By Colleen Maher, OMS-IV, Rocky Vista University College of Osteopathic Medicine
2021 Namey/Burnett Preventive Medicine Writing Award Winner, Second Place

Sponsored by the ACOFP Education and Research Foundation, with winners selected by the ACOFP Health & Wellness Committee, the Namey/Burnett Preventive Medicine Writing Award honors the memory of Joseph J. Namey, DO, FACOFP, and John H. Burnett, DO, FACOFP—dedicated advocates for osteopathic medicine—and recognizes the best preventive medicine blog posts submitted by osteopathic family medicine students, interns and residents.

In the day and age of the coronavirus disease (COVID-19) pandemic, many are searching for consistent guidance on measures they can take to protect themselves and loved ones. Primary care physicians are often on the front lines of these conversations and, as such, it is vital that a uniform, evidence-based message is being relayed to patients on up-to-date recommendations.

Current numbers as of the submission of this piece put cases at 72.7 million with over 1.6 million deaths worldwide.1 In the midst of the holiday season, with many suffering from what is being termed “pandemic fatigue,” there is a very distinct possibility that these numbers will increase exponentially. While assistance from a vaccine appears to be on the horizon, it is vital that healthcare professionals continue to encourage behaviors that help to slow the rate of transmission. The goal of this literature review is to explore the historical development of the face mask as well as current research on the role of this preventative measure in the COVID-19 pandemic.

The evolution of the face mask in the medical field

Face coverings in their earliest form were coverings for the nose and mouth directed towards protecting from the “blight, the miasma, which was considered the cause of the plague” during the epidemic of the Middle ages.2 The field of surgery was one of the first to adopt aseptic practices in an effort to prevent wound infections which limited the effectiveness of many procedures.

In response to experiments demonstrating both germ theory, as well as the infectious nature of respiratory droplets, multiple surgeons including Johann Mikulicz in what is now Poland and Paul Berger in Paris began wearing face masks in the operating room. This approach marked a transition in thinking away from trying to kill germs with chemicals towards a preventative “strategy of infection control that focused on keeping all germs away” in the first place. 3

There were several events that served as catalysts for face masks becoming a preventative measure to protect healthcare workers (HCWs) and patients alike from infectious diseases even in settings outside of the operating room. During the Manchurian plague epidemic of 1910, the Spanish influenza pandemic of 1918, and the Los Angeles pneumonic plague epidemic of 1924, materials including cotton and gauze were used in homemade face masks and infection rates among the HCWs wearing these masks were low.3,4

The value of the face mask as a protective tool continued to be validated as the world encountered new challenges during the 21st century. Studies from hospitals in Hong Kong during the 2003 SARS outbreak demonstrated that staff who used masks, gloves, gowns, and handwashing remained healthy. Of all of these preventative measures, mask wearing was determined to be the most significant and important measure taken.5

What is considered to be one of the foundational studies on face masks was a 2011 randomized control trial (RCT) in Hanoi, Vietnam. This RCT evaluated HCWs in “high-risk wards” which were defined as: emergency, infectious/respiratory disease, intensive care and pediatrics.6 There was random assignment to one of 3 groups: medical masks, cloth masks, or the control group defined as “standard practice, which may or may not include mask use.” 6

This study highlighted a common challenge in evaluating face mask efficacy in HCWs. Namely, the ethical dilemma in creating a true control group where subjects would be required to forgo any type of face covering for personal protection even in high-risk environments. Despite this challenge, the study provided valuable results indicating that the rate of infection in all outcome measures was significantly higher in the cloth mask group when compared to the medical mask group. Additionally, the filtration efficacy of the cloth masks was found to be very low with particle penetration of 97% as compared to 44% in medical masks.6

Although there are some limitations with these studies, the results consistently support that medical grade surgical masks and personal respirators are the most effective face coverings. These items should be reserved for HCWs and cloth face masks should be used as a last resort in these high-risk environments.

Face masks in the general population

As has become readily apparent in the face of our current global pandemic, it is not only HCWs who will be wearing face masks as preventative measures. While many studies underscore the importance of the protective effects of face masks in HCWs, they have poor generalizability to the population at large.

To address this deficiency in data, additional studies have used untrained adult and children volunteers as representatives of the general population. Using this study population helps to highlight the greater difference in “training level, goodness of fit and activities interfering with mask use”—all of which could reduce the protective effects of face masks. 7

Many of these studies evaluated two distinct forms of protection. Inward protection is the protection conferred by the wearer of the face mask. In the healthcare setting, this is the type of protection that healthy HCWs employ to protect themselves when caring for infectious patients. In contrast, outward protection is the protection face masks offer by retaining respiratory particles expelled by the wearer regardless of if they are actively symptomatic or not. This is the type of protection offered to those around the wearer. It is the principle employed by HCWs to protect patients in settings such as the sterile environment of the operating room or when caring for immunocompromised patients.

