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October 26, 2020

Preventing the Spread of SARS-CoV-2 With Masks and Other “Low-tech” Interventions

Author Affiliations
  • 1National Institute of Allergy and Infectious Diseases, Bethesda, Maryland
JAMA. 2020;324(19):1935-1936. doi:10.1001/jama.2020.21946

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of coronavirus disease 2019 (COVID-19), has caused a global pandemic of historic proportions in the 10 months since cases were first reported in Wuhan, China, in December 2019, with worldwide morbidity, mortality, and disruptions to society.

Ultimately, a safe and effective vaccine will be essential to control the pandemic and allow resumption of the many activities of normal life. While results of phase 3 trials for multiple candidate vaccines are on the near horizon, “low-tech” tools to prevent the spread of SARS-CoV-2 are essential, and it must be emphasized that these interventions will still be needed after a vaccine is initially available. Even if one or more vaccines have high efficacy and uptake in the population, it will take at least several months for enough people to be vaccinated to confer herd immunity on a population basis.

Modalities in the combination prevention “toolbox” against the spread of SARS-CoV-2 include wearing masks, physical distancing, hand hygiene, prompt testing (along with isolation and contact tracing), and limits on crowds and gatherings. If a vaccine has only moderate efficacy, or if vaccine uptake is low, these other modalities will be even more critical.

Wearing face coverings—masks—in the community setting to prevent the spread of SARS-CoV-2 is a key component of this combination approach. Multiple lines of evidence support the effectiveness of masks for the prevention of SARS-CoV-2 transmission. Mandates for the wearing of masks in public have been associated with a decline in the daily growth rate of COVID-19 cases in the US. The implementation of such mandates averted more than 200 000 cases of COVID-19 by May 22, 2020, according to modeling estimates.1

Randomized clinical trials of community mask use are challenging to conduct because of ethical and practical considerations. Observational studies have substantial limitations but can be instructive. For example, a study of secondary SARS-CoV-2 transmission in 124 Chinese households found that mask wearing at home by 1 or more family members before the onset of symptoms in the primary case was associated with a lower odds of secondary transmission (adjusted odds ratio, 0.21 [95% CI, 0.06-0.79]).2 In a study at a US academic medical center, after the implementation of universal mask use for all health care workers and patients, the SARS-CoV-2 positivity rate among health care workers declined from 14.65% to 11.46%, with a decline of 0.49% per day.3

To understand the rationale for mask wearing to prevent SARS-CoV-2 transmission, it is helpful to understand how the virus spreads from person to person. SARS-CoV-2 is primarily transmitted by respiratory droplets exhaled by infected individuals; these droplets span a spectrum of sizes. Larger droplets fall out of the air relatively quickly while close to the source, usually within a 6-foot distance. Smaller droplets, often referred to as aerosols, are also present at close range but may remain in the air over time and greater distances, decreasing in concentration as they move outward from their source.4

The epidemiology of SARS-CoV-2 indicates that most infections are likely spread through exposure to an infected individual at close range, within about 6 feet. However, recent reports indicate that aerosols remaining in the air over longer distances or times also have been involved in SARS-CoV-2 transmission in certain circumstances, often in poorly ventilated enclosed spaces and associated with behaviors such as singing, shouting, or breathing heavily during exercise. The Centers for Disease Control and Prevention (CDC) recently updated its guidance to acknowledge this potential for airborne spread of SARS-CoV-2.4

Blocking the dispersion of respiratory droplets from an individual infected with SARS-CoV-2 via use of a mask that functions as a physical barrier is a logical strategy to curb transmission. Surgical masks can reduce respiratory virus shedding in exhaled breath,5 and the filtering efficacy of some materials used in cloth masks may approach that of surgical masks.6

Respiratory droplets are produced not only by coughing and sneezing, but also when speaking and simply breathing.4 Light-scattering experiments indicate that 1 minute of loud speaking potentially can generate more than 1000 virion-containing aerosols that may linger in the air in a closed, stagnant environment.7 These particles may accumulate in enclosed spaces with poor ventilation, especially when individuals are singing, shouting, or breathing heavily (eg, with physical exercise). Therefore, the commonly observed practice of individuals removing their mask when speaking is not advisable. With the onset of colder weather in the northern hemisphere, activities will increasingly occur inside, resulting in often-unavoidable congregating. Therefore, it is particularly important to continually emphasize the necessity of consistent wearing of masks, particularly in the indoor setting.

