SEOUL - South Korea has reported a sudden spike of 20 new cases of coronavirus infection, raising concerns about a potential “super spreader” who has already infected 14 people in church.

This brings the total number of cases in the country to 51, sending alarm bells ringing as the government scrambled to strengthen quarantine measures to contain possible community spread.

Epidemiological investigations showed that 14 of the new cases revealed on Wednesday (Feb 19) attended the same church as the 31st patient - a 61-year-old Korean woman who developed sore throat on Feb 8 and was diagnosed on Tuesday.

It is not clear how she could have contracted the virus as she did not travel overseas recently and had no contact with the confirmed cases before her.

The woman, a native of the south-eastern city Daegu, is known to have come into contact with 166 people, all of whom have been quarantined. They include her husband and two children.

The Korea Centres for Disease Control and Prevention (KCDC) said the woman was warded for 10 days from Feb 7 at Saeronan Oriental Hospital in Daegu. She was hospitalised after a car accident on Feb 6.

As her injuries were minor, she left the hospital to attend a two-hour religious service at Shincheonji Church of Jesus on Feb 9, and again on Feb 16. She also had lunch with an acquaintance at a hotel buffet restaurant on Feb 15.

The cluster of 14 infections in the church includes men and women living in Daegu and the eastern Gyeongsangbuk province.

Shincheonji Church of Jesus was founded in 1984 by religious leader Lee Man-hee, who has been accused of heading a cult.

The KCDC said on Wednesday that they are planning to conduct tests for the entire church as a precaution, and that further investigation is needed to determine the source of infection and how it has spread.

The agency is also reviewing policies about how to deal with patients who refuse to be tested for the coronavirus, after it was revealed that Patient 31 had refused testing despite having a fever. The police could be called in to assist, they added.

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Patient 33, a 40-year-old woman, is also linked to Patient 31. They came into contact at Patient 33’s workplace - Saeronan Oriental Hospital.

Health authorities have warned of a potential community spread as experts attempt to trace how the new spate of cases could have spread. At least four people who tested positive for the virus have no links to previous infections or any travel history.

But the authorities also urged calm, saying that it is still too early to judge if the situation is a full-blown outbreak.

As of Wednesday, South Korea has tested 10,411 people for the virus, with 1,030 under quarantine. Sixteen people have been discharged after making full recoveries.