Japan’s Covid case numbers have plummeted to the lowest in nearly a year while other parts of Asia are struggling with surging infections, Reuters reports, leaving health experts perplexed and raising concern of a winter rebound.
New daily cases in Tokyo dropped to 87 on Monday, the lowest number since early November last year and a huge decline from more than 5,000 a day in August when hospitals came under huge pressure.
The pattern is the same across the country. After a slow start, Japan has made rapid progress in its vaccination campaign, and almost six months of emergency distancing restrictions are likely to have helped stem the spread of the virus.
Nevertheless, the speed with which a wave of infections and hospitalisations fuelled by the infectious Delta variant has ebbed away has confounded the experts.
Kyoto University’s Hiroshi Nishiura is among those who believe the summer spike in cases was mainly due to trends in human activity.
“During the holidays we meet persons whom 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.
Recent record cases in South Korea and Singapore may be connected to some mid-year holidays, and a convergence of Asian and western holidays at the end of the year could lead to a “nightmare”, he said.
But other experts say infection trends have less to do with travel and more to do with regular, seasonal trends.
Jason Tetro, a Canada-based infectious disease expert and author of The Germ Code, said different age cohorts become “fuel” for the virus to perpetuate, depending on vaccination rates and prior infections, at different times.
“Without elimination of the virus, we will continue to see spikes until 85% of the population is immune to the dominant strain,” he said.
A theory gaining ground is that Covid and its variants tend to move in two-month cycles, though Tetro said the cycle is “more a factor of human nature than mother nature”.
Kenji Shibuya, a former director of the Institute for Population Health at King’s College, London, said he doubted that “the people’s flow” was driving the virus, as many government experts assert.
“It is primarily driven by seasonality, followed by vaccination and perhaps some viral characteristics which we do not know,” said Shibuya, who also directed municipal inoculations in northern Japan.
Whatever the cause of the lull, experts say time is of the essence to head off another resurgence.
“We only have a window of one month,” Shibuya said. “So we should move fast to secure beds and ramp up vaccination.”