The mystery of Japan’s low coronavirus death rate

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Daily US Times: Japan’s low coronavirus death rate became a mystery that has spawned dozens of theories, from claims that the Japanese have superior immunity to Japanese manners.

Japan does not have the lowest death rate for Covid-19 – in the region, Hong Kong, South Korea, Taiwan, and Vietnam can all boast lower morbidity.

But Japan saw fewer deaths than average in the early part of 2020. This is despite the fact that in April, Tokyo saw about 1,000 “excess deaths’ – due to Covid- 19 perhaps. Yet, for the year as a whole, it is possible that overall deaths will be down on 2019.

This is particularly striking because the country has many of the conditions that make it vulnerable to Covid-19, but it never adopted the aggressive approach to tackling the virus that some of its neighbours did.

What happened in Japan?

At the height of the coronavirus outbreak in Wuhan in February, the world put up walls to Chinese travellers but Japan kept borders open. As the virus spread, it quickly became clear that it is a disease that primarily kills the elderly and is massively amplified by crowds or prolonged close contact.

Japan has more elderly people per capita than any other country. Its population is also densely packed into huge cities.

Greater Tokyo has a mind-boggling 37 million people and for most of them, the only way to get around is on the city’s notoriously packed trains.

Then there is Japan’s refusal to follow the advice of the World Health Organization (WHO) to “test, test, test”. Even now, total PCR tests stand at just 348,000, or 0.27% of the country’s population.

Japan had never imposed a lockdown on the scale or severity of Europe. The government ordered a state of emergency in early April. But the stay-at-home request was not mandatory, rather it was voluntary. Non-essential businesses were asked to close, but there was no legal penalty for refusing.

Many paragons of Covid strategy, such as Vietnam and New Zealand used tough measures including tight lockdowns, closing borders, large-scale testing and strict quarantines – but Japan did none of that.

Yet, five months after the first Covid case was reported here, Japan has fewer than 1,000 deaths and fewer than 20,000 confirmed cases.

Growing scientific evidence shows that Japan really has contained the spread of the disease – so far.

Prime Minister Shinzo Abe spoke proudly of the “Japan Model” as he announced the lifting of the state of emergency late last month, intimating that other countries should learn from Japan.

What is special about Japan’s low coronavirus death rate?

According to the Deputy Prime Minister Taro Aso, it is down to the “superior quality” of Japanese people. In a now notorious comment,the Deputy Prime Minister said he had been asked by leaders of other countries to explain Japan’s success.

“I told these people: ‘Between your country and our country, mindo (the level of people) is different.’ And that made them speechless and quiet.”

Mindo means “people’s level” if literally translated, although some have translated it as meaning “cultural level”.

It is a concept dating back to Japan’s imperial era and denotes a sense of cultural chauvinism and racial superiority. Mr Aso has been roundly condemned for using it.

But there is no doubt that many Japanese, and some scientists, think there is something behind Japan’s low coronavirus death rate, which is different – a so called “Factor X” that is protecting the population from Covid-19.

It is possibly relevant that some aspects of Japanese mores – few kisses on greeting and few hugs – have in-built social distancing, but nobody thinks that is the answer.

Does Japan have special immunity?

Tatsuhiko Kodama, a Tokyo University professor, who studies how Japanese patients react to the virus – believes Japan may have had Covid before. Not Covid-19, but something similar that could have left behind “historical immunity”.

”When a virus enters the human body, the immune system produces antibodies that attack the invading pathogen”, he explains.

There are two types of antibody – IGG and IGM. The way they respond can show whether someone has been exposed to the virus or something similar before.

The Professor told the BBC: “In a primary (novel) viral infection the IGM response usually comes first. Then the IGG response appears later. But in secondary cases (previous exposure) the lymphocyte already has memory, and so only the IGG response increases rapidly.”

So, what happened with his patients?

“When we looked at the tests we were astonished… in all patients the IGG response came quickly, and the IGM response was later and weak. It looked like they had been previously exposed to a very similar virus.”

He thinks it is possible a Sars-like virus has circulated in the region before, which may account for the low death rate, not just in Japan, but in much of China, Hong Kong, Taiwan, South Korea, and South East Asia.

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