Page 22 - Layout 1

COVID-19
PANDEMIC Use of Cloth Masks by the Public
continued from page 21

ginal protection by the homemade masks. Children (5-11 yrs) were of cloth masks in the general public nor do they refute the idea that
shown to have less inward protection from masks than adults but there is no protective value. None of the studies cited considered
there were no differences between men and women. The authors an environment with masks worn by both persons who were in-
concluded overall that any type of general mask use is likely to de- fected and persons wishing to avoid infection. Much also may de-
crease viral exposure and infection risk on a population level (van pend on the type of material and numbers of layers being worn as
der Sande, Teunis, and Sabel, 2008). a mask, the tightness of fit and the
A later study tested a variety of materials (e.g. tea towels, pil- user’s adherence to consistent
lowcase, cotton T-shirt, linen and silk) against surgical wear in risk situations and
masks for their ability to block transmission of cleaning before the next
micro-organisms when a person coughed. use. Perhaps enterprising
They concluded, unsurprisingly, that researchers are gathering
surgical masks were at least 3 good data from our current ex-
times more effective than any perience to better inform us in the fu-
of the other tested materi- ture.
als and that homemade However, I think two things are clear. The
masks, while not useless, first is that cloth mask use is inferior to social dis-
should only be consid- tancing as a means of preventing community spread,
ered a last resort. (Davies especially to the most vulnerable. The second is that
et al, 2013) healthcare workers deserve the quality of masks, either sur-
Concern for healthcare gical or N95, recommended for their level of care. We shouldn’t
workers in developing coun- lose sight of either.
tries who may only have cloth masks, prompted one large prospec-
tive randomized study of cloth masks vs. surgical masks while Dr Diane Simpson retired in late 2018 after over 30 years of work in public
providing medical care. Just over 1600 healthcare workers in wards health. Her career focused on the control of communicable diseases at the local,
within 15 hospitals in Hanoi, Viet Nam volunteered to participate. state and national levels. Dr. Simpson is a member of the Bexar County Med-
Depending on the ward, the staff wore cloth masks exclusively, sur- ical Society.
gical masks exclusively or either a cloth mask or surgical mask (i.e.
standard of care) while working their shifts. They were evaluated References
over a five-week period for development of influenza like illness or Davies, A, Thompson, K-A, Giri, K, kafatos, G, Walker, J, Bennett, A.
a laboratory confirmed respiratory viral illness. Surgical masks were (2013). Testing the Efficacy of Homemade Masks: Would They Protect in
a Pandemic? Disaster Medicine and Public Health Preparedness 7: (4) 413-
much more protective than cloth masks and provided better particle
418. DOI: 10.1017/dmp.2013.43
filtration. The authors concluded that cloth masks should not be
used by healthcare workers especially in high risk situations. (Mac- Konda, A, Prakash, A, Moss, G.A, Schmoldt, M, Grant, G.D, and Guha,
S. (2020). Aerosol Filtration Efficiency of Common Fabrics Used in Res-
Intyre et al, 2015)
piratory Cloth Masks ACS Nano 2020, Publication Date: April 24, 2020,
Not all cloth masks are created equal. A recent article published https://doi.org/10.1021/acsnano.0c03252. Copyright © 2020 American
on-line in ACS (American Chemical Society) NANO evaluated the Chemical Society
ability of several different materials and material hybrids to filter MacIntyre, C.R, Seale H, Dung, T.C, Hien, N.T, Nga, P.T, Chugtai, A.A,
particles ranging in size from 10 nanometers (nm) to 10 microns. Rahman, B, Dwyer, D.E, Wang, Q. (2015). A Cluster Randomised Trial of
The authors determined that the filtration efficiencies for a single Cloth Masks Compared with Medical Masks in Healthcare Workers. BMJ
layer of various fabrics ranged anywhere from 5 to 80% for particles Open 2015; 5:e006577. DOI:10.1136/bmjopen-2014-006577
<300nm and 5 to 95% for particle >300 nm. Filtration efficiencies Qualls, N, Levitt, A, Kanade, N, Wright-Jegede, N, Dopson, S, Bigger-
of multiple layers and specific combinations of fabrics such as cot- staff, M, Reed, C, Uzicanin, A. (2017). Community Mitigation Guidelines
to Prevent Pandemic Influenza — United States, 2017. Morbidity and Mor-
ton−silk, cotton−chiffon, and cotton−flannel were better with
tality Weekly Reort, Recommendations and Reports. 66(No. RR-1):1–34.
>80% filtration efficiency for particles <300 nm and >90% for par-
DOI: http://dx.doi.org/10.15585/mmwr.rr6601a1external icon.
ticles >300 nm. (Konda et al, 2020)
Rempfer, K. Army Times https://www.army times.com/news/your-
Another very recent evaluation by the US Army Combat Capa-
army/2020/04/24/army-researchers-say-this-is-the-best-material-for-a-
bilities Development Command looked at different fabrics for use homemade-face-mask-theyve-found-so-far/
in cloth face masks. This group found that the best, easy-to-find
Van der Sande, M, Teunis, P, Sabel, R. (2008). Professional and Home-
material to protect against coronavirus transmission is four-ply, mi-
made Face Masks Reduce Exposure to Respiratory Infections among the
crofiber cloth. This material, found in the cleaning section of most
General Population. Plos One 3(7) e2618.
big box stores, filters out more than 75 percent of particles 0.2-0.3 DOI:10.1371/journal.pone.0002618
microns in size. (Rempfer, 2020)
These studies neither provide overwhelming evidence in support
22 San Antonio Medicine • June 2020