South Korea counted 12 additional cases of novel coronavirus infections in the 24 hours ending Wednesday midnight. Despite the slowing of new cases, symptomless or minimally symptomatic spread among the younger population remains a challenge for containment efforts, public health authorities said.

Korea Centers for Disease Control and Prevention’s Deputy Director Kwon Jun-wook said in a Thursday briefing that 10 out of 12 new cases were local cases, mostly linked to the early May outbreak in Itaewon, a nightlife district in Seoul.

Of the 201 virus patients with ties to Itaewon, 95 were visitors of the nightclubs and 111 were their contacts, he said.

“Virus transmission can occur in any settings where people gather and have contact,” the deputy director said, warning that “no one, not even young people, is immune from infection.”

“Social distancing, maintaining personal hygiene and cough etiquette remain our best defense against the virus,” he said.

Korea has tested 788,684 people so far to find that 11,122 were infected. Over 91 of the patients, or 10,135, have been released from care after recovering.

One death linked to the virus was reported Thursday, with the fatality rate standing at 2.1 percent. The death toll now totals 264.

Health Minister Park Neung-hoo said in a Central Disaster Management Headquarters meeting Thursday morning that the outbreak in Itaewon had “spread mainly through facilities where there had been a lack of safety precautions.”

To prevent future lapses, “a more coherent infection surveillance system” will be established, he said.

The minister stressed that because schools are back in session, students are strongly urged not to go to places where there is a high risk of infection, such as gaming cafes and any place where wearing face masks and keeping distance are not viable.

In Incheon, where a series of fresh infections forced 66 high schools to suspend classes yet again, all karaoke bars are ordered to close from Thursday, health officials said. The measure comes after two high school seniors there were found on Wednesday to have contracted the virus after visiting karaoke lounges.

“Given Incheon’s proximity to densely populated Seoul, delays in contact tracing can lead to large-scale transmissions,” said senior health official Yoon Tae-ho during a press briefing Thursday morning, urging people to get tested if they had been to places where infections had been detected.

Since the first case in the Itaewon cluster was discovered May 6, at least 248 visitors to nightspots in the area remained unreachable, he said.

Addressing the recent infections among health care workers at Samsung Medical Center in Seoul, the city’s health officials said they were testing over 1,400 people who may have been exposed. After a nurse tested positive on Monday, three more cases at the hospital have been confirmed.

Meanwhile, in the past 24 hours, the world saw the largest single-day increase in new cases of 106,000, according to the World Health Organization, which said the global total was nearing 5 million.

“We still have a long way to go in this pandemic,” said the chief of the United Nations agency, Tedros Adhanom Ghebreyesus, in a Thursday media briefing.

“But the good news is that it has been particularly impressive to see how countries like the Republic of Korea have built on their experience of MERS (Middle East respiratory syndrome) to quickly implement a comprehensive strategy to find, isolate and care for every case and trace every contact,” he said.

This approach, he added, was critical to Korea “curtailing the first wave and now quickly identifying and containing new outbreaks.”

By Kim Arin (arin@heraldcorp.com)