When everyone in a group is masked, COVID-19 transmission plunges
When sick wear medical masks, airborne particles in a room decrease by 94%; cotton masks decrease particles 88%
We recruited adult volunteers with confirmed influenza and suspected cases of coronavirus disease 2019 (COVID-19) to wear medical masks and self-designed triple-layer cotton masks in a regular bedroom and a car with air conditioning. Four 1-hour repeated measurements (two measurements for bedroom the others for car) of particles with a size range of 20–1000 nm measured by number concentrations (NC0.02–1), temperature and relatively humidity, and cough/sneeze counts per hour were conducted for each volunteer. The test results showed that filtration efficiency were 86.4% and 99.9% at 5.5 cm/s velocity for our cotton mask and 3M medical mask, respectively. The mean concentrations of particles with a size range of 20-1000 nm measured by number concentrations for background (without volunteer), without mask, with medical mask, and with cotton mask were 51,044 particles/cm3, 92,634 particles/cm3, 53,423 particles/cm3, and 55,877 particles/cm3, respectively in a bedroom and 22,874 particles/cm3, 122,182 particles/cm3, 25,733 particles/cm3, and 26,453 particles/cm3, respectively in a car. The mean concentrations of particles for the volunteers wearing no mask were significantly higher than the background concentrations and the concentrations of particles for the volunteers wearing medical masks or cotton masks in a bedroom and in a car.
Shopping, office work and indoor gatherings of less than 10 people may not significantly increase COVID-19 risk; restaurants increased odds by 280%, bars by 390%
To assess community and close contact exposures associated with COVID-19, exposures reported by case-patients (154) were compared with exposures reported by control-participants (160). Case-patients were symptomatic adults (persons aged ≥18 years) with SARS-CoV-2 infection confirmed by reverse transcription–polymerase chain reaction (RT-PCR) testing. Control-participants were symptomatic outpatient adults from the same health care facilities who had negative SARS-CoV-2 test results. Close contact with a person with known COVID-19 was more commonly reported among case-patients (42%) than among control-participants (14%). No significant differences were observed in the bivariate analysis between case-patients and control-participants in shopping; gatherings with ≤10 persons in a home; going to an office setting; going to a salon; gatherings with >10 persons in a home; going to a gym; using public transportation; going to a bar/coffee shop; or attending church/religious gathering. When the analysis was restricted to the 225 participants who did not report recent close contact with a person with known COVID-19, case-patients were more likely than were control-participants to have reported dining at a restaurant (adjusted odds ratio = 2.8) or going to a bar/coffee shop (adjusted odds ratio = 3.9).
COVID-19 clusters 160% more likely in recreational ‘mask-off’ settings vs workplace ‘mask-on’ settings
We assessed the effect of community-wide mask usage to control coronavirus disease 2019 (COVID-19) in Hong Kong Special Administrative Region (HKSAR). Findings: The COVID-19 incidence in HKSAR (129.0 per million population) was significantly lower (p<0.001) than that of 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 compliance of face mask usage by HKSAR general public was 96.6%. We observed 11 COVID-19 clusters in recreational ‘mask-off’ settings compared to only 3 in workplace ‘mask-on’ settings.
Mask mandates in the US tied to reduced COVID-19 growth rate
The research design is an event study examining changes in the daily county-level COVID-19 growth rates between March 31 and May 22, 2020. Mandating face mask use in public is associated with a decline in the daily COVID-19 growth rate by 0.9, 1.1, 1.4, 1.7, and 2.0 percentage points in 1-5, 6-10, 11-15, 16-20, and 21 or more days after state face mask orders were signed, respectively. Estimates suggest that as a result of the implementation of these mandates, more than 200,000 COVID-19 cases were averted by May 22, 2020.
