SARS-CoV-2 transmission in different settings: Analysis of cases and close contacts from the Tablighi cluster in Brunei Darussalam
SARS-CoV-2 transmission in different settings: Analysis of cases and close contacts from the Tablighi cluster in Brunei Darussalam. Spencer EA, Heneghan C.
Published on July 23, 2020
Transmission Dynamics of COVID-19
For 71 cases observed in Brunei, factors associated with higher onward transmission among 1,755 close contacts were attendance at local religious gatherings and household contact. Workplace and social setting transmission was low.
75 individuals in Brunei attended a Tablighi Jama’at event in Malaysia. Of these, 19 subsequently tested positive for SARS-CoV-2. 52 locally transmitted cases developed subsequently. The resulting cluster of 71 cases was investigated for 1,755 close contacts.
The highest non-primary attack rates were observed at a subsequent local religious gathering: 15% (95% CI, 7.1% to 28%) and in the household: 11% (95%CI 7.3% to 15%).
Within households, the attack rate was 14% (95%CI 8.8% to 20%) for symptomatic cases, and 4.4% (95% CI, 0.0% to 11%) for asymptomatic cases and 6.1% (95%CI 0.3% to 12%) for presymptomatic cases.
An attack rate of less than 1% was observed for workplaces and social settings.
What did they do?
The first case identified in Brunei was interviewed and contacts traced. It became clear that a number of cases had developed after attending a Tablighi Jama’at gathering in Malaysia. This transmission was investigated.
A close contact was defined as any person living in the same household, or someone within one
metre of a confirmed case in an enclosed space for more than 15 minutes.
All close contacts of confirmed cases were tested with RT-PCR. Those who tested positive were admitted to the national isolation centre.
Those who tested negative were placed under home quarantine for 14 days from last exposure
to the confirmed case. For individuals under home quarantine, their compliance and health status were monitored daily, through video calls or face-to-face assessments. Those who developed symptoms during home quarantine were re-tested.
This was a comprehensive study of a cluster of 71 cases and their close contacts in a relatively controlled context; therefore we expect information to be comprehensive. As with all retrospectively collected data, bias may affect individuals’ recall of exposures.
|Clearly defined setting
||Demographic characteristics described
||Follow-up length was sufficient
||Transmission outcomes assessed
||Main biases are taken into consideration
What else should I consider?
Brunei’s small population (<500,000) and comprehensive contact tracing procedures allowed thorough study of new case arrivals and transmission. Tablighi gatherings are large international (religious) events of several days’ duration and include communal prayers, shared meals and often shared accommodation. While moderate physical distancing was implemented in Brunei there was no community quarantine or lockdown, public services and businesses remained open, and no internal movement restrictions were imposed.
The authors propose differentiated testing strategies that account for transmission risk.
World Health Organization. The First Few X (FFX) Cases and contact investigation 504 protocol for 2019-novel coronavirus (2019-nCoV) infection, version 2. 2020
About the authors
Carl is Professor of EBM & Director of CEBM at the University of Oxford. He is also a GP and tweets @carlheneghan. He has an active interest in discovering the truth behind health research findings
Dr Elizabeth Spencer; MMedSci, PhD. Epidemiologist, Nuffield Department for Primary Care Health Sciences, University of Oxford.