Foreseeing the coming H1N1 Influenza pandemic, a 2008 study was performed to compare the efficacy of personal respirators, surgical masks, and homemade face masks. Results indicated that the personal respirator provided 25 times the inward protection compared to surgical masks and 50 times the protection when compared to the homemade mask.7 Another study evaluated outward protection by identifying the number of microorganisms isolated after coughing with participants wearing no mask, a homemade mask, or a surgical mask. The results indicated that both masks (cloth and surgical) succeeded in reducing microorganism expulsion as compared to no mask. However, the surgical mask had 3 times the effectiveness in blocking transmission when compared to the homemade cotton mask, a difference that became even more apparent with particles that were smaller in size.8

While results consistently demonstrate distinct superiority in protection using personal respirators and surgical masks, they also highlight that homemade masks confer protection to the wearer and those around them when compared to no mask at all. Given this fact, authors of these studies argue that, in the setting of a pandemic, homemade face masks would prove incredibly valuable in reducing the transmission rate providing precious time for communities to cope with the crisis. As Chua et al. put it, “wearing a simple cloth mask is far better than wearing no mask to safeguard the wearer and the others’ health.”5

The homemade cloth face mask

Many studies predicted that in the setting of a global pandemic, a shortage of raw materials or transport restrictions might limit the availability of medical grade personal respirators and surgical masks. This has indeed come to fruition during the current COVID-19 pandemic. Given these limitations, masks made at home from readily available materials serve as valuable protection to the general population who are primarily exposed to lower-risk environments.

When looking at the construction of cloth face masks, it comes down to a balance between filtration efficacy and pressure drop. Pressure drop is a measure that determines the comfortability and breathability of the mask. Results from past data have determined that masks constructed from cotton T-shirts or pillowcase material provide the best filtration efficacy while still having a pressure drop that allows the mask to be worn comfortably. Materials such as the vacuum cleaner bag and tea towel demonstrated higher levels of filtration efficacy, but the measured pressure drops were too high for them to be worn comfortably for prolonged periods of time. 8

To provide the highest level of protection from a homemade cloth face mask, the CDC recommends a multilayered, water-resistant fabric with a high thread count and fine weave that uses behind the head ties (as opposed to ear loops) to help create a good seal to the face. 3 Given these recommendations, online sewing patterns and DIY face mask tutorials have recently gained in popularity.

One such model for the homemade cloth face mask was developed in early 2020 by a group of researchers from the American Chemical Society. Their method involves combining commonly available fabrics such as cotton-silk, cotton-chiffon, and cotton-flannel to help achieve filtration efficacy of >80% for particles <300 nm and >90% for particles >300nm.9 This high efficacy is a result of the synergistic effect of the mechanical filtration from the cotton fabric coupled with the electrostatic filtration of the second material as depicted below.9

Figure 1: Inward and outward protection conferred from the multilayer homemade cloth face mask as described by Konda et al.9 Figure was created by author, Colleen Maher, OMS-IV

As with most preventative medicine topics, education is imperative. Some key education topics that primary care physicians can help to impart on patients include proper mask construction as above, donning and doffing procedures, as well as cleaning of the mask. Helping patients to understand these items will assist in avoiding self-contamination behaviors and to help curb the false sense of protection that can accompany the wearing of a face mask.

Reusability is an important advantage that the cloth face mask has over medical grade masks and certain personal respirators which are designed for one-time use followed by proper disposal. While no specific guidelines exist for cleaning and decontamination of cloth masks, it is suggested that washing with soap and hot water should be adequate.4

A meta-analysis examined this unofficial recommendation and found that after four wash-dry cycles cloth masks had a 20% decrease in filtration efficacy.10 Additionally, when looking at the microscopic make-up of the masks, there was an “increase in pore size, change in pore shape, and decrease in number of microfibers in each pore” after each wash-dry cycle.10 This data highlights the importance of each individual having multiple cloth face masks available for use to allow for proper cleaning and rest time with the goal of maintaining the efficacy for as long as possible.

Prevention over politics

One of the challenges of the current pandemic is that at the onset, the scientific community was facing a completely new adversary. With the novelty of this virus as well as in an attempt to prevent hoarding and panic buying, there have been conflicting recommendations on face masks from public health organizations. For example, during early part of the pandemic in February 2020, the World Health Organization (WHO) published a report indicating that, “the proportion of truly asymptomatic carriers of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection was relatively small and was not a major driver of virus circulation.”11

However, as time has progressed, data from hard hit areas such as Northern Italy and China indicates that anywhere from 50–78% of laboratory confirmed positive cases were from individuals who were asymptomatic or presymptomatic.11 Even in areas that have experienced a smaller impact from the virus, studies suggest that at least 20–25% of positive cases will either be asymptomatic or have very mild symptoms.3

Additionally, it was initially believed that droplet transmission via contaminated fomites was the major route of transmission of the SARS-CoV-2 virus.11 Airborne transmission was thought to occur only when aerosol generating procedures such as intubation, bronchoscopy, and positive-pressure ventilation were performed.11

As further studies have been completed, more evidence has been obtained supporting the fact that the virus is indeed aerosolized and this can occur during regular daily activities such as breathing, talking, coughing, and sneezing.  Imaging using laser light scattering has demonstrated that masks can provide a physical barrier to respiratory droplets during these daily activities and prove most effective when worn by the person who is emitting the infectious particles.5

