The effectiveness of different types of face masks

The Novel Coronavirus (COVID-19) continues to be a major health burden in many countries around the world with astonishing reports of fatalities. The burden on the health care systems around the world has been tremendous with a death toll of over 190,000 deaths in the US [1]. According to the World Health Organization (WHO), the Sars-CoV-2 virus that causes COVID-19 disease is spread via respiratory droplets [2]. According to a study published by Durgesh Sinha and Nicholas Klahn, from Tempa University and Rowan College at Burlington college respectively, on April 12th, 2020, titled “Mathematical modeling study of the 2020 Covid-19 outbreak in the United States”, 40% 80% of Covid-19 transmission arise from people who are pre-symptomatic or asymptomatic [3].


Introduction
The Novel Coronavirus (COVID-19) continues to be a major health burden in many countries around the world with astonishing reports of fatalities. The burden on the health care systems around the world has been tremendous with a death toll of over 190,000 deaths in the US [1]. According to the World Health Organization (WHO), the Sars-CoV-2 virus that causes COVID-19 disease is spread via respiratory droplets [2]. According to a study published by Durgesh Sinha and Nicholas Klahn, from Tempa University and Rowan College at Burlington college respectively, on April 12 th , 2020, titled "Mathematical modeling study of the 2020 Covid-19 outbreak in the United States", 40% -80% of Covid-19 transmission arise from people who are pre-symptomatic or asymptomatic [3].
In addition to social distancing and regular hand washing/ sanitizing techniques, WHO recommends that everyone above age 2 years old should wear a face mask to prevent further spread of the SARS-CoV-2 [4]. [5] Face masks are divided into two general categories; Medical and Non-medical. Medical face masks include professional respirators (N-95), surgical and non-surgical face masks. Non-medical face masks consist of homemade masks, and fi ltered masks.

Five (5) Factors that affect the effi cacy of face masks against SARS-CoV-2 ?
Size of respiratory droplets: It is important to note that SARS-CoV-2 viral particles are expelled from the respiratory tract as relatively large droplets whenever an infected individual talks, coughs, or sneezes, less so by simply breathing. Larger droplets fall to the ground while smaller droplets are generally suspended in the air then evaporate a few seconds later, downsizing to smaller droplets of about 5-10 micrometers that can fl oat longer in the air [6]. Therefore, for masks to be effi cacious, they must be able to fi lter particles of the aforementioned sizes. It is therefore important to consider the type of material used to make the face masks and what each is approved for fi ltering.

Mode of the expulsion of respiratory droplets:
Earlier studies suggested that the SARS-Cov-2 virus was spread mainly through coughing, but recent studies suggest that talking is also an important mode of transmission. The louder you speak, the more droplets are expelled and therefore there is a higher viral load transmission and an increased chance of transmitting the SARS-Cov-2 virus [6]. Coughing will force droplets into the air at more considerable force, allowing them to travel farther distances and widening the infectious perimeter around the infected party.

Material of face masks:
The Centers for Disease Control and Prevention National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA) regulate N95 respirators. They are tested for fl uid resistance, fi ltration effi ciency (particulate fi ltration effi ciency, and bacterial fi ltration effi ciency), fl ammability and biocompatibility [7]. Non-medical masks are made from different materials and designs with or without fi lter papers. The combination of material, amount of layers, the presence of fi lters and how tightly the material is woven will affect the effi cacy of the face mask [8].

Fit of face masks:
The fi t of the masks is very important to consider for protecting yourself against COVID-19. It should fi t tightly enough to create a seal but comfortably enough to prevent frequent repositioning. "In general, a mask is less helpful or counterproductive if it is not covering the nose and mouth, such as worn down around the neck for extended periods of time or if it is poorly fi tting to the point that it requires frequent adjustment, which brings your hands close to your face repeatedly," said Dr. George Anesi, director of the Medical Critical Care Bioresponse team at Penn Medicine [9].
The technique used in donning, removing and reusing face masks: WHO recommends extended use (up to 6 hours) over reuse but in extenuating circumstances, such as short supply, face masks can be re-processed (sterilized) and reused.
Extended use is accepted if the face mask is damaged, soiled, or wet [10]. The diagram below [ Figure 1] was recommended for guiding the reuse of face masks in the medical setting. For nonmedical settings, cloth masks should be washed frequently for the most effective outcome [8].