Recent evidence suggests that up to 40% to 45% of people infected with SARS-CoV-2 may never be symptomatic but still can transmit the virus.4 Viral spread from people without symptoms may account for more than 50% of transmission events in COVID-19 outbreaks.8 Since it has now become evident that individuals capable of transmitting SARS-CoV-2 cannot be identified solely by the presence of symptoms, universal mask wearing in the community for source control is recommended.4

Masks should be used in combination with other modalities to prevent the spread of SARS-CoV-2, including physical distancing, hand hygiene, adequate ventilation, and avoiding crowded spaces. Widespread testing for SARS-CoV-2 infection is also important but insufficient on its own for pandemic control. No test is perfect; all have a lower limit of detection for viral material and the potential for false negatives. In addition, the result of a test represents just one point in time and does not indicate an individual’s status outside of the moment the specimen was collected. Testing, along with contact tracing and the isolation of individuals who are infected, is a key tool for curbing the spread of SARS-CoV-2. However, reliance on testing alone to prevent transmission will be ineffective without the use of additional strategies such as mask wearing and physical distancing.

As countries around the world seek to safely reopen businesses, schools, and other facets of society, mask use in the community to prevent the spread of SARS-CoV-2, in conjunction with other low-cost, low-tech, commonsense public health practices, is and will remain critical. Return to normalcy will require the widespread acceptance and adoption of mask wearing and other inexpensive and effective interventions as part of the COVID-19 prevention toolbox.

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Article Information

Corresponding Author: Andrea M. Lerner, MD, MS, National Institutes of Health, 31 Center Dr, Room 7A10A, Bethesda, MD 20892 (andrea.lerner@nih.gov).

Published Online: October 26, 2020. doi:10.1001/jama.2020.21946

Conflict of Interest Disclosures: None reported.

Lyu  W, Wehby  GL.  Community use of face masks and COVID-19: evidence from a natural experiment of state mandates in the US.   Health Aff (Millwood). 2020;39(8):1419-1425. doi:10.1377/hlthaff.2020.00818 PubMedGoogle ScholarCrossref
Wang  Y, Tian  H, Zhang  L,  et al.  Reduction of secondary transmission of SARS-CoV-2 in households by face mask use, disinfection and social distancing: a cohort study in Beijing, China.   BMJ Glob Health. 2020;5(5):e002794. doi:10.1136/bmjgh-2020-002794 PubMedGoogle Scholar
Wang  X, Ferro  EG, Zhou  G, Hashimoto  D, Bhatt  DL.  Association between universal masking in a health care system and SARS-CoV-2 positivity among health care workers.   JAMA. 2020;324(7):703-704. doi:10.1001/jama.2020.12897 PubMedGoogle ScholarCrossref
Centers for Disease Control and Prevention, Division of Viral Diseases, National Center for Immunization and Respiratory Diseases. Scientific Brief: SARS-CoV-2 and potential airborne transmission. Updated October 5, 2020. Accessed October 8, 2020. https://www.cdc.gov/coronavirus/2019-ncov/more/scientific-brief-sars-cov-2.html
Leung  NHL, Chu  DKW, Shiu  EYC,  et al.  Respiratory virus shedding in exhaled breath and efficacy of face masks.   Nat Med. 2020;26(5):676-680. doi:10.1038/s41591-020-0843-2 PubMedGoogle ScholarCrossref
Konda  A, Prakash  A, Moss  GA, Schmoldt  M, Grant  GD, Guha  S.  Aerosol filtration efficiency of common fabrics used in respiratory cloth masks.   ACS Nano. 2020;14(5):6339-6347. doi:10.1021/acsnano.0c03252 PubMedGoogle ScholarCrossref
Stadnytskyi  V, Bax  CE, Bax  A, Anfinrud  P.  The airborne lifetime of small speech droplets and their potential importance in SARS-CoV-2 transmission.   Proc Natl Acad Sci U S A. 2020;117(22):11875-11877. doi:10.1073/pnas.2006874117 PubMedGoogle ScholarCrossref
Moghadas  SM, Fitzpatrick  MC, Sah  P,  et al.  The implications of silent transmission for the control of COVID-19 outbreaks.   Proc Natl Acad Sci U S A. 2020;117(30):17513-17515. doi:10.1073/pnas.2008373117 PubMedGoogle ScholarCrossref
7 Comments for this article
Face masks
S Hasanain, M.D. | Cardiologist, Gottlieb Memorial Hospital
I wish this article and face masking advice by Dr. Fauci appeared in February or March, before we had over 8.9 million cases and 230,000 deaths, not to mention many trillions in financial losses. 
How We Know Masks Work
Russell Fitton, DDS | Private Practice
The best evidence that masks work doesn't come from theoretical papers or assumptions based on observation. Masks work because dentistry has been using masks since about 1986. Dentists have worn them through HIV, all the hepatitis outbreaks, SARS, H1N1,etc. There has never been an outbreak of any of the above in a dental office setting even with all the aerosols generated from dental handpieces and oral ultrasonic cleaning instruments. If you want people to understand that masks work just tell them to ask their dentist. It's interesting also that the infection rate for Covid-19 for dentists is less than 1%. 
Additional Low Tech Interventions
Dr Mubarak M Khan, MBBS, DLO, DNB (ENT) | Sushrut ENT Hospital & Dr Khan’s Research centre, Talegaön Dabhade, Pune, India
We are practising the following additional simple things in our daily routine in an office-based otolaryngology practice in the last 6 months:

