Covid 19 Delta outbreak: Japan baffles experts as cases suddenly plummet

Covid-19 cases in Japan have plummeted following the Olympic Games. Photo / Getty Images

If you cast your mind back to winter, when Covid began to cause fresh headaches, there was a saving grace for many of us who were locked in their homes with nothing to do: the Olympic Games in Tokyo.

Despite our enjoyment of the Olympics from afar, there was a debate around whether the games should have gone ahead, given what was happening in Japan at the time.

The nation of 125 million had done reasonably well for a country of its size and population density before then, keeping Covid cases relatively under control and preventing deaths from the virus.

But then, things started to head south in July with the introduction of the Delta strain.

It was terrible timing for Japan, with the Olympics about to bring athletes and dignitaries from all around the world into the country just as cases began to take-off.

Many residents and health experts wanted the games to be called off.

There were fears of cases spiralling out of control and mass deaths, and it appeared at first that those concerns were justified, as cases began to mount throughout the spectacle.

Exterior view of Ariake Urban Sports Park, a venue for cycling (BMX freestyle, BMX racing) and skateboarding at the Tokyo Olympic Games. Photo / Photosport

Things were not looking good after athletes returned home either, as infections kept rising.

By the end of August, Japan — which has the world's third largest economy — was clocking more than 24,000 cases a day. Deaths began to climb too, with the seven-day average hovering around 50-60 for several weeks.

However, something truly remarkable has happened since then, and experts around the world can't believe what they are seeing.

As cases rise in other parts of Asia, infections in Japan have plummeted to their lowest levels in nearly a year.

New daily cases in Tokyo dropped to just 87 on Monday, the city's lowest tally since November 2 last year and a massive decline from the thousands of new cases each day seen just a matter of weeks ago.

Other cities around the nation are seeing the same trend, with the average number of daily new infections falling by more than 8000 in the past three weeks.

Experts scratching their heads

The huge decline in cases is obviously welcome news to Japanese residents, but the reasons are perplexing experts around the world.

Professor Mark Woolhouse, epidemiologist at the University of Edinburgh, said the plunge was probably because the Delta variant appears to "move faster through populations".

"Spikes for the Delta variant tend to be spikier. They go up faster, and they come down faster," he told the UK's inews.

Although the drop in cases itself is not a "particular surprise", cases have come down "fast", he said.

"We first saw that in the first wave of Delta, which hit India and that had the same characteristic; it went up very fast, and it came down very fast," he said.

He added that the Delta variant has a shorter "generation time", meaning how long it takes one infected person to infect another.

He and government experts in Japan have put the drop in cases largely down to vaccinations and recent restrictions linked to the state of emergency.

Much of Japan has been under virus emergency measures for a large part of the year, with the restrictions finally lifting last week because of the decline in infections.

Other experts, like Kyoto University's Hiroshi Nishiura, say the recent spike in cases has ended because of changes in the flow of people, with fewer travellers now holidaying and socialising in Japan.

Nishiura believes infectivity, as measured by the effective reproduction number, is correlated with holiday breaks.

"During the holidays, we meet persons we seldom meet up with, and moreover, there is a substantial chance to eat together in a face-to-face environment," Nishiura, a top infectious disease modeller advising the government, told Reuters.

He said recent record cases in South Korea and Singapore may be connected to mid-year holidays, and a convergence of Asian and Western holidays at the end of the year could lead to a "nightmare".

Another school of thought is that the virus comes in vicious cycles, fuelled by one particular age demographic.

Jason Tetro, a Canada-based infectious disease expert and author of The Germ Code, said different age cohorts become "fuel" for the virus to spread, depending on vaccination rates and prior infections, at different times.

"Without elimination of the virus, we will continue to see spikes until 85 per cent of the population is immune to the dominant strain," he told Reuters.
"This is the only way to get out of these vicious cycles."

Another theory is that Covid-19 and its variants tend to move in two-month cycles, though Tetro argued the cycles were "more a factor of human nature than mother nature".

Fears as Japan heads into winter

Although cases have dropped significantly, there are fears of another wave as the nation heads into winter.

More than 60 per cent of the population is now fully vaccinated, but there are concerns that the healthcare system could easily become overwhelmed again, should a new wave emerge.

Japan's vaccination rollout was initially slow compared to other G7 nations. Frontline health care workers were jabbed on February 17, but the rollout to older people did not start until late April.

However, Japan picked up quickly and now more than 158 million doses have been administered, with 63.5 per cent of people aged 12 and over double jabbed. That's 57 per cent of the total population.