Effi cacy of Non-Medical face masks in preventing the spread of COVID-19
The use of non-medical face masks outside of the healthcare setting is recommended but may be inadequate in preventing the spread of the novel coronavirus says a study conducted by the College of Public Health Medicine Evidence-based COVID-19 Task Team. They stated that not much evidence has been garnered pertaining to the effi cacy of cloth masks in comparison to their medical counterparts. They also stated with moderate certainty that the number of cases increases with the use of cloth masks [11].
Non-medical masks are readily available from many local sources and therefore impossible to adequately regulate, which seems to be a part of the problem. The goal of communitywide mask-wearing is to quell the spread of the COVID-19 by decreasing the number of respiratory droplets that are spread by pre-symptomatic and asymptomatic carriers [12], says the European Center for Disease Control.
The percentage effi cacy of some household non-medical masks has been stated by one preprints article to be "between a 49% and 86% fi ltration rate for 0.02 μm exhaled particles whereas surgical masks fi ltered 89% of those particles." Additionally, they mentioned a laboratory testing which showed "household materials had 3% to 60% fi ltration rate for particles in the relevant size range, fi nding them comparable to some surgical masks" [6]. Ultimately, WHO recommends the use of tightly-woven fabric masks made of linen or cotton consisting of three or more layers. Additional worldwide recommendations include frequent mask washing, comfortable fi t, and proper removal techniques [13].
While the fi ght continues to quantify the benefi t of nonmedical masks, a few setbacks still remain. Many versions of non-medical masks provide an inadequate seal to the mouth and nose, there is poor fl uid resistance and frequent readjustment is required [14]. Poor compliance and misinformation about their effi cacy are also contributing factors. Regardless of these factors, they are effective in reducing the number of droplets spread when compared to the use of no mask at all [15].
Effi cacy of medical masks in preventing the spread of COVID-19 Table 1 A review in the International Journal of Nursing Studies [titled 'A rapid systematic review of the effi cacy of face masks and respirators against coronavirus and other respiratory transmissible viruses for the community], health care workers and sick patients' found that there is benefi t in using face mask for healthcare workers and community members. The article stated that ''In the community, masks seemed to be effective with and without hand hygiene and both together are protective." It also stated that continued use of face masks and respirators by health care workers throughout their entire shift had protective benefi ts against contracting and spreading the virus. [19,20]. Due to their scarce supply, WHO suggests that professional respirators should only be reserved for healthcare workers in direct contact with COVID-19 patients and procedural or surgical face masks can be worn by healthcare workers, not in direct contact with COVID-19 patients [4].

Effi cacy of medical masks against COVID-19 compared to that of non-medical face masks
The results from a comparison of surgical and homemade masks against bacterial and viral aerosols from the review article in the International Journal of Nursing mentioned above showed that "the median fi t factor of homemade masks was one half that of surgical masks. It went on to say that both surgical and homemade masks decreased the number of microorganisms expelled by the test subjects but the surgical masks were 3 times more effective [19,20].

Surgical Masks Respirators (N95, FFP) Cloths Masks
Testing and Approval [16] Classifi ed by ASTM Evaluated and certifi ed by NIOSH Have not been evaluated or tested to recognized standards .
Purpose -Also known as FRSM. -Provide a barrier to splashes and large droplets impacting the wearer's mouth, nose, and respiratory tract [17]. -Do not protect against smaller droplets.
-Can fi lter out both large and small particles when the wearer inhales [17].
-Sewn and non-sewn types -Intended to trap droplets that are released when the wearer talks, coughs, or sneezes.

Conclusion
Based on the literature reviewed, it is safe to say that wearing face masks at the community level and in medical settings will decrease the spread of COVID-19 by: 1. Preventing Sars-CoV-2 droplets from leaving the infected wearer and entering the environment.
2. Preventing Sars-CoV-2 droplets from entering the respiratory tract of the uninfected wearer .
Face masks can be used as personal protective equipment (PPE) or for blocking infected droplets produced by the wearer.
Some face masks can act as both PPE and a means of preventing droplet transmission from the wearer (Surgical Masks, N95) while others will only act as a PPE (N95 with one-way outlet valves) and do not protect the public from the wearer.
Others, such as the cloth mask will protect the public from the infected wearer but offer less protection for the wearer from the infectious public.
In summation, after a thorough review of 20 literatures, we have determined that the use of face masks will greatly reduce the spread of the SARS-CoV-2 virus at the community level and in medical settings, by reducing viral droplets transmission.