Covid 19 coronavirus: Japan defies health expert fears and avoid massive coronavirus, while experts query the mystery of why

Japan has defied fears it could become the next coronavirus hotspot like the United States or Italy and is now being touted as a success story, even if experts aren't exactly sure how it's so far managed to avoid a worse outbreak.

The country's dense, ageing population is a recipe for disaster when combating a virus that spreads in close contact and is particularly deadly for older people.

On top of this, the country had a massive outbreak aboard a cruise ship, and there were concerns it wasn't testing enough people — with some speculation this was a strategy to preserve the now postponed Tokyo Olympics.

This isn't to say it's been unaffected: the country has confirmed 16,513 infections and 796 people have died, but against its population of more than 126 million it's doing remarkably well.

Even here in Australia, where restrictions are beginning to ease and people are at least seeing light at the end of what remains a very long tunnel, more than twice as many people have been infected as a proportion of total population.

It's possible actual case numbers could be higher in Japan given the low number of tests being carried out.

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Japan's state of emergency over the Covid-19 pandemic ended earlier this month. Photo / AP

Japan opted for a more conservative approach to testing in a bid to avoid test centres being overloaded with people wanting to be tested, potentially creating a new cluster where people can be infected.

Instead the country only tested people displaying symptoms, which Australia initially did as well before expanding testing in a bid to find more cases, even though that would inflate the figures.

Currently one in approximately every 7630 people in Japan have been confirmed infected, compared to one in every 3515 Australians.

Japan has had a higher proportion of deaths, likely due to the ageing population that sparked some of the initial fears.

In Tokyo, where more than 14 million people live in an area smaller than Adelaide, new infections have remained below 40 a day for more than a fortnight, often under 10 new cases.

On Friday Tokyo reported just three new cases.

So what did Japan do differently?

Well for starters, and somewhat surprisingly, it appears the numbers haven't been kept down by the wide-ranging, some say overbearing, restrictions imposed in other countries.

Japan's version of a state of emergency involved asking people to stay home rather than telling them, restaurants were still allowed to open with slight restrictions, but there were no penalties for ignoring the requests.

Japan's Prime Minister Shinzo Abe. Photo / AP

So far there's no "silver bullet" to learn from Japan, health experts are still somewhat mystified about the country's seeming success.

But that hasn't stopped them sharing theories.

Nobel prize winning immunologist at Kyoto University Tasuku Honjo told ABC News it could be a confluence of factors that relate more to Japan's people and culture than any pandemic intervention.

"People in this country are generally very clean. They like to be clean, they wash hands very frequently on normal days and they don't kiss, they don't hug," Honjo said.

He also mentioned a circulating theory that a tuberculosis vaccine given to Japanese children could have boosted immunity.

Japan also has universal healthcare, as does Australia, the UK, and pretty much every other developed country in some form or another, the notable exception being the United States, where more people have been infected and died than anywhere else.

Japan's population also has an extremely low rate of obesity, which has also been highlighted as a likely factor in the severity of disease in coronavirus infected patients.

But Honjo warned the country hasn't fully beaten the virus just yet.

"We may expect another wave," he warned, "but so far this is still a mystery to most of the medical scientists".

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