ABSTRACT
Background Studies on the early introduction of SARS-CoV-2 in a naive population have important epidemic control implications. We report findings from the epidemiological investigation of the initial 135 COVID-19 cases in Brunei and describe the impact of control measures and travel restrictions. Methods Epidemiological and clinical information were obtained for all confirmed COVID-19 cases in Brunei, whose symptom onset was from March 9 to April 5, 2020 (covering the initial 5 weeks of the epidemic). Transmission-related measures such as reproduction number (R), incubation period, serial interval were estimated. Time-varying R was calculated to assess the effectiveness of control measures. Results A total of 135 cases were detected, of which 53 (39.3%) were imported. The median age was 36 years (range = 0.5 to 72). 41 (30.4%) and 13 (9.6%) were presymptomatic and asymptomatic cases respectively. The median incubation period was 5 days (IQR = 5, range = 1 to 11), and the mean serial interval was 5.39 days (sd = 4.47; 95% CI: 4.25, 6.53). R0 was between 3.88 and 5.96, and the doubling time was 1.3 days. By the 13th day of the epidemic, the Rt was under one (Rt = 0.91; 95% credible interval: 0.62, 1.32 ) and the epidemic was under control. Conclusion Epidemic control was achieved through a combination of public health measures, with emphasis on a test-isolate-trace approach supplemented by travel restrictions and moderate physical distancing measures but no actual lockdown. To maintain suppression, regular and ongoing testing of high-risk groups can supplement the existing surveillance program.
Subject(s)
COVID-19ABSTRACT
We report the transmission dynamics of SARS-CoV-2 across different settings from the initial COVID-19 cluster in Brunei, arisen from 19 attendees at the Malaysian Tablighi Jamaat gathering and resulted in 52 locally transmitted cases. Highest non-primary attack rates(ARs) were observed at a subsequent local religious gathering (14.8% [95%CI: 7.1,27.7]) and in the household (10.6% [95%CI: 7.3,15.1]. Household ARs of symptomatic cases were higher (14.4% [95%CI: 8.8,19.9]) than asymptomatic (4.4% [95%CI: 0.0,10.5]) or presymptomatic cases (6.1% [95%CI: 0.3,11.8]). Low ARs (<1%) were observed for workplace and social settings. Our analysis highlights that SARS-CoV-2 transmission varies depending on environmental, behavioural and host factors. We identify red flags of potential super-spreading events, namely densely populated gatherings for prolonged periods in enclosed settings, presence of individuals with recent travel history, and group behaviours such as communal eating, sleeping and sharing of personal hygiene facilities. We propose differentiated testing strategies that account for transmission risk. Article summary lineWe highlight the variability of SARS-CoV-2 transmission across different settings, identify settings at highest risk, and characterize the role of environmental, behavioural, and host factors in driving SARS-CoV-2 transmission.