Individual mask-wearing shrinks COVID-19 risk, reduces severity
Individual mask-wearing reduces transmission of COVID-19 and similar viruses by 85% according to meta-analysis; 1 meter distancing reduces transmission 82%
We did a systematic review and meta-analysis to investigate the optimum distance for avoiding person-to-person virus transmission and to assess the use of face masks and eye protection to prevent transmission of viruses. We obtained data for SARS-CoV-2 and the betacoronaviruses that cause severe acute respiratory syndrome, and Middle East respiratory syndrome from 21 standard WHO-specific and COVID-19-specific sources. Our search identified 172 observational studies across 16 countries and six continents, with no randomised controlled trials and 44 relevant comparative studies in health-care and non-health-care settings (n=25,697 patients). Transmission of viruses was lower with physical distancing of 1 meter or more, compared with a distance of less than 1 meter (pooled adjusted odds ratio 0·18); protection was increased as distance was lengthened (change in relative risk 2·02 per meter). Face mask use could result in a large reduction in risk of infection (adjusted odds ratio 0·15), with stronger associations with N95 or similar respirators compared with disposable surgical masks or similar. In a subgroup analysis comparing N95 respirators with surgical or similar masks (eg, 12–16-layer cotton), the association was more pronounced in the N95 group (aOR 0·04) compared with other masks (0·33).
Individual mask-wearing reduces odds of COVID-19 by 96% according to meta-analysis
A total of 21 studies met our inclusion criteria. Meta-analyses suggest that mask use provided a significant protective effect (OR = 0.35 and 95% CI = 0.24-0.51). Use of masks by healthcare workers (HCWs) and non-healthcare workers (Non-HCWs) can reduce the risk of respiratory virus infection by 80% (OR = 0.20, 95% CI = 0.11-0.37) and 47% (OR = 0.53, 95% CI = 0.36-0.79). The protective effect of wearing masks in Asia (OR = 0.31) appeared to be higher than that of Western countries (OR = 0.45). Masks had a protective effect against influenza viruses (OR = 0.55), SARS (OR = 0.26), and SARS-CoV-2 (OR = 0.04). In the subgroups based on different study designs, protective effects of wearing mask were significant in cluster randomized trials and observational studies.
Individual mask-wearing reduces risk of COVID-19 by 88% according to meta-analysis
A systematic search up to October 2020. There was two search strategy; for airborne transmission and the role of face mask for prevention of SARS-CoV-2 infection. Results: After eligibility assessment, four articles with a total of 7688 participants were included in this meta-analysis. The result of this meta-analysis has shown significant reduction in infection with face mask use; the pooled risk ratio was 0.12. Conclusion: In conclusion, this meta-analysis suggests that there is association between face mask use and reduction of COVID-19.
Individual mask-wearing reduces COVID-19 risk by 66%; in addition, infections that do occur are milder, according to meta-analysis
A meta-analysis of 29 studies on infection with SARS-CoV-2, SARS, or MERS revealed that type N-95 masks (corresponding approximately to FFP-2), surgical masks, or similar multilayer cotton masks can greatly reduce the infection risk for the wearers (risk ratio 0.34). Model experiments and case reports suggest that masks covering the mouth and nose afford considerable protection against transmission of SARS-CoV-2 and other airborne diseases by reducing release of and exposure to potentially infectious droplets; in addition, infections that do occur take a milder course.
