Introduction Current SARS-CoV-2 containment measures rely on controlling viral transmission. Effective prioritization can be determined by understanding SARS-CoV-2 transmission dynamics. We conducted a systematic review and meta-analyses of the secondary attack rate (SAR) in household and healthcare settings. We also examined whether household transmission differed by symptom status of index case, adult and children, and relationship to index case. Methods We searched PubMed, medRxiv, and bioRxiv databases between January 1 and July 25, 2020. High-quality studies presenting original data for calculating point estimates and 95% confidence intervals (CI) were included. Random effects models were constructed to pool SAR in household and healthcare settings. Publication bias was assessed by funnel plots and Egger's meta-regression test. Results 43 studies met the inclusion criteria for household SAR, 18 for healthcare SAR, and 17 for other settings. The pooled household SAR was 18.1% (95% CI: 15.7%, 20.6%), with significant heterogeneity across studies ranging from 3.9% to 54.9%. SAR of symptomatic index cases was higher than asymptomatic cases (RR: 3.23; 95% CI: 1.46, 7.14). Adults showed higher susceptibility to infection than children (RR: 1.71; 95% CI: 1.35, 2.17). Spouses of index cases were more likely to be infected compared to other household contacts (RR: 2.39; 95% CI: 1.79, 3.19). In healthcare settings, SAR was estimated at 0.7% (95% CI: 0.4%, 1.0%).

ClinicalTrials.gov; No.: NCT02497729; URL: www.clinicaltrials.gov.

A COVID-19 outbreak occurred in the Diamond Princess cruise ship and we sampled environmental surfaces after passengers and crews vacated the cabins. SARS-CoV-2 RNA was detected from 58 out of 601 samples (10%) from case-cabins 1-17 days after the cabins were vacated, but not from non-case-cabins. There was no difference in the detection proportion between cabins for symptomatic (15%, 28/189, Cq: 29.79-38.86) and asymptomatic cases (21%, 28/131, Cq: 26.21-38.99). No SARS-CoV-2 virus was isolated from any of the samples. Transmission risk of SARS-CoV-2 from symptomatic and asymptomatic patients may be similar and environmental surfaces could be involved in viral transmission.

We report early findings from COVID-19 cases in Brunei suggesting a remarkably high proportion of asymptomatic (12%) and presymptomatic (30%) cases. This proportion was even higher in imported cases. These have implications for measures to prevent onward local transmission and should prompt reconsideration of current testing protocols and safe de-escalation of social distancing measures.