key: cord-0950464-q8faf17k
authors: Ng, Qin Xiang; De Deyn, Michelle Lee Zhi Qing; Yeo, Wee Song
title: Do face masks help? is not the question
date: 2020-11-03
journal: Proc Natl Acad Sci U S A
DOI: 10.1073/pnas.2012241117
sha: 5229c4a5e0cccdb79aad24eeadd6494b94c58e72
doc_id: 950464
cord_uid: q8faf17k

nan

and enforcement is purely at the discretion of local jurisdictions. We know that "socially responsible" behaviors may not be intuitive and, as with health behavior change, take time. It is thought that it takes anywhere between 18 and 254 d to develop a new habit (5) .

Second, Zhang et al. (1) oversimplify the day-to-day fluctuations and erroneously applied linear regression to the data between 17 April and 9 May in NYC and between 5 April and 9 May in the United States. Linear regression should be limited to variables with a linear relationship (6) . In the case of COVID-19, modeling the disease rate as the virus spreads in the community is complex. The researchers used best-fit lines to support a decreasing rate in the daily new infections; we would advise caution in interpreting these linear regressions. Nonlinear regression analysis, or a more explicitly epidemiological model such as EpiEstim (7), would be more appropriate.

It is too premature to discount the preventive benefits of social distancing in favor of face masks. We do certainly hope that properly worn face masks help stem the spread of the coronavirus, and there is growing evidence to support the recommendation to wear masks in public spaces (8) . However, ensuring public compliance is in itself a difficult task. In Singapore, stringent laws were put in place to enforce wearing face masks in public and work spaces; first-time offenders would be fined while egregious cases could be prosecuted in court (9) .

Identifying airborne transmission as the dominant route for the spread of COVID-19

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The incubation period of coronavirus disease 2019 (COVID-19) from publicly reported confirmed cases: Estimation and application

Who's enforcing mask rules? Often retail workers, and they're getting hurt

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Singapore 099253; b Department of Medicine, James Cook University Hospital, Middlesbrough TS4 3BW, United Kingdom; and c Department of Pediatric Medicine, Mount Elizabeth Hospital

Understanding and checking the assumptions of linear regression: A primer for medical researchers

Improved inference of time-varying reproduction numbers during infectious disease outbreaks

Community use of face masks and COVID-19: Evidence from a natural experiment of state mandates in the US

A tale of two cities: A comparison of Hong Kong and Singapore's early strategies for the Coronavirus Disease 2019 (COVID-19)