Coronavirus cases are surging again in Europe after months of relative calm, but the second wave looks different from the first: Fewer people are dying, and the newest and mostly younger victims of the pandemic need less medical treatment.

Unlike the initial hit of the pandemic this spring, which overwhelmed hospitals and turned nursing homes into grim mortuaries, the European resurgence of recent weeks has not forced as many people into medical wards.

But the increase is widespread, and it is unsettling societies that had hoped the worst was behind them. Paris on Friday joined some other French jurisdictions in imposing a citywide mask requirement, with cases spiking. France, Germany, Spain and others posted caseloads in recent days that had not been seen since April and early May. Spain has been hit particularly hard, with per capita cases now worse than in the United States — a notable marker in Europe, which after the initial springtime spike had generally controlled the virus more successfully than America.

And with almost every European country planning a return to in-person schooling, many starting next week, public health officials are holding their breath for the impact.

The surge is a first test of the efforts Europe has made to improve its resilience in the half-year since the pandemic unleashed a wave of suffering across the world. Most European countries have improved their testing capacity. They have hired contact tracers to combat big outbreaks. They have masks and gloves for their doctors and nurses. And as summer travelers return home and classes resume, experts and leaders say they hope to be able to avoid bigger lockdowns in the coming months.

Many countries, including Italy, endured grinding lockdowns this spring. Now citizens are exhausted, and economies are still flagging.

“I don’t think the country can survive another lockdown. And to be frank, there is no reason to,” said Ranieri Guerra, a World Health Organization assistant director general who is advising the Italian Health Ministry. “It’s very unlikely we’ll see anything like it was in the past. The likely scenario is that we’ll have some clusters here and there, even heavier than now, but very localized.”

Italy was ravaged by the virus in the spring. And now it is seeing something of a resurgence. On Friday, it reported 1,469 new cases, the biggest increase in a 24-hour period since it was emerging from lockdown in early May. In Italy, many of the new cases have been tied to travels abroad. Over the past month, the average age of a person who tested positive was 31. Throughout March, it was above 60.

Italian officials say that hospitals and nursing homes are better prepared and treatments more advanced. Though some Italians have dropped their guard, older people in particular remain cautious, wearing masks outdoors and staying away from crowds.

But Guerra said that containment depends on contact tracing and testing.

“If you don’t have a system to track, trace and quarantine localized clusters, it’s really difficult. This virus is very contagious,” he said. “Moving from 100 cases to 200 may take a few days, but moving from 2,000 to 4,000 may take hours.”

At least part of the surge in cases may stem from testing that is far more widely available than it was in the spring. Younger people who have moderate symptoms are being encouraged to get tested, unlike in March, when only those who were sick enough to be hospitalized qualified for a test in most countries.

“In February, in March, we had no clue what was circulating. We were only seeing the tip of the iceberg,” said Steven van Gucht, the head of viral diseases at Sciensano, Belgium’s national public health institute. “Now we are trying to see the iceberg and to adapt our behavior accordingly.”

But with summer fading into fall, questions remain about how long the virus can spread among younger people before it spreads to more-vulnerable older generations.

Belgium had one of the world’s worst per capita death rates this spring, with most of the mortality occurring in nursing homes. Now, even though cases have nearly quintupled compared with their lowest point in late June, Belgian hospitals remain calm. Very few cases are appearing in nursing homes, and 40 percent of new cases have been diagnosed among people between ages 20 and 40.

During the first wave, anti-pandemic measures in most European countries were far more stringent than in the United States. In some countries, police officers fined people for venturing past their front doors. The measures lasted for months. The payoff was that by early June, the virus had been brought under control in most countries across the continent.

This time, the European approach seems more American: decentralized, localized, a hodgepodge of individual measures that policymakers hope will add up to a pandemic that is kept in check. In Belgium and France, for example, mask-wearing is now required in many cities facing a second wave. Belgian authorities earlier this month asked citizens to drastically curtail their social interactions, limiting their close household contacts to a “bubble” of just five other people.

Whether that will be enough remains an open question.

“It’s a bit too early to be too complacent about ourselves, whether we have found the magic formula,” van Gucht said. “Maybe I can tell you after next winter whether this still will work.”

Among European countries, Spain presents the most ominous picture. It is reporting nearly as many daily cases as it did in March, when it suffered as acutely as any country on the continent.

Experts say the country has squandered many of the gains from its springtime lockdown by reopening too quickly — without building up the deep network of contact tracers used in other Western European countries. Epidemiologists say Spain’s latest cases largely stem from the kind of activities that the government had banned early in the pandemic: family gatherings, celebrations, dancing at nightclubs.

“We moved very fast to reopen, and the virus was still circulating too [widely] in order to achieve a sustained reduction of cases,” said Antoni Trilla, dean of the University of Barcelona Medical and Health Sciences School.

But the country is hoping that this increase won’t hit with the same tragic force as the first wave. The new cases have been detected largely among the young. Coronavirus hospitalizations, despite having quadrupled over the past month, remain manageable for the health system. In Madrid, 13.6 percent of hospital beds are occupied by coronavirus patients; in March the city’s hospitals were full.

The country’s prime minister, Pedro Sánchez, has rejected the idea of a new national lockdown and said that conditions and knowledge of the virus have improved since the spring. Short of a lockdown, smaller measures have been taken, including the closure of nightclubs. The Madrid region has delayed the return to school for some students and further reduced its planned class sizes.

But it is unclear whether those measures can prevent the virus from leaping to older generations when young, infected people return to their homes. Trilla said it would be “difficult” but necessary to use targeted measures to keep the virus at bay.

“We have to look at the local situation and move with surgical precision to close some schools, to isolate certain areas for a while,” Trilla said.

In France, meanwhile, the government on Friday recorded a spike of 7,379 new cases in the past 24 hours — the second-largest ­single-day caseload since the pandemic began and the latest data point in an upward swing that began last month. Friday’s number was up more than a third from the already high figure posted just two days earlier.

France imposed one of Europe’s strictest nationwide lockdowns between mid-March and mid-May, and authorities have since said that a second period of closures would be devastating for the economy.

“We’re doing everything to avoid another lockdown and in particular a nationwide lockdown,” President Emmanuel Macron told journalists Friday. But he added: “Nothing can be ruled out.”

In light of the recent case uptick, Prime Minister Jean Castex announced Thursday that the government had prepared a set of new lockdown plans to be deployed if necessary.

Leaders implored citizens to remain vigilant, especially as students return to class on Tuesday, masks in hand.

“Washing your hands, keeping your distance and wearing masks will be our daily life for several months,” said French Health Minister Olivier Véran. “I’m not saying it’s easy — I’m saying we have no choice.”

Harlan reported from Rome and McAuley from Paris.