Face Mask Usage and Effectiveness

Abstract

Various types of face masks available to the general public are worn for protection against inhalation of dust, pollutants, allergens, and pathogenic organisms. Recent news stories have illustrated the widespread use of face masks for protection against Swine flu (H1N1), Severe Acute Respiratory Distress Syndrome (SARS), Highly Pathogenic Avian Influenza (HPAI) virus outbreaks in Asia, and dust from the collapse of the World Trade Cen- ter. However, the level of protection provided by face masks is unknown. The objective of this study was to determine how efficiently face masks prevent respiratory exposure to potentially harmful aerosols. Three types of commonly available face masks were tested: a surgical mask, a pre-shaped dust mask, and a bandana. An N95 respirator was tested as the positive control. 

…with a mass median aerodynamic particle size of 1.6 m. Face mask protective efficiency was calculated as the ratio of mannequin sample probe concentration to reference sample probe concentration. The protective efficiencies were 33.3%, 11.3%, and 6.1% for the surgical, bandana, and dust masks, respectively. The N95 mask protective efficiency was 89.6%. In conclusion, the surgical mask protected the best of the three face masks tested. However, it is important to note that all three masks offer very little protection when compared to the N95, and wearing these face masks may produce a false sense of protection.

Conclusions

Three commonly available face masks—a surgical mask, a pre-shaped mask, and a bandana—were challenged with saline aerosols in concentrations and particle size distributions representing dust storm conditions to determine their protective efficiencies. A N95 respirator was used as the positive control and challenged un- der the same conditions. All three masks performed poorly, with protective efficiencies less than 34% as compared to the N95 respirator that had a protective efficiency of nearly 90%. Possible factors related to the protective efficiencies observed with face masks and the N95 respirator includes the penetration efficiency and particle load characteristics of the fabrication materials. Equally important is the fit of the face mask and respirator. This may account for the less than 95% efficiency observed for the N95.

Protection from dust, allergens, and infectious aerosols with face masks and respirators is dependent on the aerosol concentration of the compound and the infectious or inhaled dose. The results demonstrate that use of these types of face masks may not provide as much protection as desired against inhaled aerosols.

Mask Benefits and Risks

Benefits and advantages

1) May reduce viral spread from viral shedders. This might be particularly important in the context of asymptomatic and pre-symptomatic people

2) Masks may provide protection in closed spaces, such as public transport

a. Considers protection by face masks against influenza A(H1N1)pdm09 virus on trans-pacific passenger aircraft, in 2009. “Wearing a face mask was a protective factor against influenza infection. We recommend a more comprehensive intervention study to accurately estimate this effect.”

3) Masks may provide some protection at mass gatheringsa. The paper concludes “A modest proportion of attendees of MGs [mass gatherings] use facemask, the practice is more widespread among health care workers. Facemask use seems to be beneficial against certain respiratory infections at MGs but its effectiveness against specific infection remains unproven.”

4) Masks can be effective when used alongside hand hygiene

a) Objective: “To investigate whether hand hygiene and use of facemasks prevents household transmission of influenza.”

b) Conclusion: “Hand hygiene and facemasks seemed to prevent household transmission of influenza virus when implemented within 36 hours of index patient symptom onset. These findings suggest that nonpharmaceutical interventions are important for mitigation of pandemic and interpandemic influenza.”

c) Importantly: “Adherence to interventions varied.”

5) Cloth masks can be made at home at low cost washable and reusable and therefore reduce the demand on the ones needed by healthcare professionals

6) Universal wearing of masks fosters a sense of social solidarity in response to the pandemic

7) Masks were a potential link to lower risk of SARS amongst people without known contact during the SARS epidemic

8) Medical masks and N95 masks can be reused for a few days with steam decontamination between use.

Risks and pitfalls

1. Masks are not as effective hand-washing

2. Not as effective as social distancing.

3. N95 masks are most effective, followed by surgical masks. Homemade masks are least effective

4. Used/dirty masks not disposed of correctly become a health hazard

5. Difficult to use for some people to use, such as young children or people with respiratory issues

6. Self-contamination by touching and reusing contaminated mask

7. Cloth (homemade) masks can become a breeding ground for pathogens due to irregular washing, moisture retention, and poor filtration

8. May be used instead of, rather than as well as, hand-washing and social distancing

9. Mandatory wearing increases demand, stretches supply - particularly for those required by health professionals

10. Masks must fit correctly to be effective

11. Masks must be used correctly to be effective

12. Researchers have found that masks may not be as effective at filtering COVID-19

13. Masks can instil a false sense of security which could lead to engaging in higher risk behaviours

14. Low compliance for mask wearing in uninfected close contacts

15. Masks could create a false sense of security that could end up putting people at greater risk. Even with the mouth and nose fully covered, the virus can still enter through the eyes.

16. Depending on type of mask used, potential breathing difficulties

17. Masks associated with increased face-touching

18. Improper decontamination of medical masks or N95 masks can damage the blocking structure of masks

Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1

April 16, 2020
N Engl J Med 2020; 382:1564-1567
DOI: 10.1056/NEJMc2004973
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TO THE EDITOR:

A novel human coronavirus that is now named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (formerly called HCoV-19) emerged in Wuhan, China, in late 2019 and is now causing a pandemic.1 We analyzed the aerosol and surface stability of SARS-CoV-2 and compared it with SARS-CoV-1, the most closely related human coronavirus.2

We evaluated the stability of SARS-CoV-2 and SARS-CoV-1 in aerosols and on various surfaces and estimated their decay rates using a Bayesian regression model (see the Methods section in the Supplementary Appendix, available with the full text of this letter at NEJM.org). SARS-CoV-2 nCoV-WA1-2020 (MN985325.1) and SARS-CoV-1 Tor2 (AY274119.3) were the strains used. Aerosols (<5 μm) containing SARS-CoV-2 (105.25 50% tissue-culture infectious dose [TCID50] per milliliter) or SARS-CoV-1 (106.75-7.00 TCID50 per milliliter) were generated with the use of a three-jet Collison nebulizer and fed into a Goldberg drum to create an aerosolized environment. The inoculum resulted in cycle-threshold values between 20 and 22, similar to those observed in samples obtained from the upper and lower respiratory tract in humans.

