SINGAPORE — A link between two Covid-19 church clusters, where the source of infection had previously eluded the authorities, was finally established. This was done through a serological test, a new testing method developed by Duke-NUS Medical School. 

The test is able to detect past infections in someone who has recovered from it. Individuals who had contracted the coronovirus before will have high levels of virus-specific antibodies in their blood which can be picked up by this test.  

The authorities ran this test on Case 83, a 54 year-old Singaporean man, and Case 91, a 58-year-old Singaporean woman and the latest case to be announced on Tuesday (Feb 25). They then discovered that both of them had earlier contracted Covid-19 but were not detected at the time.

They also found that the two, who are married, had a link with another married couple from Wuhan (Cases 8 and 9) who had visited Life Church and Missions Singapore. Both couples were there on the same day on Jan 19.

Case 91, the wife, developed symptoms on Jan 23 and Case 83, the husband, had symptoms on Jan 28.

On Jan 25, both of them attended a Chinese New Year gathering on Mei Hwan Drive near Ang Mo Kio Ave 1 which other confirmed cases attended, including Case 66, a 28-year-old Singaporean man who worked at Grace Assembly of God church. 

On Feb 1, 6 and 10, the wife sought treatment at a general practitioner (GP) clinic.

At the same time, records also showed that her husband had gone to see a GP repeatedly on Feb 1, 5, 6 and 10. 

During the period under investigations later, the couple were not sick and did not show symptoms, but records by the Ministry of Health (MOH) showed that the wife had gone to the emergency department of Sengkang General Hospital earlier on Jan 26 with symptoms consistent with Covid-19. 

She was not marked as a suspect case at the time because she had no recent travel history to China. The case definition has since been expanded to include those who have not been to China in the last 14 days.

On Feb 18, both of them showed up at the National Centre for Infectious Diseases to undergo tests, including the serological tests. It was then confirmed that they had earlier been infected with the virus. On Feb 19, results showed that the husband had Covid-19 while results for the wife were confirmed on Feb 22.

Together with help from the police doing contact tracing, the authorities found that the Chinese New Year gathering on Mei Hwan Drive was the common event that this Singaporean couple attended together with Case 66 from the Grace Assembly of God church.

As of Tuesday, there are 23 cases from the Grace Assembly of God cluster — making it the biggest cluster — and seven cases from Life Church and Missions Singapore in Paya Lebar. 

Associate Professor Kenneth Mak, director of medical services at MOH, said that the serological tests gave the authorities the confidence to establish that the cases reported at the Grace Assembly of God cluster was not a case of widespread community transmission from other sources.

Rather, it was a result of a sequential series of events, he said at a media briefing on Tuesday by the multi-ministry task force managing the public health crisis.

MOH said that the spread between the clusters started with Case 8 (a 56 year-old woman) and Case 9 (a 56 year-old man), who are Chinese nationals. 

The couple arrived in Singapore on Jan 19 from Wuhan, China — the epicentre of the outbreak.  

They likely infected the Singaporean couple who went on to pass the infection to Case 66 at the Chinese New Year gathering, the ministry said. Case 66 later passed the infection to his colleagues at Grace Assembly of God church.

Case 66 was thus found to be the primary case in the Grace Assembly of God cluster. 

Some people were exposed to him at a staff meeting at the Tanglin branch of the church and they in turn infected other church members, MOH said. 

Writing on Facebook, Prime Minister Lee Hsien Loong said that the authorities “discovered an important link” between two existing clusters, including the biggest cluster at Grace Assembly of God. 

He noted that Cases 83 and 91 had only mild symptoms earlier and had not been diagnosed with Covid-19. But the new serological test later confirmed that they had been infected earlier, and linked the two clusters together. 

“This breakthrough would not have been possible without close cooperation among the Ministry of Health, Singapore Police Force and researchers from Duke-NUS Medical School, who developed the serological test, the world's first, here in Singapore. My thanks to all of you for a job well done!” he added.