Health authorities and municipalities are conducting an epidemiological study to trace, test and isolate those who have come into contact with the man.

“We identified about 57 contacts, but there is a very high possibility that the number will increase,” said Korea Centers for Disease Control and Prevention Deputy Director Kwon Jun-wook.

One of the contacts, a 31-year-old living in Anyang, Gyeonggi Province, who accompanied him on the trip to Itaewon, also tested positive, according to the Anyang City government.

Their night out in Itaewon on Friday involved visits to some two convenience stores, and five bars and nightclubs, according to the Yongsan-gu Office, which has jurisdiction over Itaewon. An estimated 2,000 people are believed to have come into contact with them.

The Yongin patient began to show symptoms -- high fever and diarrhea -- Saturday, visited a local clinic Sunday and was tested Tuesday, according to the initial epidemiological study.

According to the information on his movements released by municipalities, he went on trips to other cities in Gyeonggi Province and Gangwon Province. He also visited a restaurant, supermarket, clinic, shop and pharmacy during the recent six-day holiday that started April 30.

Including the Yongin resident, Korea reported four new COVID-19 cases Thursday, three of which were imported, according to the Korea Centers for Disease Control and Prevention. The total number of coronavirus cases here stands at 10,810. The Anyang resident’s case is not included in the past 24-hour tally released Thursday, but will be part of the next update, to be announced Friday.

The number of newly confirmed cases on a daily basis has stayed below 20 for 20 consecutive days, and under five since Tuesday, with nearly 78 percent of the new cases for the past two weeks coming from overseas.

The slowdown in infections led the government to ease its social distancing campaign starting from Wednesday, with museums, libraries and schools beginning to reopen. Strict restrictions on entertainment establishments were also lifted.

But health authorities are on alert over cases in which the source of infection remains unknown, and over the increased movement of people over the recent holiday. Some 6.5 percent of the new cases for the past two weeks were from unknown sources of infection.

The nation’s death toll increased by one to 256, with the overall fatality rate at 2.37 percent. The rate for patients aged 80 and older stood at 25 percent, according to KCDC data.

A total of 9,419 people have fully recovered from the virus, putting the recovery rate at 87.1 percent.

By Ock Hyun-ju (laeticia.ock@heraldcorp.com)