1. P = PPE: creating a barrier between workers and the virus and other airborne diseases  (mask, gown, gloves, cap & faceshields, sanitizers)

2. U = UVc: Ultra Violet C germicidal light or Chemical disinfection of Environmental air s to reduce viral load. This must be specifically utilised for all OPD, Hospitals, Operation Theatres (OTs), all crowded places

3. B = Betadine: 0.5% povidone iodine gargles and nose drops for all patients before examination and
all health care workers who are busy treating patients irrespective of Covid status. 

4. V = Ventilation: Reverse ventilation filters (Exhaust Fan Filters) for air purification in hospitals, wards, ICU, OT. We have developed simple air filters from exhaust fans and surgical mask material and use them in our Opd wards and OTs. The same highly economical exhaust filter can be used in crowded areas and small homes (cost required to modify existing exhaust fan will be only $25 to $30). And similar high end exhaust filters can be used in high crowded places (like malls, local trains, hotels, restaurants, multiplexes)

Stay Safe .... Stay Healthy

Sincere regards

Dr Mubarak Muhamed Khan
Dr Sapna Ramkrishna Parab
Consultant & Directors

Sushrut ENT Hospital & Dr Khan’s Research centre, Talegaön Dabhade, Pune, India

1. Repurposing 0.5% povidone iodine solution in otorhinolaryngology practice in Covid 19 pandemic.
Khan, Mubarak Muhamed; Parab, Sapna Ramkrishna; Paranjape, Mandar.
Am J Otolaryngol ; 41(5): 102618, 2020.
Article in English | MEDLINE | ID: mdl-32574894
2. 0.5% povidone iodine irrigation in otorhinolaryngology surgical practice during COVID 19 pandemic.
Khan, Mubarak Muhamed; Parab, Sapna Ramkrishna.
Am J Otolaryngol ; 41(6): 102687, 2020 Aug 19.
Article in English | MEDLINE | ID: covidwho-720408
3. CIE (2003) CIE 155:2003 Ultraviolet Air Disinfection. Freely available at http://cie.co.at/news/cie-releases-two-key-publications-uv-disinfection2
4. Welch, D., Buonanno, M., Grilj, V., Shuryak, I., Crickmore, C., Bigelow, A.W., Randers- Pehrson, G., Johnson, G.W. and Brenner, D.J. (2018) Far-UVC light: A new tool to control the spread of airborne-mediated microbial diseases. Scientific Reports 8(1): 2752.
DOI: 10.1038/s41598-018-21058-w
5. CIE Position Statement on Ultraviolet (UV) Radiation to Manage the Risk of COVID-19 Transmission
May 12, 2020
Evidence is Clear and We Can Prevent Other Respiratory Infections
Erand Llanaj, MPH, MSc, PhD | Department of Public Health and Epidemiology, Faculty of Medicine, Uiversity of Debrecen
Lerner, Folkers, and Fauci outline the evidence and arguments for the utility of universal masking in these times that alternative effective solutions are scarce. We know what to do and we need to get the message out there to fight the rapid 'infection' of misinformation. Face coverings are saving lives during the coronavirus pandemic, but debate trundles on. An important piece of the argument to be considered is that on a population level masks prevent a lot of unnecessary suffering and deaths from COVID-19. Compliments to the authors for having the courage to advance this narrative.
Konda Filtration Efficacy Data
James Radney, Ph.D. Chemistry | NIST
There is an important caveat about this Viewpoint's reference 6 (1) that this viewpoint has failed to acknowledge. The authors of the Konda study drew the conclusion that  "hybrid masks offer slightly inferior [efficacy] to the N95 mask above 300 nm, but superior for particles smaller than 300 nm,” not that “the filtering efficacy of some materials used in cloth masks may approach that of surgical masks” as suggested in this Viewpoint.

