South Korea reported 79 new coronavirus cases on Thursday, the most in nearly eight weeks, triggering the return of tougher social distancing curbs amid the spectre of a second wave of disease in a country praised for containing the first outbreak.
At least 82 cases this week have been linked to a cluster of infections at a logistics facility run by Coupang Corp, one of the country's largest online shopping firms, in Bucheon, west of Seoul, the Korea Centers for Disease Control and Prevention (KCDC) said.
About 4,100 workers, including 603 delivery people, at the warehouse were believed to have not properly followed social distancing and protective measures, such as mask wearing, KCDC deputy director Kwon Jun-wook told a briefing.
Coupang, one of a group of e-commerce firms whose plants have scrambled to fill a surge in demand, has said the Bucheon centre was disinfected every day, with all employees wearing masks and gloves and their temperatures checked.
"We'll take every measure we can take until safety is confirmed," a Coupang spokeswoman said.
The new cases on a third straight day of rising infections took South Korea's tally to 11,344 with 269 deaths by midnight on Wednesday. A robust testing programme this year was credited with keeping deaths comparatively low in a global pandemic that has now killed more than 350,000.
The warehouse cluster appears linked to an outbreak that emerged in several Seoul nightclubs and bars in early May, the KCDC said, and comes amid efforts to ease social distancing rules. More than 2 million children returned to class on Wednesday, the latest in a phased opening of schools.
Unlike many countries, South Korea did not impose a strict lockdown against the virus.
But the rise prompted health officials to call on Thursday for a return to tougher social distancing rules in major metropolitan areas, including closing some public places, such as museums, and getting employers to adopt flexible work plans.
Health officials said they would perform on-site inspections of logistics centres nationwide, to develop better prevention policies.
Bucheon city officials announced a return to intensive social distancing, which means closure of places of worship, sport fixtures and other public facilities.
Coupang, backed by Japanese tech conglomerate SoftBank Group, said it closed the Bucheon facility on Monday. On Thursday it said it had also closed a facility in Goyang, in the Seoul suburbs, after an employee tested positive there.
"As soon as the employee's diagnosis was confirmed, Coupang sent home and self-quarantined employees who had contact with the employee," it said in a statement.
The spreading outbreak and warehouse closures come as orders rocket at e-commerce firms, with more people opting to shop from home, even without a strict lockdown.
In February, March and April, online retailers, including Coupang, saw sales jump 34 percent, 17 percent and again 17 percent respectively over the corresponding months a year earlier, trade ministry data shows.
That compared with offline retailers' sales, which dropped 7.5 percent, 18 percent and 5.5 percent in the same three months from a year earlier.