TOKYO >> By luck or by design, Japan has been spared a devastating outbreak of the coronavirus occurring in other parts of the world.

That the nation sidestepped disaster without knowing how is cause for both celebration and concern. What matters now, as the last of its prefectures have reopened, is whether the government’s strategy will keep working.

While reactive countermeasures and delayed contingencies seem to have pacified the contagion so far, a more secure strategy may be necessary to prevent a second wave in what is shaping up to be a long fight against the global pandemic.

“We need to build upon what we, as a society, have learned during this pandemic and use that knowledge to forge a new lifestyle,” said Koji Wada, a public health professor at the International University of Health and Welfare.

That lifestyle, he noted, will need to be maintained for one or two years, maybe even three, until a suitable treatment or vaccination for COVID-19 is created.

Japan seemed ripe for a major outbreak when the contagion reached its shores. And Tokyo, one of the most densely populated cities on the planet, resembled a petri dish. From the careless airport screening of Japanese citizens evacuated from Wuhan in January, to the questionable procedure of disembarking passengers from a virus-infested cruise ship in Yokohama Bay a month later, there were multiple opportunities for the virus to gain a foothold in Japan.

But a major outbreak hasn’t hit — yet.

Since the onset of the pandemic, the government has focused on testing individuals at high risk of infection. While other countries such as South Korea have tested as many people as possible, Japan has conducted targeted testing.

The low number of tests implemented has made it difficult for experts to get a grasp on the spread of the virus. This strategy, as well as the inability of municipal leaders to legally enforce citywide lockdowns, has drawn heavy criticism.

And yet, the coronavirus outbreak in Japan has been largely kept in check. So far, the country has reported more than 17,000 cases and about 850 deaths.

In comparison, the United States is facing huge challenges with more than 1.6 million cases and some 100,000 deaths. The United Kingdom, Spain, Italy and France have also suffered heavy casualties. Worldwide, the pandemic has infected more than 5.3 million people and taken the lives of more than 344,000 patients in at least 177 countries.

There are countless theories as to how, why and what conditions have allowed Japan to avoid calamity. The truth remains elusive.

Shigeru Omi, former director of the Western Pacific Regional Office of the World Health Organization, theorized that Japan avoided the disaster seen in Western countries due to three factors: its health care system, effective cluster tracing in the early stages of the epidemic and a propensity among its people for healthy living.

Last week, a task force was formed to figure out if the low number of severe cases in Japan was a matter of genetics. Others have postulated that the strain of coronavirus spreading in east Asian countries is less aggressive than the one wreaking havoc in Europe and the Americas.

Japan has been heavily criticized for conducting fewer tests than other countries. Rumors emerged that the government wanted to minimize the number of reported infections to prevent a postponement or cancellation of the Tokyo 2020 Olympic Games.

Experts say Japan’s death count is probably the most reliable indicator of the situation, since the figure would be difficult to hide or manipulate.

But because of the low testing numbers, Omi said the number of cases nationwide “could be 10 times, 15 times or even 20 times higher than what’s reported.”

Thus, the threat of a second wave looms large.

Prime Minister Shinzo Abe declared a state of emergency across seven prefectures April 7, extending it on April 16 to the rest of the country. The declaration was set to expire on May 7, but Abe extended it to May 31.

Then on May 14, the government lifted the order in 39 prefectures deemed safe enough to reopen. Last week, the order was lifted in Osaka, Kyoto and Hyogo prefectures. And on Monday, the state of emergency for the five remaining prefectures — Tokyo, Saitama, Chiba, Kanagawa and Hokkaido — was lifted as well.

While restrictions to slow the spread of the virus have been voluntary, according to data for April 4 to May 16 by Google LLC, nearly all sectors of Japanese society saw a drop in activity: businesses saw a 40% drop, workplaces a 23% drop and public transportation hubs a 55% drop.

Kenji Shibuya, a senior advisor at the WHO, said a second wave of the coronavirus in Japan is “inevitable.”

“It’s better to assume that there will be a second wave,” said Yasutoshi Nishimura, a cabinet minister charged with managing the virus. “Small waves are inevitable, and those will turn into a big wave if we let our guard down.”