The original and quite remarkable conclusions of the Konda manuscript could not be replicated in similar subsequent studies [e.g. 2, 3] as the experiments were conducted
at conditions well below physiologically relevant causing their measured filtration efficacies to disagree with those of the larger community. As a result, the authors have issued a correction to the original manuscript (4).

This correction has also been accompanied by multiple letters to the editor concerning their results [5-7]. As noted by Rule [6],

“Given these problems with the experimental design, we believe that the authors’ conclusions can lead the public to overestimate the protection these fabric masks can truly offer. As of this writing on June 30, 2020, the article has been viewed over 350,000 times. We encourage readers to consider the broader literature in which sound aerosol science has shown lower filtration efficiencies for fabric materials”.

This also highlights the need for the community to follow established protocols (e.g. Parts 3 and 5 of EN 1822 or ISO 29463) when assessing the effectiveness of materials in cloth face coverings. Regardless, the truth remains that the wearing a cloth face covering is an effective means of source control for slowing the transmission of COVID-19.


[1] Konda  A, Prakash  A, Moss  GA, Schmoldt  M, Grant  GD, Guha  S.  Aerosol filtration efficiency of common fabrics used in respiratory cloth masks.   ACS Nano. 2020;14(5):6339-6347. doi:10.1021/acsnano.0c03252
[2] Zangmeister, C. D.; Radney, J. G.; Vicenzi, E. P.; Weaver, J. L., Filtration efficiencies of nanoscale aerosol by cloth mask materials used to slow the spread of sars-cov-2. ACS Nano 2020, 14, 9188 - 9200.
[3] Drewnick, F.; Pikmann, J.; Fachinger, F.; Moormann, L.; Sprang, F.; Borrmann, S., Aerosol filtration efficiency of household materials for homemade face masks: Influence of material properties, particle size, particle electrical charge, face velocity, and leaks. Aerosol Sci. Technol. 2020, 1-17.
[4] Konda, A.; Prakash, A.; Moss, G.; Schmoldt, M.; Grant, G.; Guha, S., Correction to aerosol filtration efficiency of common fabrics used in respiratory cloth masks. ACS Nano 2020, 14, 10742 - 10743. 
[5] Carr, I. A.; Hariharan, P.; Guha, S., Letter to the editor regarding aerosol filtration efficiency of common fabrics used in respiratory cloth masks. ACS Nano 2020, 14, 10754-10755.
[6] Rule, A.; Ramachandran, G.; Koehler, K., Comment on aerosol filtration efficiency of common fabrics used in respiratory cloth masks: Questioning their findings. ACS Nano 2020, 14, 10756-10757.
[7] Hancock, J. N.; Plumley, M. J.; Schilling, K.; Sheets, D.; Wilen, L., Comment on “aerosol filtration efficiency of common fabrics used in respiratory cloth masks”. ACS Nano 2020, 14, 10758-10763.
National Mask Mandate and Lockdown
Hunasikatti Mahadevappa, MD, FCCP | Fairfax Hospital, Falls Church, VA 22042
The authors state that ' The implementation of mandates averted more than 200 000 cases of COVID-19 by May 22, 2020, according to modeling estimates". When there is so much data regarding the effectiveness of measures like mask-wearing, it is somewhat surprising why the COVID-19 Task Force did not recommend a national mandate. This is the only effective solution which should have been in the guidelines-even if this is opposed by the political establishment. At least medical experts would have done their job with clarity and directive to avoid deaths.

