The role of community-wide wearing of face mask for control of coronavirus disease 2019 (COVID-19) epidemic due to SARS-CoV-2

Others Hygiene
Cheng VCC
J infect

Main result

In Hong Kong (HKSAR), the general population started wearing masks spontaneously in the early stages of the epidemic, and to assess the prevalence of this measure, 67 health professionals counted the number of people wearing masks among the first 50 people encountered on the home-hospital trip for three consecutive days (6 April to 8 April 2020, days 98-100 of the study, between 7 am and 9 am). The prevalence observed was 97.2%, 97.1%, and 95.7% over the three days for all 18 administrative districts of HKSAR.
Of the 961 COVID-19 patients diagnosed in total, 11 groups of 113 people were directly involved in activities without the use of masks (catering, karaoke, sports centers) versus 3 groups of 11 people identified as infected while working with protective masks. The number of infections in situations without masks was statistically higher (p=0.036).
The number of infections with COVID-19 is statistically lower in Hong Kong (129.0/million) than in states that do not use masks for the general population as an active measure against the spread of SARS-CoV-2, p<0.001 (Spain: 2983.2, Italy: 2250.8, Germany: 1241.5, France: 1151.6, U.S.: 1102.8, U.K.: 831.5, Singapore: 259.8 and South Korea: 200.5).


The study suggests that use of masks by the population at large might have reduced the incidence of SARS-CoV-2 at HKSAR.
The authors recommend the use of masks by the general population in public places while ensuring the provision of masks for health care workers. The use of cloth masks with reduced filtration efficiency is preferable to no masks at all in areas of high contamination risk. The use of masks by the population at large may reduce the transmission of SARS-CoV-2 by asymptomatic COVID-19 patients.

Strength of evidence Weak

1) A retrospective study of all COVID-19 patients diagnosed at HKSAR (n=961)
2) pre-proof article
3) no consideration was given to unmasked modes of transmission in the domestic environment
4. The types of masks used by the population and the hygiene practices adopted for the fitting and the removal of the masks were not examined.


Assessing the effect of population-wide mask use on the spread of SARS-CoV-2


A retrospective study conducted in Hong Kong (HKSAR) on all patients diagnosed positive for COVID-19 between December 31, 2019, and April 8, 2020 (first 100 epidemic days).
For each patient, an attempt was made to trace the source of infection to determine whether it was a masked or unmasked situation.
The incidence of COVID-19 contamination per million residents of HKSAR was compared to the incidence of other countries with a high-quality health care system and more than 100 cases of COVID-19 confirmed on day 72 of the study (the day WHO declared pandemic status) but which did not implement masking in the general population as an active measure to contain the epidemic.


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