The coronavirus circulated at the Strugis motorcycle rally, then spilled outward.

Health officials in several states are linking cases of the virus to the 10-day Sturgis motorcycle rally in South Dakota, which drew hundreds of thousands of participants this month in spite of the pandemic.

Kris Ehresmann, the infectious disease director at the Minnesota Department of Health, said at a briefing on Friday that at least 15 cases in Minnesota were identified as having originated from rally attendees. Seven more cases were identified in Nebraska, according to reporting from CNN.

Health officials in South Dakota said this week that they had traced several cases to a popular bar along Sturgis’s main street, where photos showed thousands of people congregating without masks over the course of the rally.

An analysis of the geographical footprint of the rally’s attendees by a company using anonymized cellphone location data showed that the event drew participants from across the country, prompting fears that infections could spread further. The map of migration patterns associated with the rally showed participants traveling to Sturgis from locations across the continental United States, and back.

The rally ended last Sunday, but health officials warn that it will take time before the extent of associated outbreaks can be measured, as it can take days for symptoms to appear in people who have been infected.

Mr. Ehresmann said on Friday that he expected to see more cases recorded as additional information about the outbreak and subsequent contact tracing became available.

India, approaching 3 million cases, adds restrictions but allows some religious gatherings.

As India this weekend approaches a total of three million confirmed coronavirus cases — the third highest globally after the United States and Brazil — the South Asian nation continues its delicate balance between allowing public life like major religious festivals to go ahead while also adding restrictions aimed at thwarting the virus.

The country’s Supreme Court on Friday allowed three Jain temples to open for a two-day festival in Mumbai, the Indian city hit hardest city by the pandemic, raising concern that the religious shrines will become super-spreader sites.

After petitions were circulated by some religious groups, the court had last month advocated the reopening of places of worship, arguing that the livestreaming of rituals was an inadequate substitute for physical visits to the sites.

But many regional governments in the country are continuing to bring in restrictions on public gatherings. In the northern state of Punjab, the chief minister has limited them to no more than four people.

India, a nation of 1.3 billion people, recorded 69,878 new confirmed coronavirus cases on Friday — the fourth consecutive day on which more than 60,000 new cases were added. As of Saturday morning, it had recorded a total of 2,975,700 cases and 55,794 deaths, according to a Times database.

The country was subject to one of the world’s strictest lockdowns starting in late March, with all people ordered to stay inside, businesses closed and public transit halted. But as the measures took a severe economic and social toll, government officials began lifting some restrictions in hopes of easing the suffering.

In recent months, there have been complaints across the country of shortages of hospital beds, and many people have accused the government of not making the most of the gains made during the lockdown.

Coronavirus Schools Briefing: The pandemic is upending education. Get the latest news and tips as students go back to school.

As public markets and other spaces were allowed to reopen with little social distancing, cases began rising in congested localities. Now, India’s confirmed caseload has climbed from two million to nearly three million in just over two weeks.

A big wedding in New York State is blocked at the last minute.

A couple who planned to hold a wedding with 175 guests in western New York State on Saturday had to postpone it after a federal appeals court judge blocked the event, responding to a legal challenge by the state government over the crowd’s expected size.

The ruling, issued on Friday, came two weeks after a lower court said weddings at venues in the state that also function as restaurants where indoor dining is allowed were not subject to a 50-person cap on gatherings that Gov. Andrew M. Cuomo imposed to help fight the coronavirus.

The lower court ruling opened the door for such wedding venues to host parties of more than 50 people under the same rules that apply to restaurants. Those rules now limit indoor service to half a restaurant’s typical capacity.

The lower court’s decision was prompted by a lawsuit filed by two couples who had booked weddings at the Arrowhead Golf Club in Akron, N.Y., about a half-hour’s drive northeast of Buffalo. One of the couples was married the day the ruling was issued. The other was to be married this weekend.

State officials, who have argued in court filings that weddings pose a greater public health risk than indoor dining and are potential “super-spreader” events, immediately appealed the ruling.

On Friday, Judge Denny Chin of the U.S. Court of Appeals for the Second Circuit granted state lawyers’ emergency request to halt the second wedding until a panel of judges could consider their arguments more fully.

Bolivia’s coronavirus death rate is among the world’s worst, an analysis shows.

So many people were dying that it was obvious the government’s numbers couldn’t be accurate. Calls to pick up bodies were inundating the country’s forensic office. By July, agents were gathering up to 150 bodies per day, 15 times the usual amount in previous years, said Bolivia’s chief forensic official, Andrés Flores.