We have to learn from the success stories of
China and Europe. China's approach to the coronavirus is characterized by the initial draconian, 76-day lockdown seen in Wuhan, the central Chinese city where cases of the virus were first detected late last year. China's success in controlling the coronavirus is not so much a product of those early control measures -- though these have been utilized effectively to halt regional flare-ups -- but how the country handles things after people are allowed to move around again. In particular, China's ability to track, contact trace cases across the country whenever there is the suggestion of a new cluster of infections has enabled the government to respond quickly and bring local epidemics under control.

These are extraordinary times and we are in a medical emergency. We should declare an emergency and do what is necessary to control the pandemic. South Korea is a Democratic country . In SK, if people do not wear masks on public transportation and at demonstrations, as well as medical and care facilities, they will face a fine of up to 100,000 won ($87). Operators of those facilities and rally organizers will be fined up to 3M won for failing to ensure that users or participants comply with the requirement. 

All public health issues must remain bipartisan issues. No politician should be able to override the collective guidelines issues by CDC in consultation with other agencies. It is time to appoint chairpersons of public health agencies so they can function independently with no fear of reprisal from any one.

The US used to be a leader in epidemiological interventions and the whole world used to follow CDC guidelines. Today we are looking at countries like China, South Korea and Germany for their method of pandemic control. This can only be reversed if both parties decide that it is in the best interest of the nation , not to interfere with clinical decisions regarding public health formulated by the federal agencies
( These are my personal views and do not represent the policies of any organization)
Pharyngeal Antisepsis
Bruce Davidson, MD MPH | Providence Health Services, Seattle WA
Several common, very inexpensive, proven-safe mouthwashes (e.g., Listerine Ultra, $0.15/dose) are also shown (1, 2) to rapidly inactivate SARS-CoV-2 by > 4 logs (e.g., 50,000 to <5 viruses) with 60 seconds exposure. Gargling and swishing an effective antiseptic mouthwash for 60 seconds is shown (3) to reduce culture-positivity 5 minutes later of pharyngeal pathogen Neisseria gonorrhea (by >50%) compared to saline (p=0.013). Healthy adults don't aspirate while awake but are repeatedly proven to do so during sleep (4,5).

Preclinical evidence is repeated and robust. Clinical trials are not needed when the intervention has an indisputable safety record, consumes trivial
resources ($0.15 and 60 seconds before sleeping), and there is no time to confirm efficacy. This is why the 9 different US-available injected influenza vaccines with different and some new viral proteins have not been tested in clinical trials. Surveillance estimates efficacy post-hoc, as it will with this year's flu vaccines and would with pharyngeal antisepsis before sleep.

Why not try to persuade the public to participate to reduce SARS-CoV-2 prevalence where we dwell?

1. Meister TL et al, J Infect Dis, 2020 Sep 14;222(8):1289-1292. doi: 10.1093/infdis/jiaa471.
2. Meyers C et al, J Med Virol 2020:1-8. https://doi.org/10.1002/jmv.26514
3. Chow EPF, et al. Sex Transm Infect 2017;93:88–93.
4. Huxley EJ et al, Am J Med 1978;64:564-8
5. Gleeson K et al, CHEST 1997;111:1266-72