samples taken at hospitals, nursing homes, homeless shelters and other locations in the Boston area.

The researchers found, by analyzing variations in samples of the coronavirus, that it was introduced more than 80 times to the region — mostly from Europe, and coming either directly to Boston or indirectly through other parts of the northeastern United States. Most of these introductions petered out without much spread.

But a conference hosted by the biotech company Biogen on Feb. 26 and 27 fueled the spread of one strain of the virus, which soon became very common around Boston. The researchers were able to trace it later to other states and to countries such as Singapore and Australia.

Dr. Jacob Lemieux, the first author of the study and a physician at Massachusetts General Hospital, said in an interview that it was just a matter of bad luck that someone with the virus spent time in a place that could promote its spread — and that the infected people promptly boarded airplanes to spread the virus further.

“It’s the play of chance,” said Dr. Lemieux. “If it hadn’t been this conference, it would have been another event.”

Send children to school? Democrats are more reluctant than Republicans, a survey finds.

Parents as a whole are stressed and anxious about the virus and the school year. But there’s a large political divide, a new survey for The New York Times shows. Democrats are more reluctant to send their children to school than Republicans are, and are more worried about their families becoming infected.

Republicans are also more likely to say teachers should work in person, according to the survey, which was administered by Morning Consult to a nationally representative sample of 1,081 parents from Aug. 4 to Aug. 8.

President Trump made school reopenings a contentious issue when, in July, he demanded that schools open, even as cases were rising. It ended up alienating many teachers and parents, who said he wasn’t doing what was necessary to reopen safely. But it did not turn away his loyal supporters, the new data indicates.

When parents who approve of the job Mr. Trump is doing were asked whether they had considered keeping their child home from school for health and safety reasons, even if it reopened, 29 percent said they had considered it. Among parents who disapprove of Mr. Trump, 45 percent considered keeping their children home.

There was a similar divide when parents were asked whether teachers should be expected to return to school in person — a question that has catalyzed teachers’ unions and in some cases, divided teachers, administrators and parents. Over all, one-quarter of parents said teachers should be strongly encouraged to return, two-thirds said they should be able to do their jobs virtually, and the rest weren’t sure.

Republican parents were nearly three times as likely as Democrats to say teachers should be considered essential workers who needed to return to school. Thirty-six percent of Republicans said that, compared with 13 percent of Democrats.

Flu-season testing delays in the U.S. could make it easier for the virus to spread undetected.

Come fall, the rise of influenza and other seasonal respiratory infections could exacerbate already staggering delays in coronavirus testing, making it easier for the virus to spread unnoticed, experts said.

In typical years, doctors often don’t test for flu, simply assuming that patients with coughs, fevers and fatigue during the winter months are probably carrying the highly infectious virus. But this year, with the coronavirus bringing similar symptoms, doctors will need to test for both viruses to diagnose their patients, further straining supply shortages.

Testing for individual viruses poses many challenges for doctors and laboratory workers already fighting their way through supply shortages. Several of these tests use similar machines and chemicals, and require handling and processing by trained personnel.

Some manufacturers have begun making tests that can screen for several pathogens at once. But these combo tests are expensive and will likely make up only a small fraction of the market.

“The flu season is a bit of a ticking time bomb,” said Amanda Harrington, the medical director of microbiology at Loyola University Medical Center. “We are all waiting and trying to prepare as best we can.”

Flu viruses and coronaviruses differ in many ways, including how they spread, how long they linger in the body and the groups they affect most severely. Food and Drug Administration-approved antivirals and vaccines exist for the flu, but no such treatments exist for the coronavirus, which has killed at least 812,000 people worldwide in less than a year, according to a Times database.

Being infected with one virus doesn’t preclude contracting the other. And researchers also don’t yet know how risky it is for a person to harbor both viruses at the same time.

Those differences make it essential to tease the two pathogens apart, as well as to rule out other common winter infections like respiratory syncytial virus, or R.S.V., which hits the very young and very old especially hard.

But many flu and R.S.V. tests vanished from the market this spring as the companies that make them rapidly pivoted to address the coronavirus.

After a sharp case rise in Danbury, Conn., the mayor says ‘we want to make sure that we can slow the spread.’

Facing an uptick in cases, the city of Danbury, Conn., has closed public boat launches to prevent the spread of the virus among boaters on a popular lake, Mayor Mark Boughton said on Tuesday.

Connecticut has also closed a boat ramp it operates nearby, in an effort to curb parties held on the water or in nearby parking lots, Gov. Ned Lamont said at a news conference with the mayor.

“We want to make sure that we can slow the spread,” Mr. Boughton said.

On Friday, officials in Connecticut issued a public health warning for Danbury, a city of about 84,000 people near the New York border, that urged residents to stay home when possible and limit gatherings. The move came after 178 new cases were reported in the city in the first 20 days of August, more than quadruple the figure for the prior two weeks.

In response, Danbury’s public schools will reopen with remote learning on Sept. 8 and will re-evaluate on Oct. 1 whether to allow some in-person learning.

So far, public health officials have linked the cases to domestic and international travel, live services held at places of worship and contact on athletic fields, Mr. Boughton said. They also remained concerned over large family gatherings. As of Tuesday, travelers to Connecticut are now required to quarantine for 14 days if they are coming from Guam, as well as dozens of states and two other territories.

Mr. Lamont said that the uptick had not spread to parts of Connecticut beyond Danbury.

A state legislator, David Arconti, said that cases appeared to have risen in neighborhoods of Danbury that lost power for days after Tropical Storm Isaias ripped through the New York region. He and other officials were exploring a possible connection, he said.

Mr. Lamont said the state would monitor other municipalities that had been hard hit by power outages to see if they saw an uptick similar to Danbury’s.

Reporting was contributed by Sarah Almukhtar, Gillian R. Brassil, Alexander Burns, Stephen Castle, Choe Sang-Hun, Abdi Latif Dahir, Richard Faussett, Sheri Fink, Michael Gold, Jenny Gross, Javier C. Hernández, Shawn Hubler, Mike Ives, Annie Karni, David Leonhardt, Apoorva Mandavilli, Jonathan Martin, Tiffany May, Patricia Mazzei, Claire Cain Miller, Heather Murphy, Eshe Nelson, Amelia Nierenberg, Adam Pasick, Elian Peltier, Monika Pronczuk, Dana Rubinstein, Eliza Shapiro, Mitch Smith, Eileen Sullivan, Katie Thomas, Tracey Tully, Katherine J. Wu and Elaine Yu, Carl Zimmer.