The demand on his office suggested that the official tally of Covid-19 deaths — now just over 4,300 — was a vast undercount, Mr. Flores said. But with limited testing, scarce resources, and a political crisis that is tearing the country apart, the extra lives lost were going largely unrecognized.

The likelihood of underreported cases and death tolls has been a concern in several places, including the United States, as testing kits have been in limited supply and some sick people have avoided hospitals, fearing the prospect of being cut off from loved ones.

But the turmoil in Bolivia appears to have made many of its infected citizens particularly vulnerable to being overlooked.

New mortality figures reviewed by The New York Times suggest that the real Covid-19 death toll there is nearly five times the official tally, indicating that the country has had one of the world’s worst coronavirus outbreaks. The extraordinary rise in deaths there during the pandemic, adjusted for the country’s population, is more than twice as high as that of the United States, and far higher than the increases in Britain, Italy and Spain.

About 20,000 more people — in a country of only about 11 million — have died since June than in past years, according to a Times analysis of registration data from Bolivia’s Civil Registry.

Federal aid and eviction bans have kept many tenants in their homes. That support is ebbing.

Almost from the moment the coronavirus upended the U.S. economy in March, there has been a persistent fear of widespread evictions.

Yet one way or another, through five months of economic dislocation, tenants have generally kept up their rent payments. They’ve done so with government checks and family help, with savings and odd jobs, or with church charity, nonprofit rescue funds and GoFundMe campaigns.

Now, the question is how much longer these patchwork maneuvers will work.

For all of the government’s problems in containing the virus, its financial rescue efforts were largely effective in keeping tenants in their homes. The $2 trillion CARES Act, with its $1,200 stimulus payments and $600 a week in extended unemployment benefits, helped laid-off renters stay current, while federal, state and local eviction moratoriums guaranteed stability for those who could not.

But those efforts have largely lapsed: The $600 payments ended in July, and about 20 states have eviction moratoriums, down from 43 in May. President Trump signed an executive order telling federal agencies to help avoid evictions, but the provisions were vague. Congress has been at an impasse over new aid, and a stopgap $300 weekly unemployment supplement announced by Mr. Trump has reached few workers.

For many tenants, efforts to conserve money and avoid missing rent have caused them to retrench on investments like education, a decision that could limit their futures in the work force and permanently alter the trajectories of their lives.

In Germany, researchers organized a concert to figure out how the virus spreads at big events.

Despite the recent rise of coronavirus infections in Germany, 4,000 people lined up to watch singer-songwriter Tim Bendzko on Saturday in the eastern city of Leipzig.

But this wasn’t another story of an entertainment venue flouting public health concerns in order to get back to business. The daylong show was an experiment set up by scientists to help figure out why mass events are so effective at spreading the virus and how the most risky behaviors could be avoided.

Each of the concertgoers passed a Covid-19 test and had their temperature taken before entering the closed arena. They were also all given trackers to allow researchers to monitor who they came close to, as well as an FFP2 respirator mask to wear and a bottle of special fluorescing hand sanitizer that allowed researchers to learn which areas were most frequently touched.

Researchers from the Martin Luther University of Halle-Wittenberg will spend weeks analyzing the data to determine when and where transmission of the virus was most likely to occur at the venue.

“We want to find out: what are the moments, what are the situations where this risk happens,” said Dr. Stefan Moritz, the lead researcher, in a video statementabout the project, called Restart-19.

On Friday, Germany’s authorities registered 2,034 cases, its highest daily total since the end of April, when the country managed to slow the spread of the virus through a countrywide lockdown.

GLOBAL ROUNDUP

Another threat to the Great Barrier Reef: The pandemic has scared off tourists.

Tour operators in the tropical Australian city of Cairns were already fighting a perception that the Great Barrier Reef is in its death throes as warming waters cause repeated mass bleaching that has robbed many corals of their vivid colors. But where climate change has been more of a creeping threat to the reef’s survival, and thus to Cairns’s tourism, the coronavirus has delivered a hammer blow.

Now this city, so linked with the natural wonder just off its shore that it can scarcely imagine life without the visitors who come in droves, has been forced to confront the prospect that it can no longer depend on tourists.

Foreign and local travelers, already deterred by last summer’s devastating bush fires and now locked out by Australia’s international and domestic travel bans, have all but vanished, and a $4.6 billion industry built around the world’s largest living structure has ground to a near halt.

The sudden disappearance of visitors feels all the more unreal because the virus itself has barely touched Cairns: The city of 150,000 people in far northeastern Australia has recorded only a couple of dozen cases, and currently has none.

