“We believe we will have another community infection,” said Vice Health Minister Kim Gang-lip at a Friday press briefing. “The spread took place in enclosed and crowded spaces. Transmission with no known source of infection can lead to a widespread cluster infection and that is why the government is not letting its guard down.”

The man in question had no symptoms when he visited the nightspots. He eventually tested positive on Wednesday and gained admittance to a hospital in Suwon, a city south of Seoul, according to the UPI wire service.

Officials think he may have come in contact with over 1,500 people during his night out. City officials are now using CCTV and credit card records to help identify visitors and are encouraging them to self-isolate and immediately report any coronavirus symptoms to local hospitals.With a decline in new cases, South Korea has allowed places of worship, museums venues, recreational facilities and nightclubs to recently resume business. The country’s high schools begin reopening next week and its lower schools will gradually reopen throughout May.

However, similar to the reopening plans of many U.S. states, South Korea has said it will pull back on and reverse reopenings if new cases emerge.

While the number of coronavirus cases in South Korea originally exploded in late February and early March, the country’s Ministry of Health worked hard to conduct rigorous contact tracing, contacting anyone who had attended venues where patients with confirmed cases of coronavirus had gone. Using a combination of interviews and cellphone surveillance, anyone in proximity to these patients and their neighbors were widely tested and all encouraged to self-quarantine.