Abstract
Objectives: mask-wearing outside the home has been almost universal in Hong Kong since late January 2020 with very high compliance. Nevertheless, community spread of COVID-19 has still occurred. We aimed to assess the settings where COVID-19 transmission occurred and determine the fraction of transmission events that occurred in settings where masks are not usually worn.
Methods: we reviewed detailed information provided by the Hong Kong Department of Health on local COVID-19 cases diagnosed up to 30 September 2020 to determine the most likely settings in which transmission occurred. We classified them in probably mask-on or mask-of and compared the prevalence of asymptomatic infections in these settings.
Results: among the 2425 cases (65.3%, 2425/3711) with information on transmission setting, 77.6% of the transmission occurred in household and social settings where face masks are not usually worn. Infections that occurred in mask-on settings were more likely to be asymptomatic (adjusted odds ratio 1.33; 95% confidence interval: 1.04, 1.68).
Conclusions: we conclude that universal mask-wearing can reduce transmission, but transmission can continue to occur in settings where face masks are not usually worn. The higher proportion of asymptomatic cases in mask-on settings could be related to a milder disease presentation or earlier case detection.
Keywords: COVID-19; Epidemiology; Face masks; Public health; SARS-CoV-2; Transmission.
【저자키워드】 COVID-19, public health, SARS-CoV-2, Epidemiology, Transmission, Face masks, 【초록키워드】 public health, Masks, Local, Transmission, Mask, asymptomatic infections, Prevalence, Asymptomatic, asymptomatic infection, Compliance, Community, Asymptomatic case, Face masks, Asymptomatic cases, Hong Kong, information, disease, Face mask, COVID-19 transmission, face, adjusted odds ratio, 95% confidence interval, COVID-19 case, fraction, Department, Public, event, spread of COVID-19, occurred, proportion, diagnosed, provided, determine, occur, reduce,