Investigation of three clusters of COVID-19 in Singapore

Lancet. 2020 Mar 28;395(10229):1039-1046. doi: 10.1016/S0140-6736(20)30528-6. Epub 2020 Mar 17.

Pung R1, Chiew CJ1, Young BE2, Chin S1, Chen MI3, Clapham HE4, Cook AR4, Maurer-Stroh S5, Toh MPHS6, Poh C1, Low M1, Lum J1, Koh VTJ1, Mak TM7, Cui L7, Lin RVTP7, Heng D1, Leo YS8, Lye DC9, Lee VJM10; Singapore 2019 Novel Coronavirus Outbreak Research Team.

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Abstract BACKGROUND: Three clusters of coronavirus disease 2019 (COVID-19) linked to a tour group from China, a company conference, and a church were identified in Singapore in February, 2020. METHODS: We gathered epidemiological and clinical data from individuals with confirmed COVID-19, via interviews and inpatient medical records, and we did field investigations to assess interactions and possible modes of transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Open source reports were obtained for overseas cases. We reported the median (IQR) incubation period of SARS-CoV-2. FINDINGS: As of Feb 15, 2020, 36 cases of COVID-19 were linked epidemiologically to the first three clusters of circumscribed local transmission in Singapore. 425 close contacts were quarantined. Direct or prolonged close contact was reported among affected individuals, although indirect transmission (eg, via fomites and shared food) could not be excluded. The median incubation period of SARS-CoV-2 was 4 days (IQR 3-6). The serial interval between transmission pairs ranged between 3 days and 8 days. INTERPRETATION: SARS-CoV-2 is transmissible in community settings, and local clusters of COVID-19 are expected in countries with high travel volume from China before the lockdown of Wuhan and institution of travel restrictions. Enhanced surveillance and contact tracing is essential to minimise the risk of widespread transmission in the community. FUNDING: None. Copyright © 2020 Elsevier Ltd. All rights reserved.

PMID: 32192580 DOI: 10.1016/S0140-6736(20)30528-6