At least 10 here got infected from those showing no symptoms: Study
At least 10 people in Singapore got the coronavirus from those without symptoms, according to a new study of such patients here.
It was published by the United States' Centres for Disease Control and Prevention on Wednesday and co-authored by Associate Professor Vernon Lee, director of communicable diseases at the Ministry of Health (MOH).
The study focused on the pre-symptomatic transmission of Sars-CoV-2, the virus that causes Covid-19.
Pre-symptomatic transmission refers to an incident in which a disease is passed from one individual to another, despite the first person not showing any symptoms of the illness.
The risk that such transmission poses has been a source of great concern, especially because many measures to curb the virus' spread, such as temperature screening, rely on symptoms showing in an infected individual.
The study had examined the Covid-19 cases reported in Singapore between Jan 23 and March 16, focusing on cases that were in clusters.
Of the 157 non-imported cases in this period, 10 could be attributed to pre-symptomatic transmission, the study found.
Three of the 10 were from the Grace Assembly of God and The Life Church and Missions Singapore cluster, and had attended church service on Jan 19 - the same day as an infected pair of tourists from Wuhan, who had not shown symptoms then.
One of the three cases, a 52-year-old woman, had sat in the same seat that one of the tourists had occupied earlier in the day.
Among the 10 cases, one occurred as a result of the Safra Jurong cluster.
A 54-year-old woman who had been exposed to a confirmed case at the Safra Jurong dinner on Feb 15 attended the same singing class as another woman, 63, on Feb 24.
Both later developed symptoms of the virus.
In seven of the 10 cases, pre-symptomatic transmission exposure occurred one to three days before the source patient developed symptoms.
The researchers said containment measures should include the period before the onset of symptoms when carrying out contact tracing, and that the findings also highlight the importance of social distancing.
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