But there is no escaping the pandemic’s reach.

In Cairns, visitors who usually cram the jetty every morning as they wait to pile onto boats have dwindled from the thousands to a few hundred, leaving operators out of work, boats moored at the dock, and some hotels and restaurants shuttered.

In other developments around the world:

• South Korea reported 332 new cases on Saturday, the highest daily jump since early March, and fears that an outbreak started in a church in Seoul, the capital, is spreading to the rest of the country. In the past week, the government has banned large gatherings and shut down nightclubs, karaoke rooms and other high-risk facilities in the Seoul metropolitan area. On Saturday, Health Minister Park Neung-hoo said the government would do the same in the rest of the country, starting on Sunday, to fight the spreading epidemic.

Coronavirus in the classroom: Some schools are keeping quiet about infections.

Some U.S. states and school districts provide detailed data on coronavirus outbreaks in schools. Others keep such information under wraps.

On the first day of school in Camden County, Ga., local Facebook groups were buzzing with rumors that a teacher had tested positive. The next day, a warning went out to school administrators: Keep teachers quiet.

“Staff who test positive are not to notify any other staff members, parents of their students or any other person/entity that they may have exposed them,” Jon Miller, the district’s deputy superintendent, wrote in a confidential email on Aug. 5.

In the weeks since, parents, students and teachers in the community have heard by word of mouth of more positive cases linked to district schools. Some parents said they had been called by local officials and told that their children should quarantine.

But even as fears of an outbreak have grown, the district has not publicly confirmed a single case, either to the local community or to The New York Times.

As schools in parts of the country have reopened classrooms amid a still-raging pandemic, some districts have sent weekly — and in some cases daily — reports to families and updated online dashboards with the latest positive test results and quarantine counts. Others districts have been silent, sometimes citing privacy concerns.

State notification polices also vary widely. Officials in Colorado and North Carolina are reporting which schools have had positive cases, while Louisiana, which had not previously identified specific schools with outbreaks, said this week that it was creating a new system to “efficiently report relevant Covid-19 data in schools for greater public visibility.”

On the other end of the spectrum, Oklahoma does not require school districts to report Covid-19 cases to health departments. Tennessee this week backed away from a previous commitment by the governor to report the number of cases linked to schools, and is providing information only by county.

What we learned this week

Herd immunity, Greek life, Venezuela’s crackdown: Here’s the week in coronavirus news.

What if “herd immunity” is closer than scientists thought?

To achieve herd immunity with the coronavirus — the point at which it no longer spreads widely because there are not enough vulnerable humans — scientists have suggested that perhaps 70 percent of a given population must be immune, through vaccination or because they survived infection.

Now some researchers are wrestling with a hopeful possibility. In interviews with The New York Times, more than a dozen scientists said the threshold was likely to be much lower: 50 percent, perhaps even less. If that is true, then it may be possible to turn back the coronavirus more quickly than once thought.

Here are other highlights in coronavirus news from the past week:

• The F.D.A.’s emergency approval of blood plasma is now on hold. U.S. government health leaders including Dr. Francis S. Collins and Dr. Anthony S. Fauci urged caution, citing weak data from the country’s largest plasma study.
• As U.S. universities struggle with reopening amid outbreak, Greek life is posing an especially fraught challenge: how to prevent tightly packed sorority and fraternity houses from turning into virus clusters.
• In Venezuela, a ruined economy and a broken health care system have left President Nicolás Maduro unable to fight the pandemic as other world leaders have. Instead, he has treated the virus as a national security threat and deployed security forces to detain thousands of Venezuelans.
• New York has tamed the virus, but can it hold off a second wave? The sustained low rate of infection has surprised local health officials, though a resurgence may be inevitable, despite the state’s and city’s best efforts.
• Local officials in China hid the dangers of the virus from their leaders in Beijing. A new U.S. intelligence report said top officials in Beijing were in the dark on the true dangers of the virus in early January, because local officials tried to hide the outbreak from the central government. The new assessment adds perspective and context to actions — and inactions — that created the global crisis.

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With Zoom meetings, remote schooling and the rest of the ways people are spending life online, privacy is more important than ever. Here is how to go about securing your computer and information.

Reporting was contributed by Livia Albeck-Ripka, Choe Sang-Hun, Ron DePasquale, Conor Dougherty, Gillian Friedman, Anatoly Kurmanaev, Dan Levin, Allison McCann, Christopher F. Schuetze, Ed Shanahan, María Silvia Trigo and Sameer Yasir.