Facts

“The medical community agrees that breathborne infectious materials can be spread with exhaled aerosols and that asymptomatic people, i e , those showing no symptoms, could be unknowingly infectious With the current worldwide pandemic of the respiratory coronavirus disease 2019 (COVID-19), various health bodies and governments are recommending that the population wear some form of mask or improvised facial covers while out in public in an effort to reduce the spread of disease.”

Pleil, Joachim D.; Beauchamp, Jonathan D.; Risby, Terence H.; Dweik, Raed A. Journal of breath research ; 2020

“Placing a surgical mask on an infected patient (respiratory source control) may offer a health-care worker (HCW) more protection than donning an N95 respirator (receiver protection).

A Vaseline-sealed N95 respirator on the receiver offered less protection when compared with any mask on the source. Respiratory source control can offer more protection to HCW and potentially decrease the spread of aerosolized infections.”

Journal of Aerosol Medicine and Pulmonary Drug Delivery Vol. 26, No. 3 (2013)

Respiratory source control using a surgical mask: an in vitro study. This study quantified the effectiveness of surgical masks as a means of source control in terms of reducing exposure to others. Source control (mask on the Source) was often 3-300 times more effective than a mask on the Receiver.

Rajeev B. Patel, Shaji D. Skaria, Mohamed M. Mansour & Gerald C. Smaldone (2015) Journal of Occupational and Environmental Hygiene, DOI: 10.1080/15459624.2015.1043050

“Primary benefits of wearing a mask include limiting the spread of the virus from someone who knows or does not know they have an infection to others. Masks also remind others to continue practicing physical distancing.”

Desai AN, Aronoff DM. Masks and Coronavirus Disease 2019 (COVID-19). JAMA. Published online April 17, 2020. doi:10.1001/jama.2020.6437

“Strategies for limiting the spread of influenza viruses in the community.”

“Symptomatic persons who cannot stay home during the acute phase of their illness, consideration should be given to having them wear a mask in public places when they may have close contact with other persons.”

CDC Interim Guidance for the Use of Masks to Control Seasonal Influenza Virus Transmission. Guidelines and Recommendations (accessed 4/15/2020)

Journal of Aerosol Medicine and Pulmonary Drug Delivery Vol. 26, No. 3 (2013)

Wearing masks outside the home in a reference period corresponding to the 2 weeks before symptom onset for cases was significantly protective against clinical SARS. Supporting the validity of this finding, there was a dose-response effect: by multivariable analysis, persons who always wore masks had a 70% lower risk of being diagnosed with clinical SARS compared with those who never wore masks, and persons with intermittent mask use had a 60% lower risk.

Finding: Consistent mask use lowered the risk for disease, thus providing some justification for the use of a strategy that was very popular in the general community.

Wu J, Xu F, Zhou W, et al. Risk Factors for SARS among Persons without Known Contact with SARS Patients, Beijing, China. Emerging Infectious Diseases. 2004;10(2):210-216. doi:10.3201/eid1002.030730

“Results indicate that surgical face masks could prevent transmission of human coronaviruses and influenza viruses from symptomatic individuals.”

Study included SARS-CoV-2

Leung, N.H.L., Chu, D.K.W., Shiu, E.Y.C. et al. Respiratory virus shedding in exhaled breath and efficacy of face masks. Nat Med (2020)

“This document provides the ECDC opinion on the suitability of face masks and other face covers in the community by individuals who are not ill in order to reduce potential pre-symptomatic or asymptomatic transmission of COVID-19 from the mask wearer to others.”

European Centre for Disease Prevention and Control. Using face masks in the community. Stockholm: ECDC; 2020

“Source control via surgical masks may be an important adjunct defense against the spread of respiratory infections. The fit of the mask or respirator, in combination with the airflow patterns in a given setting, are significant contributors to source control efficacy. Future clinical trials should include a surgical mask source control arm to assess the contribution of source control in overall protection against airborne infection.”

Journal of Occupational and Environmental Hygiene 2016 Jul 2; 13(7): 569–576.

“Because most of the penetrated particles entered through the face seal, the priority in respirator/mask development should be shifted from improving the efficiency of the filter medium to establishing a better fit that would eliminate or minimize face seal leakage.”Center for Health-Related Aerosol Studies, Department of Environmental Health, University of Cincinnati, Cincinnati, Ohio 45267-0056, USA.

Journal of Occupational and Environmental Hygiene 2009 Oct;6(10): 593-603

SARS Transmission, Risk Factors, and Prevention in Hong Kong (2003) SARS-CoV-1“Frequent mask use in public venues, frequent hand washing, and disinfecting the living quarters were significant protective factors (OR 0.36 to 0.58)”

SARS Transmission, Risk Factors, and Prevention in Hong Kong Joseph T.F. Lau, Hiyi Tsui, Mason Lau, Xilin Yang Emerg Infect Dis. 2004 Apr; 10(4): 587–592. doi: 10.3201/eid1004.030628 PMCID: PMC3323085

Instant hand wiping using a wet towel soaked in water containing 1.00% soap powder, 0.05% active chlorine, or 0.25% active chlorine from sodium hypochlorite removed 99.98% of the virus from hands. N95 masks, medical masks, and homemade masks made of four‐layer kitchen paper and one‐layer cloth could block 99.98%, 97.14%, and 95.15% of the virus in aerosols.

Journal of Medical Virology 31 March 2020

This study examined whether use of face masks and hand hygiene reduced the incidence of influenza-like illness (ILI). Observed significant reductions in ILI during weeks 4-6 in the mask and hand hygiene group, compared with the control group, ranging from 35% (confidence interval [CI], 9%-53%) to 51% (CI, 13%-73%), after adjusting for vaccination and other covariates. Face mask use alone showed a similar reduction in ILI compared with the control group, but adjusted estimates were not statistically significant. Neither face mask use and hand hygiene nor face mask use alone was associated with a significant reduction in the rate of ILI cumulatively.

J Infect Dis. 2010 Feb 15;201(4):491-8. doi: 10.1086/650396.

ClinicalTrials.gov identifier: NCT00490633.