Japan rides calmer Covid-19 wave but new variant, resurgence of virus in Europe cause jitters

Japan's low Covid-19 count in recent weeks - compared to the resurgence of cases in Europe and parts of Asia - has baffled its experts. On Tuesday, the day before Tokyo reported its five new cases, there were only 107 cases reported across the nation of 125 million.

Those figures are in stark contrast to the 25,992 reported on August 20, the peak of the fifth wave of the pandemic to hit Japan, and a seven-day average of 21,247.

Asked about the reasons for the steep dive, Kazuhiro Tateda, president of the Japan Association of Infectious Diseases and a member of the government's advisory panel said: "We don't know for sure."

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"Right now, the most likely explanation is that it is a combination of several factors, to greater or lesser degrees," he said.

The high vaccination rate - after a lacklustre start - is a significant factor, Tateda said, with more than 196 million doses administered and nearly 78 per cent of the population double jabbed.

This cannot be the sole factor, however, as nearly 79 per cent of South Koreans are also fully vaccinated, yet the virus is once again raging there, he added.

"It is possible that another factor in the low rates at present is that so many vaccines were administered between July and September - 40 per cent of all inoculations in Japan were at this time - and we may be enjoying a higher level of immunity now," he said.

In contrast, South Korea and other countries began rolling out vaccines earlier and more gradually, meaning that efficacy may now be wearing off for those who had the jab early in the pandemic.

That is a cause for concern in Japan, Tateda added, as the around six-month effectiveness of the vaccine will be wearing off in the early months of next year. The European Union has proposed a nine-month limit on vaccine validity for travel.

"I fear that might be a dangerous time for Japan and we must keep our guard up," he said.

What experts are calling the "media effect" may be another reason why rates are presently so low, with extensive coverage of the health crisis encouraging people to remain careful when they have to go out and many people still curtailing visits to bars and restaurants.

"If you look around, virtually everyone is still taking the basic precautions against the virus, they are wearing a mask, using hand disinfectants, keeping their distance and so on," he said.

"That is perhaps an element of the Japanese character and culture, but it is proving beneficial in this situation."

Critics of the government's handling of the crisis though say the low numbers are due to poor testing rates. Japan's testing rates have remained consistently low among developed nations. Statistics from Our World in Data showed that on October 27, its seven day rolling average of tests performed per 1,000 people was 0.35, compared to 12.37 for Britain, 4.13 for Singapore and 2.22 for Canada.

The other reason for the low Covid-19 numbers was that patients have not been properly tracked, critics said. Those who tested positive have been encouraged to isolate at home to prevent the health care system from being overburdened. Hundreds of people isolating at home have since died of the virus, with one report suggesting that 250 patients died in August alone.

Nevertheless, deaths attributed to the disease have fallen in tandem with new infection numbers, with one fatality on November 24, down significantly from the 89 deaths reported as recently as September 8. In total, 18,344 people in Japan have died of the virus to date.

Health authorities have not always been able to keep accurate tallies of infection numbers, with the Tokyo Metropolitan Government confirming in late October that 4,512 cases of the virus were mistakenly left off reports in the six months from April 2 this year, while an additional 447 cases were reported twice.

A theory that has been mooted by Ituro Inoue, a genetics professor at the National Institute of Genetics, is that the highly infectious Delta strain of the virus effectively eradicated all other variants in Japan before mutating itself into extinction.

Covid-19 has a very rapid mutation rate, as do all viruses that have RNA or ribonucleic acid as their genetic material. This increases the likelihood of what scientists term an "error catastrophe," when bad mutations in the virus combine and, ultimately, make it unable to replicate. In Japan, the fault appears to be linked to the nsp14 protein, although Inoue and his team cannot say quite why or how it occurred in this population.

Inoue presented his findings to the government's panel earlier this month and Tateda said the theory is certainly plausible, although questions remain.

"One question is why this did not happen earlier as the error was already visible during the third wave of the virus, in January of this year," he said. "Also, this error has also been reported in a number of other countries in Asia, including Korea, Thailand and Vietnam, but the impact has only been seen in Japan. Why? We don't know."

Yoko Tsukamoto, a professor of infection control at the Health Sciences University of Hokkaido, agrees that the early vaccination programmes in other countries may be contributing to rising figures now, but also points to the link between latitude and infection rates.

"Every country has its own unique issues that impact infection rates, but there are new studies that link infection rates with latitude," she said. "Rates in Belgium and New York City are bad at the moment, and those two locations are on a similar latitude and have comparable population densities."

The theory holds that as temperatures fall with the arrival of winter, infection rates will increase. And that bodes ill for Hokkaido, Tsukamoto admitted.

"The situation here is not so good at the moment and rates are higher than other parts of Japan, and that seems to track with falling temperatures," she said. "These sorts of viruses seem to like temperatures of around 5 degrees to 15 degrees, while a lack of ultraviolet light may also have an effect."

If the theory is correct, then Japan may be on course for a bad winter, with meteorological experts warning of lower temperatures than usual this year and higher snowfall.

"I fear that in a few weeks, as temperatures in other parts of Japan begin to go down, that infection numbers may begin to rise again, despite vaccination numbers and all the other precautions that people are taking," she said.

The experts concur that Japan is not out of the woods yet, especially with the discovery of a new Covid-19 variant first discovered in South Africa.

"I think it's very likely that we are going to see another increase in the coming months, but I do think we are better prepared now," said Tateda. "The government has taken steps to have more beds ready at hospitals for when a new wave happens and pharmaceutical firms are close to developing an oral medicine.

"We have learned a lot and I think we can prevent a spike on the same scale in the sixth wave."

This article originally appeared on the South China Morning Post (SCMP).

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