LONDON — The British government has made a big show this summer about its coronavirus quarantine list — and generated lots of drama.

The ever-growing list of countries identified as virus hot spots has prompted diplomatic outrage from British allies, who threaten reciprocal travel restrictions. It has stirred travel and airline industry leaders to complain that Britain is killing their sectors by hanging up a “closed” sign. And it has set off panicky scrambles of British holidaymakers trying to rush home before mandatory 14-day quarantines take effect.

Prime Minister Boris Johnson said Britain must be “absolutely ruthless about this, even with our closest and dearest friends and partners around the world.”

But the enforcement numbers don’t suggest ruthlessness. Since June, when Britain began requiring self-isolation for people traveling from countries where the novel coronavirus is spreading at a rapid rate, police have fined only three people for ignoring the rules in England and Wales. An additional nine people were fined for failing to fill out contact forms.

That’s out of the 50,000 people the government says arrive from abroad each day, many traveling from countries on the quarantine list.

On paper, the rules are strict. Self-isolators must stay indoors, at a single location, for two full weeks, having food and medicines delivered, with no exceptions and no visitors. The government warns: “You cannot leave your home to walk your dog. You will need to ask friends or relatives to help you with this.”

According to Home Secretary Priti Patel, 99.9 percent of arrivals complied with the quarantine orders.

But a report by Parliament’s Home Affairs Committee said it was “unconvinced” by claims of near-perfect adherence.

“Of course 99.9 percent are not compliant,” said Annelies Wilder-Smith, a professor of emerging infectious diseases at the London School of Hygiene and Tropical Medicine. Public health experts suggest 80 percent compliance might be a more reasonable assumption.

In a rare instance of people being called out — though not fined — for violations, Scottish health authorities reported “a number of cases” of children returning to school last month without quarantining after vacations abroad.

“I must remind you that the law requires everyone returning to Scotland from nonexempt countries to self-isolate at home for 14 days,” National Clinical Director Jason Leitch warned citizens. “This includes children as well as adults.”

On the whole, British officials have taken a “light touch” approach to quarantine enforcement, as the Financial Times called it — or lax, as some critics charge.

Gabriel Scally, a visiting professor of public health at Bristol University, noted that Britain was relatively late to impose border restrictions during the pandemic. In April, the Pew Research Center reported that more than 90 percent of the world’s population lived in countries with travel restrictions. Britain was not among those countries.

Now, the country’s “red list” of countries that require quarantines is much longer than its “green list” of nations that are exempt. But the regulations seem “almost entirely voluntary because they are not enforced,” Scally said.

Other countries have been more hands-on as they grapple with how to keep imported infections at bay.

In Australia, almost all international travelers have to undergo a 14-day quarantine at a designated facility or hotel. Australia has also mostly banned its citizens from leaving the country during the pandemic.

In South Korea, foreign travelers are tested for the coronavirus and required to self-isolate for two weeks at a government-designated facility at their own expense, about $100 to $150 per night.

Germany has begun compulsory coronavirus testing for all travelers arriving at its airports from high-risk countries. At Hong Kong’s airport, arriving passengers are hustled onto a shuttle bus to a testing location.

Britain, meanwhile, has struggled to get a test-and-trace system in place — as a means to contain outbreaks or to monitor new arrivals. The prime minister promised a “world-beating” cellphone app to track and slow infections. Launch has been repeatedly delayed.

Since June, the government has required travelers entering the country to fill out a “passenger locator form,” supposedly to enable public health workers to track them down by phone and confirm they are complying with quarantines.

Border Force police have been doing spot-checks to make sure people have filled out the form online before arrival. Police can issue fines of 100 to 1,000 pounds.

The government said in July that police had done 383,000 checks in the first weeks of the program. During the course of the summer, the Border Force issued nine fines to people who had failed to complete the form.

Even fewer fines have been associated with quarantine violations. Public Health England, which is responsible for monitoring compliance, says its subcontractors are contacting a random sample of 1,000 people a day who have returned from high-risk countries and asking if they’ve been isolating. The trackers attempt to contact people by phoning a maximum of three times over three days.

Alerted to violations through those calls, the National Police Chiefs Council said its officers have issued fines to just three people in England and Wales for violating their quarantines since the policy began in June.

Some countries have been on the list since the start, including the United States, Canada and Mexico. But the list changes week to week. Switzerland, Jamaica and the Czech Republic are the latest additions, flagged Saturday. Portugal was on the quarantine list, then off and now might be headed back on. Greece may be next, after Scotland and Wales introduced their own measures for travelers returning from there.

That would mean a further economic blow to tourism-dependent Greece. Tourism Minister Harry Theoharis countered that coronavirus cases in his country are declining and below the British government’s quarantine threshold rate of 20 cases per 100,000 people over seven days.

The European Union has exempted British nationals from its coordinated travel restrictions, but individual countries within Europe have threatened retaliatory quarantines.

The travel industry says British is using a hammer when it needs a scalpel.

Willie Walsh, chief executive of International Airlines Group, which owns British Airways, lamented in the Times of London that the British economy “is being destroyed by the government’s blanket quarantine on travel from a staggering 160 countries. The UK has officially hung up the ‘Closed’ sign.”

But what the government is messaging in official communications is more resolute than what its monitoring effort signals.

“There doesn’t seem to be much enforcement,” said Gary McLean, an immunologist at London Metropolitan University. “It’s relying on people’s honesty, and I think that’s where it’s going to fall apart.”

A better system, he said, would be to test everyone who enters the country. “I know it’s a huge logistical exercise, but if you want to protect the border and stop importing cases, that’s simply what you have to do.”

Many travelers subject to the quarantine rules were surprised to find that their phones never rang.

Sean Callaghan, 60, a copywriter from Manchester, contrasted his family’s experience during a trip to a remote village in Spain with what happened when they returned to Britain.

On the ferry out, Spanish officials checked their temperatures and collected information on their intended whereabouts and how to contact them. There were no such checks on the return trip. British border officials merely asked to see passports.

His family, including two teenagers, spent the next two weeks self-isolating — and didn’t hear a peep from authorities.

“It’s just lip service. It’s a complete and utter joke,” he said. “You think that even one of us would have been contacted.”

He added that the British government “is flexing its muscles, saying, ‘We’re going to do this.’ But there is no policing of it behind the scenes.”

Transport Secretary Grant Shapps said that when his wife returned from Spain, she received a “random” call from officials to check that she was quarantining.

“They absolutely were checking,” Shapps told the BBC.

Wilder-Smith, the professor of emerging infectious diseases, said it would be more accurate to say Britain is pursuing a compromise strategy, assuming that many but not all will follow the rules — a policy that is less intrusive and less expensive than alternatives, and works as long as the number of new infections in the country do not soar.

“It’s not an unreasonable approach,” she said. “For now.”