It all began with an academy teacher from Incheon, who contracted COVID-19 from a nightclub in Itaewon.
From there, the virus has traveled from person to person all the way to a one-year-old baby.
Connecting the two cases were several degrees of transmission mostly centered around a singing booth that has become the city's ground zero.
One student who caught the virus from his academy teacher visited the singing booth, after which a series of other customers were infected.
"All the prevention measures - masks, 2 meter distancing, ventilation - are to block droplet transmissions. But none of that is possible in a singing room: you can't sing with a mask on, and you are in a small space with other people for a long period of time."
One of the singing room's customers then came in contact with the one-year-old baby.
And a man who visited a PC cafe in the same building also tested positive for COVID-19.
"Experts suggest elevators could be a possible source of transmission within buildings.
They say despite the anti-virus film, the virus can still live up to 4 hours."
Taxis and private academies are also at the center of the spread due to their enclosed environment.
And in such cases, it only takes a brief moment of contact for transmission to occur, as proven by CCTV footage of two students who had a single minute of contact in a classroom.
To cut this long chain of infections, social distancing is critical.
"Let's say, to stop a secondary infection from developing into a third degree transmission, you have to quarantine everyone who has had contact with patients in that particular stage, so they can't pass it onto others. The most effective way to do that is by voluntary distancing."
Self-hygiene such as wearing a mask and washing hands regularly can also help break the chain.
Lee Kyung-eun, Arirang News.