It began with clubhopping.
South Korea reported its highest number of new coronavirus infections in weeks on Wednesday.
Forty newly confirmed cases — the biggest daily jump in nearly 50 days —raised alarm as millions of children were returning to school.
All but four of the new cases were in the densely populated Seoul region, where officials are scrambling to stop transmissions linked to nightclubs, karaoke rooms and an e-commerce warehouse.
The outbreak linked to nightclubs in Seoul has tested South Korea’s widely praised method for dealing with the disease , essentially a combination of rapid tracing, testing and treatment, along with stringent social distancing practices.
The first confirmed patient in the new coronavirus cluster was a 29-year-old man who visited five nightclubs and bars in Seoul's Itaewon entertainment neighborhood in a single night before testing positive for the virus. Further investigation has since found more than 100 infections that appear linked to the nightspots.
South Korea has reported 269 deaths and 11,265 cases, after managing to contain a severe earlier outbreak.
Authorities were testing 3,600 employees of a local e-commerce giant, Coupang, after discovering dozens of coronavirus infections linked to workers at the company's warehouse near Seoul.