The entertainment venues in Korea’s capital Seoul had just opened when they were forced to shut down after 17 new coronavirus cases were linked to a single man who has visited three nightclubs on May 7.

In only a few days, health officials have tested 65,000 people connected to these events and they believe the situation is now under control — a textbook example of how to deal with an infection cluster.

Over the course of the pandemic, South Korea has been widely hailed as a model in dealing with the outbreak. While the country’s approach to personal privacy is controversial, you can’t really argue with their results.

Although they were one of the first countries to suffer an outbreak and although the country went to a few thousand cases very fast, they still managed to control it using a mixture of widespread testing, quarantine, and contact tracing.

No room for complacency

For weeks on end, South Korea managed to keep its number of new infections in check, with only ~10 new cases every day.

As the country nervously started relaxing its quarantine, things went fine — until bars and clubs were reopened. Just one day after that, the Korean authorities reported 18 new infections, and the next day, 34 more. That might not seem much for countries dealing with thousands of new infections every day but for South Korea, it was a clear alert that the epidemic is far from over.

“Now’s not the time to let our guards down,” said Yoon Tae-ho, a high-level official from the Korean central government’s Covid-19 command center. “A ‘silent transmission’ that we don’t know about could exist.”

Indeed, the Korean government did not settle for complacency. In a matter of days, they tested 65,000 people who went to clubs or bars in the Itaewon neighborhood in Seoul — as well as those who were in contact with these people. In total, the authorities found 170 infected people who have been traced to the clubbing cluster — 89 clubgoers and 81 of their friends and relatives.

Lessons for other places

Now, the cluster is under control, Korean officials say, but it goes to show just how easily things can slip out of control. The spread of COVID-19 has been repeatedly linked to superspreaders, and a single infected person attending an event can trigger a chain of infection.

The lesson is valid for Korea as well as other countries: even if you do everything right, even if you all but eliminate the disease, it doesn’t guarantee that things will go smoothly. All countries and states must be prepared to act quickly and nip any infection cluster in the bud.

Similar clusters have been reported in other countries of Asia where the disease had been previously kept under control. Without rapid intervention, these clusters can easily turn into full blown hotspots. It’s something that areas relaxing the lockdown need to consider carefully.