Our data consisted of 10 experimental conditions involving two viruses (SARS-CoV-2 and SARS-CoV-1) in five environmental conditions (aerosols, plastic, stainless steel, copper, and cardboard). All experimental measurements are reported as means across three replicates.

Figure 1. Viability of SARS-CoV-1 and SARS-CoV-2 in Aerosols and on Various Surfaces.

SARS-CoV-2 remained viable in aerosols throughout the duration of our experiment (3 hours), with a reduction in infectious titer from 103.5 to 102.7 TCID50 per liter of air. This reduction was similar to that observed with SARS-CoV-1, from 104.3 to 103.5 TCID50 per milliliter (Figure 1A).

SARS-CoV-2 was more stable on plastic and stainless steel than on copper and cardboard, and viable virus was detected up to 72 hours after application to these surfaces (Figure 1A), although the virus titer was greatly reduced (from 103.7 to 100.6 TCID50 per milliliter of medium after 72 hours on plastic and from 103.7 to 100.6TCID50 per milliliter after 48 hours on stainless steel). The stability kinetics of SARS-CoV-1 were similar (from 103.4 to 100.7 TCID50 per milliliter after 72 hours on plastic and from 103.6 to 100.6TCID50 per milliliter after 48 hours on stainless steel). On copper, no viable SARS-CoV-2 was measured after 4 hours and no viable SARS-CoV-1 was measured after 8 hours. On cardboard, no viable SARS-CoV-2 was measured after 24 hours and no viable SARS-CoV-1 was measured after 8 hours (Figure 1A).

Both viruses had an exponential decay in virus titer across all experimental conditions, as indicated by a linear decrease in the log10TCID50per liter of air or milliliter of medium over time (Figure 1B). The half-lives of SARS-CoV-2 and SARS-CoV-1 were similar in aerosols, with median estimates of approximately 1.1 to 1.2 hours and 95% credible intervals of 0.64 to 2.64 for SARS-CoV-2 and 0.78 to 2.43 for SARS-CoV-1 (Figure 1C, and Table S1 in the Supplementary Appendix). The half-lives of the two viruses were also similar on copper. On cardboard, the half-life of SARS-CoV-2 was longer than that of SARS-CoV-1. The longest viability of both viruses was on stainless steel and plastic; the estimated median half-life of SARS-CoV-2 was approximately 5.6 hours on stainless steel and 6.8 hours on plastic (Figure 1C). Estimated differences in the half-lives of the two viruses were small except for those on cardboard (Figure 1C). Individual replicate data were noticeably “noisier” (i.e., there was more variation in the experiment, resulting in a larger standard error) for cardboard than for other surfaces (Fig. S1 through S5), so we advise caution in interpreting this result.

We found that the stability of SARS-CoV-2 was similar to that of SARS-CoV-1 under the experimental circumstances tested. This indicates that differences in the epidemiologic characteristics of these viruses probably arise from other factors, including high viral loads in the upper respiratory tract and the potential for persons infected with SARS-CoV-2 to shed and transmit the virus while asymptomatic.3,4 Our results indicate that aerosol and fomite transmission of SARS-CoV-2 is plausible, since the virus can remain viable and infectious in aerosols for hours and on surfaces up to days (depending on the inoculum shed). These findings echo those with SARS-CoV-1, in which these forms of transmission were associated with nosocomial spread and super-spreading events,5and they provide information for pandemic mitigation efforts.

Six Degrees of Kevin Bacon

Six Degrees of Kevin Bacon or "Bacon's Law" is a parlour game based on the "six degrees of separation" concept, which posits that any two people on Earth are six or fewer acquaintance links apart. Movie buffs challenge each other to find the shortest path between an arbitrary actor and prolific actor Kevin Bacon. It rests on the assumption that anyone involved in the Hollywood film industry can be linked through their film roles to Bacon within six steps. In 2007, Bacon started a charitable organization called SixDegrees.org.

COVID-19 Symptoms

Watch for symptoms

Reported illnesses have ranged from mild symptoms to severe illness and death for confirmed coronavirus disease 2019 (COVID-19) cases.

The following symptoms may appear 2-14 days after exposure.*

• Fever

• Cough (typically dry)

• Shortness of breath

80% of COVID-19 patients experience 'mild' symptoms — but that likely still involves a fever and cough

• Eighty percent of COVID-19 cases are considered mild.

• But nearly 99% of COVID-19 patients experience the same symptoms — fever, dry cough, and fatigue — at different levels of severity.

The fever is usually the first symptom to arrive, according to the research. An increase in body temperature is a sign the immune system is fighting an infection.

Bacteria and viruses survive well in normal body temperatures of about 98.7 degrees Fahrenheit, so a mild fever of about 100.4 degrees (and a more severe fever of 103 degrees) is a way to fight off pathogens.

https://www.businessinsider.com/what-coronavirus-mild-symptoms-are-fever-2020-3