The relatively low number of COVID-19 cases in Japan is likely due to limited testing.

Despite having cases detected earlier than most countries worldwide, Japan has seemingly not been overrun by the coronavirus.

This may lead to a “false sense of security” that could cause the virus to spread more rapidly than it has so far in Japan.

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As of Thursday, Japan has 924 cases and 29 deaths from COVID-19. With over 81,000 cases in China and over 8,500 cases in South Korea, experts wonder if Japan has kept the virus contained or just hasn’t tested enough of its population.

“The Japan conundrum is just the fact that if you don’t test for it, you’re not going to find a lot of cases,” says Jason Kindrachuk, PhD, an assistant professor of viral pathogenesis at the University of Manitoba.

Kindrachuk isn’t the only one who suspects underreporting. Kenji Shibuya, former chief of health policy at the World Health Organization, told Bloomberg that Japan has either “contained the spread by focusing on outbreak clusters, or … there are outbreaks yet to be found.”

With a population of over 126 million, the country has conducted 32,125 tests over the past month. However, because some people are tested multiple times, Japan has actually only tested 16,484 individuals – or about one test per 7,600 people.

In comparison, South Korea, with a population of over 50 million, seemingly slowed the spread of the virus by testing more than 270,000 people – one test per 185 people – through a well-organized program.

Earlier this week, Reuters reported that Japan is using one-sixth of its total testing capacity. The capacity for testing nationwide is 7,500 a day, but the health ministry says they do not need to exploit it now

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Japan was one of the first countries outside China to report a case of COVID-19, with its first case on January 16. The number of cases quickly escalated after the outbreak on the Diamond Princess cruise ship in early February. But since then, Japan’s cases have risen less rapidly than in other countries.

Japan took measures to prevent the coronavirus from spreading across the country last month. On February 1, it imposed a ban on any visitors from China’s Hubei province. On February 13, it added Zhejiang province to the restricted list. The country has closed schools and staggered commute times at rush hour to decrease crowds, although the current scene around Tokyo is still one of packed trains and restaurants.

Some experts have argued that the slow spread of the virus could be that Japanese culture is inherently more socially isolated than other cultures. Moreover, people in Japan have been wearing face masks when ill or have allergies for years, so this natural tendency may have also prevented the spread early on.

Kindrachuk doesn’t think this is the case but acknowledges it’s hard to say for sure. “There’s a lot of nuances to this virus that makes it exceedingly difficult to understand and ultimately contain.”

Currently, low case numbers may cause a “false sense of security” he says. There is the possibility the coronavirus has not spread to the most vulnerable populations yet – in other words, the low number of infected people in this group won’t necessarily stay that way.

“If you don’t actually test and know-how broadly distributed this virus is, the healthcare system can eventually be overrun, and then you’re back at square one.”