When it comes to choosing a mask, fit may be as important as fabric
Significant gaps on a mask can reduce the filtration efficiency by 33%
This study evaluated the fitted filtration efficiency of 7 consumer-grade masks and five procedure mask modifications. The mean filtration efficiency of consumer-grade face masks tested in this study ranged from 79.0% to 26.5%, with the washed, 2-layer nylon mask having the highest filtration efficiency and the 3-layer cotton mask having the lowest. The cotton bandana folded into a multilayer rectangle affixed to the ears with rubber bands, as described by the US Surgeon General, provided a mean filtration efficiency of 49.9%. Folding the bandana bandit style produced a similar result (mean filtration efficiency, 49.0%). The tested mean filtration efficiency of the single-layer polyester gaiter/neck cover balaclava bandana was 37.8%. The single-layer polyester/nylon mask, which is attached with tie strings, tested at a mean filtration efficiency of 39.3%. The polypropylene mask with nonelastic (fixed) ear loops tested at a mean filtration efficiency of 28.6%. As expected based on data from our previous work, a National Institute for Occupational Safety and Health–approved 3M 9210 N95 respirator used as a reference control provided very high mean filtration efficiency (98.4%). The medical procedure masks with elastic ear loops tested in this study had a mean filtration efficiency of 38.5%, which was lower than that of medical surgical masks with tie strings (71.5%). Tying the ear loops and tucking in the corners of the procedure mask to minimize gaps in the sides of the mask increased the mean filtration efficiency to 60.3%.
Higher thread counts, increased layers, and visible raised fibers all improve filtration
Materials were microimaged and tested against size selected NaCl aerosol with particle mobility diameters between 50 and 825 nm. Three of the top five best performing samples were woven 100% cotton with high to moderate yarn counts, and the other two were woven synthetics of moderate yarn counts. In contrast to recently published studies, samples utilizing mixed materials did not exhibit a significant difference in the measured filtration efficiency when compared to the product of the individual filtration efficiency for the components. The filtration efficiency and differential pressure increased monotonically with the number of cloth layers for a lightweight flannel, suggesting that multilayered cloth masks may offer increased protection from nanometer-sized aerosol with a maximum filtration efficiency dictated by breathability. The best performing cloth materials had moderate yarn counts with visible raised fibers. No measured cloth masks performed as well as an N95.
Multi-layer cotton masks may have a filtration rate of over 90%
From the eleven studies selected, eight were laboratory-based studies, one non-randomized and one RCT supported by laboratory data. Between the evaluated fabrics only three presented a filtration efficiency > 90%. Hybrid of cotton/chiffon (95%CI 95.2 to 98.8), hybrid of cotton/silk (95%CI 92.2 to 95.8) and cotton quilt (95%CI 94.2 to 97.8). However, cloth masks are not recommended for healthcare workers. A meta-analysis was not feasible due to a high methodological heterogeneity. The overall quality of evidence ranged from very low to moderate. Despite the lower efficiency compared to medical masks, laboratorial results may underestimate the efficiency of cloth masks in real life. Cloth mask efficiency is higher when made of hybrid fabrics (cotton/chiffon, cotton/silk) and cotton quilt, mainly with multiple layers.
Nonmedical disposable masks may filter 33% more viral aerosols than 3 layer cotton, and is nearly as effective as N95, assuming identical fit
This study found that all the fabric masks had a viral filtration efficiency of at least 50% when tested against aerosols with an average size of 6.0 µm. The minimum viral filtration efficiency of fabric masks improved (to 63%) when the larger aerosols were excluded to give and average aerosol size of 2.6 µm, which better represents inhaled aerosols that can reach the lower respiratory system. The best performing fabric masks were the cotton mask with a section of vacuum cleaner bag (filtration efficiency of 2.6 µm= 98.8%) or a dried baby wipe (filtration efficiency of 2.6 µm = 97.6%) in the pocket designed for a disposable filter. The filtration efficiency of two surgical masks of 2.6 µm (99.5% and 98.5%) and a N95 masks (99.3%) were comparable to their advertised bacterial filtration efficacy. The filtration efficiency of a disposable face mask (nonmedical GB/T32610-2016) of 2.6 µm was 99.7%. The filtration efficiency of three layered masks made of 100% cotton of 2.6 µm was 65.8%. This research supports the use of fabric masks in the community to prevent the spread of SARS-CoV-2; however, future research is needed to explore the optimum design in ensuring proper fit. There is also a need for mass education campaigns to disseminate this information, along with guidelines around the proper usage and washing of fabric masks.