South Korean health authorities are racing against time to prevent a massive second wave of coronavirus infections, as contact tracing is fraught with challenges.

At the center of the problems is a church led by a far-right pastor and vocal critic of President Moon Jae-in, with followers from all over the country -- many of them participated in a massive anti-government rally Saturday.

An accumulated number of cases traced to the church stood at 457 as of Tuesday noon, up 138 from a day earlier, according to the Ministry of Health and Welfare.

Breach of virus protection rules coupled with an uncooperative response to antivirus measures by the pastor and members of Sarang Jeil Church in Seongbuk-gu appear to make it harder for health officials to control the situation than when dealing with previous mass infection clusters, as in Seoul’s popular nightlife district Itaewon and the Shincheonji Church of Jesus.

At least 10 members of Sarang Jeil Church attended at least one of two protests near the main palace Gyeongbokgung on Aug. 8 and at Gwanghwamun Plaza on Saturday.

The church’s Rev. Jun Kwang-hoon tested positive Monday after joining the weekend anti-government rally along with thousands of people, where they shouted slogans and sat close to one another.

Given that a large number of unidentifiable people gathered for the rallies, concerns are mounting over possible chain transmissions.

“We are very concerned over the possibility that additional infection spread could have been caused by close contact during rallies,” Vice Health Minister Kim Gang-lip said during a daily briefing Tuesday morning.

Kim urged those who joined the two rallies to get tested at nearby community health care centers regardless of symptoms.

While the church-linked infections centered on Seoul and surrounding areas like Gyeonggi Province and Incheon which reported 432 cases in total, other 25 cases were logged in five major cities and provinces outside of the Greater Seoul area.

Of some 4,066 members of the church, health officials have located 3,436, but other 630 people could not be reached.

The positivity rate for COVID-19 at the church stood at 15 percent, as 383 people had tested positive among 2,500 people who underwent testing.

“The positivity rate of Sarang Jeil Church is very high, which requires swift tests and isolation. But we are in a difficult situation to conduct the needed testing and isolation on the people whom we still can’t confirm contact details or remain out of contact,” Kim said.

Making the situation worse, two church members attempted to flee after testing positive.

A man in his 50s escaped from a hospital in Paju, Gyeonggi Province, on Tuesday after being placed under treatment. He was founded to have attended a church service on Aug. 9. Police are working on tracking him down.

On Monday, a woman in her 40s was caught by police after trying to make a getaway ahead of a transfer to a hospital from her home in Pohang, North Gyeongsang Province. She had stayed at the church for nearly five months before going back to Pohang on Thursday. She had symptoms of a cough and fever when she attended the anti-government rally on Saturday.

“Those who refuse to get treated or flee could face criminal punishment as they violate isolation measures,” Kim said.

Some municipalities began working with police to track down participants of the anti-government rallies and other church members with unknown whereabouts.

When health authorities had difficulties in locating members of the Shincheonji Church of Jesus, the single largest infection cluster so far, in February and March, police set up a joint team comprising over 8,500 police officers across the country to track down 9,000 people.

For those unable to be reached by health officials by phone, police will analyze surveillance footage, as well as details of their use of credit cards and cellphones.

But a bumpy road is expected for police investigations as some protesters reportedly turned off their phones and used cash during the rallies in order to avoid contact tracing.

By Park Han-na (hnpark@heraldcorp.com)