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Mystery behind Singapore's largest coronavirus infection cluster solved

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The mystery behind Singapore's largest coronavirus infection cluster - the Grace Assembly of God church - has been solved, using a new test that is able to detect past infections even in recovered patients.

[SINGAPORE] The mystery behind Singapore's largest coronavirus infection cluster - the Grace Assembly of God church - has been solved, using a new test that is able to detect past infections even in recovered patients.

Using a serological test developed by Singapore's Duke-NUS Medical School, contact tracers from the Ministry of Health and the police were able to track the infection to two travellers from Wuhan, who were Cases 8 and 9.

The Wuhan couple were linked to The Life Church and Missions cluster, a Chinese New Year family gathering in Mei Hwan Drive, and finally to the Grace Assembly of God, which to date is linked to 23 cases.

This is believed to be the first time clusters have been linked using serological tests.

The new test - which is done on a blood sample - can be used on patients who have recovered. The lab tests currently used to confirm infections, known as polymerase chain reaction (PCR) tests, detect the presence of viral genetic material in biological samples obtained from a patient, such as a saliva swab. It thus will not work if the patient has recovered.

The new test works by detecting antibodies the body produces in response to an infection. These antibodies can stay in the body for several years.

The Health Ministry said on Tuesday (Feb 25) that the Grace Assembly of God church cluster began with Case 66, a 28-year-old Singaporean who works at the church and also attended a family gathering in Mei Hwan Drive.

"Case 66 had reported onset of symptoms on Jan 29 - the earliest in the cluster - and had gone to work at Grace Assembly of God while symptomatic," said the ministry.

To determine how Case 66 had been infected, contact tracers investigated the locations he had visited and the people he had close contact with.

Investigations led them to a married couple, cases 83 and 91, who attended the same Chinese New Year family gathering and were also at the Life Church on the day the Wuhan couple - cases 8 and 9 - were there.

The couple had no symptoms at the time of the investigation, but records showed both had earlier sought medical treatment.

Case 91, a 58-year-old Singaporean with no recent travel history to China, was the only new case announced by MOH on Tuesday. Prior to hospitalisation, she had mostly stayed at her home in Rivervale Drive.

She had gone to Sengkang General Hospital on Jan 26 with symptoms consistent with Covid-19. She had also sought treatment at a general practitioner (GP) clinic on Feb 1, Feb 6 and Feb 10.

Case 83, meanwhile, had also repeatedly sought treatment at GP clinics in early February.

Based on this finding, the ministry's epidemiology team arranged for cases 83 and 91 to be tested at the National Centre for Infectious Diseases, including using serological tests developed by researchers from the Duke-NUS Medical School.

Their tests - conducted while they were well - confirmed they had earlier been infected.

"This meant that cases 83 and 91 likely got infected from cases 8 and 9 (Chinese nationals from Wuhan), and went on to pass the infection to Case 66 at the Chinese New Year gathering on Jan 25," said the ministry.

"Case 66 subsequently passed the infection to his colleagues at Grace Assembly of God."

On Tuesday, five more cases were discharged from hospital, bringing the total number of patients who have recovered to 58.

Of the 33 confirmed cases who are still in hospital, most are stable or improving. Seven are in critical condition in the intensive care unit.

THE STRAITS TIMES