In mid-August, Japan was recording over 20,000 daily coronavirus cases, its highest levels during the pandemic. On Wednesday, it reported just 310 nationwide.About 70 percent of the eligible population has been fully vaccinated, the government announced Wednesday, and life in the country has returned to a state of cautious optimism and near normalcy from one of acute concern. Tokyo has lifted nearly all restrictions on daily life, and the subways, streets and shopping arcades are once again filled with people. The city has reported fewer than 50 daily cases for over a week.Experts in Japan are unclear about what caused the precipitous drop in cases, although they agree that high vaccination levels and ubiquitous masking are probably the most important factors keeping the virus at bay.In remarks to reporters on Wednesday, government experts said other factors, such as cooler weather, an effective testing regime and heightened caution during the recent surge in cases, may have also contributed to the sudden drop in cases.They noted that asymptomatic cases of the virus also seemed to be on the wane.Testing levels in the country, however, are significantly lower than in its peer countries, which could mean an underreporting of cases. At the peak, Japan was performing only around 270,000 tests a day.Unlike other countries, Japan had never gone into lockdown or put compulsory restrictions on people’s behavior. Instead, the government placed the country under a succession of national emergencies in which the authorities called businesses to voluntarily shorten their hours and urged citizens to reduce the amount of time they spent outside.Nevertheless, infection levels in the country have remained relatively low through the pandemic, peaking at around 23,000 in late August before rapidly dropping. Total deaths in Japan stand at just over 18,200.Despite the current low infection levels, government experts warn that the country could experience a new surge in cases in the winter as more activities move indoors. In preparation, officials say they will ease access to testing and increase the number of hospital beds available for coronavirus patients.Hisako Ueno contributed reporting.