TOKYO — As the world tries to get a handle on the coronavirus and emerge from paralyzing lockdowns, public health officials have repeated a mantra: “test, test, test.”

But Japan went its own way, limiting tests to only the most severe cases as other countries raced to screen as many people as possible. Medical experts worried that the approach would blind the country to the spread of infection, allowing cases to explode and swamping hospitals.

It hasn’t happened. Japan — the grayest country in the world and a popular tourist destination with large, crowded cities — has one of the lowest mortality rates from Covid-19 among major nations. The medical system has not been overwhelmed. And the government never forced businesses to close, although many chose to.

This week, Prime Minister Shinzo Abe declared Japan’s battle against the outbreak a resounding success, taking the country off an emergency footing — a sort of “lockdown lite” that lasted only a month and a half.

“By doing things in a uniquely Japanese way, we were able to almost completely end this wave of infection,” Mr. Abe said, adding that what he called the “Japan model” offered a path out of the global pandemic.

It’s still unclear, though, exactly what accounts for Japan’s achievement and whether other countries can take lessons from its approach. Critics say Japan undercounted coronavirus deaths. And some warn that further waves of infection could undermine the government’s self-congratulatory pronouncements.

Instead of testing widely to understand and limit the virus’s spread through the general population, Japan has focused on quickly containing small outbreaks through contact tracing. Instead of dictating strict constraints on daily life, it has focused on educating people about measures like social distancing and gently prodding them to follow along.

Theories for the country’s relatively low mortality rate run the gamut from cultural attributes — widespread mask wearing, a practice of regular hand washing, a near absence of physical greetings like hugs and handshakes — to just plain luck.

A combination of many other factors, including government measures and changes in behavior among a public that feels strong pressure to follow the rules, could also be at work.

Individual actions “may seem small or mundane,” said Keiji Fukuda, an epidemiologist who directs the School of Public Health at the University of Hong Kong. But, he added, “the cumulative impact of all of those efforts across the entire country to really implement some kind of distancing” may have been substantial.

Whatever the formula, Japan has so far succeeded in keeping deaths low. The country has recorded fewer than 900 deaths even as the United States and European countries have reported tens of thousands.

Epidemiologists say widespread testing for the virus is important because it allows officials to isolate those who test positive, and to track trends in infection rates to help determine when it is safe to reopen schools, businesses and other places where people congregate.

Researchers at Harvard have said the goal should be to test nearly everyone who has at least mild flulike symptoms, as well as an average of 10 contacts for each person who tests positive.

Countries like South Korea and China that faced fast-growing outbreaks early in the pandemic quickly ramped up testing. China performed more than three times as many tests in Wuhan in a single day than those Japan has conducted nationwide since Feb. 18 — about 455,000 tests on around 278,000 people.

Japan initially told people who suspected they were infected with the virus not to seek help unless they had experienced a fever for four days, or two days if they were over 65. Even some people with seemingly severe symptoms were refused, provoking theories that the government was trying to hide the true extent of the problem.

Medical experts said the guideline was intended to conserve hospital resources. A national law on infectious diseases mandated that anyone who tested positive, even those who were asymptomatic, had to be placed in one of the country’s few isolation wards, creating a strong disincentive for doctors to test patients with milder symptoms.

The Japanese government also said early on that test kits must be rationed because they were in short supply. That argument has since faded, however, as Japan has never used even half of its testing capacity on any given day, and it has increased its testing capacity to just over 24,000 a day.

Japan has since eased its rules to allow those who test positive but are asymptomatic to stay in hotels. It is preparing to begin limited testing for antibodies, hoping to get a better grasp of the number of people who have been infected. It also plans to introduce a smartphone app to help with contact tracing.

Despite the constrained testing for the virus, the rate of positive results has dropped below 1 percent, a fact that the government’s expert panel on the virus says demonstrates that current testing levels are sufficient.

But a group of prominent Japanese academics, businesspeople and other figures has called on the government to take a much bolder step: build a capacity of 10 million tests a day and offer testing to anyone who wants it. Consecutive negative results, the group argues, could allow people to fully resume social and economic activities.

As the country has seemingly defied the odds, many public health experts, including some in the government, have warned against drawing any definite conclusions from Japan’s experience.

They caution that Japan is not in the clear yet, and that a second or third wave of infections could strike at any time. As more data on deaths from this year becomes available — there are indications that Tokyo has undercounted dozens of coronavirus deaths — the picture may not look quite as good.

Some say Japan may have a large hidden population of asymptomatic cases. Shigeru Omi, the deputy head of the government’s expert panel on the coronavirus, told lawmakers that the real number of infections could be as much as 10 or 20 times as high as currently believed. Japan has reported fewer than 17,000 cases, versus more than 1.7 million in the United States.

Norio Sugaya, an infectious diseases expert at Keiyu Hospital in Yokohama, noted that Japan’s mortality rate, while vastly lower than those in hard-hit countries like Spain or Britain, is one of the worst in Asia.

In February, an outbreak of the virus aboard the cruise ship Diamond Princess left officials scrambling. The response was widely seen as a disaster, but health experts turned it into a learning opportunity.

Epidemiologists and public health experts used the data from the ship to help develop a framework for stopping the virus’s spread in Japan.

The approach emphasized reducing people’s exposure to the conditions that led the pathogen to spread on the ship. A public education campaign urged people to avoid the “Three C’s” — closed spaces with poor ventilation, crowded places and close contact.

On TV talk shows, hosts took a “no question is too stupid” approach to talking about the virus, assuaging viewers’ anxiety and stressing the basic science of prevention: wash your hands, wear a mask, keep your distance from others.

At the same time, community health centers raced to investigate clusters using a monitoring system that had been developed to trace cases of influenza and tuberculosis.

Another key factor may have been Mr. Abe’s decision to close schools in late February, well before almost any other country. The decision was hugely unpopular, but it appears to have provoked an almost instantaneous change in behavior, according to polling conducted by researchers at Hiroshima University.

The day after the announcement, the percentage of people who were avoiding crowded places nearly doubled, rising to almost 60 percent. By mid-March, it was over 75, the study found.

In April, as cases began to spike, Mr. Abe declared a state of emergency. Businesses were requested to close or reduce their hours. People were asked to make only necessary trips. There were no penalties, but many complied anyway.

Makoto Sasho, 50, decided to close his grilled eel restaurant in the Meguro neighborhood of Tokyo and focus on delivery and carryout, despite assurances from the government that businesses like his could continue table service.

“We conformed to society’s expectations of us,” he said, adding that “when I thought about the future, I knew we absolutely could not be responsible for a cluster.”

As Japan now begins to reopen, some experts fear that people will begin to let down their guard.

In a speech on Monday night, Mr. Abe emphasized that the end of the state of emergency did not mean a return to normal life.

“What we need to aim for,” he said, “is establishing a new normal.”

Mr. Sasho said that his customers were clamoring for him to reopen, but that he was not sure he was ready.

“It’s a new way of life,” he said. “Maybe I’ll just stick with delivery and takeout.”

Motoko Rich contributed reporting.