The latest cluster of novel coronavirus infections blamed on clubs in Seoul’s popular nightlife district of Itaewon looks serious.

The accumulated number of confirmed cases related to Itaewon clubs marked 86 as of noon on Monday. It was only five days since a 29-year-old man residing in Yongin, Gyeonggi Province, tested positive for the virus on May 6, five days after visiting five clubs in Itaewon on the night of May 1. About 30 percent of infections related to the clubs are asymptomatic. This incident should wake people up to the rapidity of the virus spread.

Korea has been praised by foreign news media for handling its COVID-19 epidemic relatively well, but now it faces a tough challenge again.

The situation is not easy. Infections linked to the clubs show a trend of spreading nationwide. Confirmed cases were found among visitors who reside in Gyeonggi, North Chungcheong and North Jeolla provinces and Jeju Island, as well as the metropolises of Seoul, Incheon and Busan.

More concerning are secondary infections. Club visitors are spreading the virus to family members, fellow workers and friends.

The cluster of infections from the clubs was triggered by a patient carrying the virus in a state of incubation and showing no symptoms. It evokes the nightmarish COVID-19 surge in Daegu among members of the Shincheonji religious sect.

The Itaewon clubs in question are located in central Seoul and frequented by foreigners as well as Koreans. Under social distancing guidelines, the clubs made a list of visitors at the entrance, but not all of the names and contact numbers were correct. Some gave false information.

For the long holiday period from April 30 to May 5, a total of 5,517 people were found to have visited the five Itaewon clubs. Of them, 3,112 were reportedly out of contact.

Among COVID-19 cases related to the clubs are workers at a clinic, a department store and a call center. These are places vulnerable to cluster infections.

Several visitors to the clubs tested positive along with the Yongin patient on the same day. Infections might have already proceeded in different places simultaneously before their visit to the clubs.

The government eased high-level social distancing on April 20. It lowered the level of advice from “business suspension” to “business restraint” for entertainment establishments such as clubs and bars, as well as religious, indoor sports and private tutoring facilities.

At that time, quarantine authorities were concerned about clubs crowded on weekends. It is questionable if the government had to ease restrictions on high-risk facilities not essential to everyday life. It should have been more prudent.

Furthermore, it is not realistic to expect clubs and visitors to comply with administrative orders to keep masks on and maintain 1 to 2 meters of distance from one another inside the clubs. The government needs to review its quarantine measures.

Massive infections can happen not only in clubs and bars but in any crowded establishment. Even after Seoul banned the operation of clubs and hostess bars for two weeks from May 9, pubs in the Gangnam and Hongdae areas popular with the young are said to be crowded with customers.

A large bushfire starts with small embers. When the people lower their guard, Korea will fall from a success model to a failed state. Vigilance is key to preventing another surge of outbreaks. Particularly young people must keep in mind that an individual’s aberration can undo many health care workers’ efforts so far to fight the disease.

It is urgent to trace all of the contacts and quarantine them quickly. Those who visited the clubs or who might have contacted the visitors should refrain from going outdoors, report to health authorities and undergo testing procedures if needed.

Laxity is what epidemiologists have warned of at all times. People must look back to see if they are too easygoing after the nation shifted to a mode of everyday quarantine. They must make a habit of abiding by disinfection protocols to prevent the spread of infections.