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

Investigation of three clusters of COVID-19 in Singapore: implications for surveillance and response measures

Rachael Pung  1 , Calvin J Chiew  1 , Barnaby E Young  2 , Sarah Chin  1 , Mark I-C Chen  3 , Hannah E Clapham  4 , Alex R Cook  4 , Sebastian Maurer-Stroh  5 , Matthias P H S Toh  6 , Cuiqin Poh  1 , Mabel Low  1 , Joshua Lum  1 , Valerie T J Koh  1 , Tze M Mak  7 , Lin Cui  7 , Raymond V T P Lin  7 , Derrick Heng  1 , Yee-Sin Leo  8 , David C Lye  9 , Vernon J M Lee  10 ; Singapore 2019 Novel Coronavirus Outbreak Research Team
Collaborators, Affiliations

Investigation of three clusters of COVID-19 in Singapore: implications for surveillance and response measures

Rachael Pung et al. Lancet. .

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.

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Figures

Figure 1
Figure 1
Timing of events and cases in three clusters of COVID-19 in Singapore Age and sex are shown for each case (left panels), with other pertinent information (eg, relationship or nationality). Timeline of events (right panels); onset dates of symptomatic cases are shown, when available. COVID-19=coronavirus disease 2019.
Figure 2
Figure 2
Incubation periods for cases with known probable exposure times Median (IQR) time to onset was 4 days (IQR 3–6).
Figure 3
Figure 3
Probable secondary cases arising from each COVID-19 case COVID-19=coronavirus disease 2019.
See this image and copyright information in PMC

References

    1. Wuhan Municipal Health Commission Report on current pneumonia epidemic situation in the city. (In Chinese.) Dec 31, 2019. http://wjw.wuhan.gov.cn/front/web/showDetail/2019123108989
    1. The State Council, People's Republic of China Wuhan novel coronavirus prevention and control command notice (no 1). (In Chinese.) Jan 23, 2020. http://www.gov.cn/xinwen/2020-01/23/content_5471751.htm
    1. DW.com. Wuhan pneumonia virus continues to spread, Hubei orders 15 cities to be closed. (In Chinese.) Jan 24, 2020. https://www.dw.com/zh/a-52132769
    1. World Health Organization Statement on the second meeting of the International Health Regulations (2005) Emergency Committee regarding the outbreak of novel coronavirus (2019-nCoV) Jan 30, 2020. https://www.who.int/news-room/detail/30-01-2020-statement-on-the-second-...
    1. World Health Organization Coronavirus disease 2019 (COVID-2019): situation report—33. Feb 22, 2020. https://www.who.int/docs/default-source/coronaviruse/situation-reports/2...

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