As this new data has become available, public health recommendations have adapted. Now both the WHO and CDC are recommending universal face masks for all individuals when in public places.12,13 It is important to highlight that in the current public health guidelines, universal means universal. Theoretical models including the SEIR (susceptible-exposed-infectious-recovered) performed during the early stages of the pandemic demonstrated that if 80% of the population wore a face mask this could flatten the curve more significantly than a strict lockdown. Yet when this number was decreased to 50% of the population, the face mask intervention failed and the curve remained exponential.5

While initially a theoretical model, this principle has been illustrated in reality as well. Hong Kong is a prime example of the importance of universal masking. While the Hong Kong government initially recommended that only symptomatic individuals wear masks per WHO guidelines, the general public voluntarily chose to wear face masks proactively. After 100 days, it was found that Hong Kong had a significantly lower number of infected per million compared to similar countries which is particularly exceptional given the high population density and proximity to China.5

Unlike Hong Kong, the response in the United States has been hindered by resistance to many public health measures including face mask requirements. As such, it is unsurprising that the number of cases and deaths in the US have been comparatively much higher. At a governmental level it is imperative that science is guiding the legislature regarding COVID-19 related policies, but regardless of those decisions’ HCWs must put all politics aside and advocate based on the data. When it comes to advising their patient panel, primary care physicians must work to continue to present a unified message that supports cloth face mask wearing in public places as a preventative measure to help keep the greatest number of people safe.

While there is certainly room and need for additional research on face masks, historical events and current data alike support their importance as prevention during pandemics. It is also evident that no one single approach will solve the current crisis. Given that strict lockdowns are unsustainable and economically devastating, it is vital that additional public health measures be encouraged.

Face masks are one of our best methods of prevention, but adjunctive measures—such as isolating positive cases, proper hand hygiene, immunization when it becomes readily available, and social distancing—are all vital as well. The public health measures taken now will, in part, determine the trajectory of devastation in this COVID-19 pandemic until a viable, global solution is put into place.


  1. Coronavirus resource center. John Hopkins Medicine & University. Updated 2020 Dec 13.  Accessed 2020 Dec 13.
  2. Matuschek C, Moll F, Fangerau H, et al. The history and value of face masks. Eur J Med Res. 2020;25(1):23. Published 2020 Jun 23. DOI:10.1186/s40001-020-00423-4
  3. Schilich T, Strasser B. A history of the medical mask and the rise of throwaway culture. The Art of Medicine. 2020;396(10243):19-20. Published 2020 May 22. DOI: 10.1016/S0140-6736(20)31207-1
  4. Chughtai AA, Seale H, Macintyre C. Effectiveness of Cloth Masks for Protection Against Severe Acute Respiratory Syndrome Coronavirus 2. Emerging Infectious Diseases. 2020;26(10):1-5. doi:10.3201/eid2610.200948.
  5. Chua MH, et al. Face Masks in the New COVID-19 Normal: Materials, Testing, and Perspectives. Research. Vol. 2020, Article ID  7286735, 40 pages. Published 2020 Apr 7.
  6. MacIntyre CR, Seale H, Dung TC, et al. A cluster randomised trial of cloth masks compared with medical masks in healthcare workers. BMJ Open. 2015;5(4):e006577. Published 2015 Apr 22. doi:10.1136/bmjopen-2014-006577
  7. van der Sande M, Teunis P, Sabel R. Professional and home-made face masks reduce exposure to respiratory infections among the general population. PLoS One. 2008;3(7):e2618. Published 2008 Jul 9. doi:10.1371/journal.pone.0002618
  8. Davies A, Thompson KA, Giri K, Kafatos G, Walker J, Bennett A. Testing the efficacy of homemade masks: would they protect in an influenza pandemic?. Disaster Med Public Health Prep. 2013;7(4):413-418. doi:10.1017/dmp.2013.43
  9. Konda A, Prakash A, Moss GA, Schmoldt M, Grant GD, and Guha S. Aerosol filtration efficiency of common fabrics used in respiratory cloth masks. ACS Nano. 2020; vol. 14 (no. 5): pp. 6339–6347. Published 2020 Apr 24.
  10. Jain M, Kim ST, Xu C, Li H, Rose G. Efficacy and Use of Cloth Masks: A Scoping Review. Cureus. 2020;12(9):e10423. Published 2020 Sep 13. doi:10.7759/cureus.10423
  11. Esposito S, Principi N, Leung CC, Migliori GB. Universal use of face masks for success against COVID-19: evidence and implications for prevention policies. Eur Respir J. 2020;55(6):2001260. Published 2020 Jun 18. doi:10.1183/13993003.01260-2020
  12. Coronavirus disease (COVID-19) advice for the public: When and how to use masks. World Health Organization. Updated 2020 Dec 1. Accessed 2020 Dec 13.
  13. COVID-19 (Coronavirus Disease) How to Protect Yourself & Others. Centers for Diseases Control and Prevention. Updated 2020 Nov 27. Accessed 2020 Dec 13.

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