Sit on the edge of your seat no longer.
Here are some sources to the extensive scientific literature that establishes that wearing masks is pointless in preventing viral spread:
Jacobs, J. L. et al. (2009) “Use of surgical face masks to reduce the incidence of the common cold among health care workers in Japan: A randomized controlled trial,” See: American Journal of Infection Control, Volume 37, Issue 5, 417 – 419.
https://www.ncbi.nlm...pubmed/19216002
It however only requires them wear the mask at work, and it is only a surgical mask which are not very effective. They could have easily contract the cold at home or the coffee shop. The sick patients in the hospital were not wearing masks, so the protection conferred was not both ways. We already know that is not very effective.
The number of layers used also helps stop the 0.3 micron tricky zone,
A single ply mask is likely less effective than a tight-fitting three layer fabric contraption.
Small particles zigzag due to Brownian motion, and are easily captured. Large particles get strained out, or have too much inertia to turn, and hit a fiber. Mid-size particles follow flowlines and are more likely to get through the filter; the hardest size to filter is 0.3 microns diameter.[12]
“N95-masked health-care workers (HCW) were significantly more likely to experience headaches. Face mask use in HCW was not demonstrated to provide benefit in terms of cold symptoms or getting colds.” See: Cowling, B. et al. (2010) “Face masks to prevent transmission of influenza virus: A systematic review,” Epidemiology and Infection, 138(4), 449-456.
https://www.cambridg...s-a-systematic- review/64D368496EBDE0AFCC6639CCC9D8BC05
Again, just suggesting they are not effective one-way but need to be worn both ways. Anyone watching cable news would have heard this peculiar fact coming from the media in March.
There is some evidence to support the wearing of masks or respirators during illness to protect others, and public health emphasis on mask wearing during illness may help to reduce influenza virus transmission. There are fewer data to support the use of masks or respirators to prevent becoming infected. Further studies in controlled settings and studies of natural infections in healthcare and community settings are required to better define the effectiveness of face masks and respirators in preventing influenza virus transmission.
"None of the studies reviewed showed a benefit from wearing a mask, in either HCW or community members in households (H). See summary Tables 1 and 2 therein. See: bin-Reza et al. (2012) “The use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence,” Influenza and Other Respiratory Viruses 6(4), 257–267.
https://onlinelibrar...59.2011.00307.x
Nothing but a critical review of the literature, which a paragraph after what you posted surmises this:
Some evidence suggests that mask use is best undertaken as part
of a package of personal protection especially hand hygiene. The
effectiveness of masks and respirators is likely linked to early,
consistent and correct usage.
“There were 17 eligible studies. None of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection.” See: Smith, J.D. et al. (2016) “Effectiveness of N95 respirators versus surgical masks in protecting health care workers from acute respiratory infection: a systematic review and meta-analysis,” CMAJ Mar 2016
https://www.cmaj.ca/content/188/8/567
Another dubious review with small sample size (N=6) and extremely wide confidence intervals [influenza-like illness (RCTs: OR 0.51, 95% CI 0.19–1.41)], which nevertheless again confirms the benefit of good, quality N95 masks 
Although N95 respirators appeared to have a protective advantage over surgical masks in laboratory settings, our meta-analysis showed that there were insufficient data to determine definitively whether N95 respirators are superior to surgical masks in protecting health care workers against transmissible acute respiratory infections in clinical settings.
“We identified six clinical studies. In the meta-analysis of the clinical studies, we found no significant difference between N95 respirators and surgical masks in associated risk of (a) laboratory-confirmed respiratory infection, (b) influenza-like illness, or © reported work-place absenteeism.” See: Offeddu, V. et al. (2017) “Effectiveness of Masks and Respirators Against Respiratory Infections in Healthcare Workers: A Systematic Review and Meta-Analysis,” Clinical Infectious Diseases, Volume 65, Issue 11, 1 December 2017, Pages 1934–1942,
https://academic.oup...11/1934/4068747
Nothing but a positive result, suggesting we wear masks lol.
This systematic review and meta-analysis supports the use of respiratory protection. However, the existing evidence is sparse and findings are inconsistent within and across studies.
“Self-reported assessment of clinical outcomes was prone to bias. Evidence of a protective effect of masks or respirators against verified respiratory infection (VRI) was not statistically significant”; as per Fig. 2c therein. See: Radonovich, L.J. et al. (2019) “N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial,” See: JAMA. 2019; 322(9): 824–833.
https://jamanetwork....article/2749214
Again no distinction is made between groups "always" and "sometimes" wearing their mask. Masks are the more effective the more often they are worn out. If a study is carelessly lumping together the most diligent with the most lackadaisical, it is lacking in scientific methodology.
So just not a very insightful meta-analysis in this case.
“Among 2862 randomized participants, 2371 completed the study and accounted for 5180 HCW-seasons. Among outpatient health care personnel, N95 respirators vs medical masks as worn by participants in this trial resulted in no significant difference in the incidence of laboratory-confirmed influenza.” See: Long, Y. et al. (2020) “Effectiveness of N95 respirators versus surgical masks against influenza: A systematic review and meta-analysis,” See: J Evid Based Med. 2020; 1- 9. https://onlinelibrar...1111/jebm.12381
Again just small meta-analysis (N=6), with shit confidence intervals. Certainly an interesting result, but not to be too heavily weight against contrary findings.
There were no statisti-
cally significant differences in preventing laboratory-confirmed influenza (RR = 1.09, 95% CI 0.92-
1.28, P > .05), laboratory-confirmed respiratory viral infections (RR = 0.89, 95% CI 0.70-1.11),
laboratory-confirmed respiratory infection (RR = 0.74, 95% CI 0.42-1.29) and influenzalike ill-
ness (RR = 0.61, 95% CI 0.33-1.14) using N95 respirators and surgical masks. Meta-analysis indi-
cated a protective effect of N95 respirators against laboratory-confirmed bacterial colonization
(RR = 0.58, 95% CI 0.43-0.78).
My conclusion is there is no reason to suggest masks don't help, and further that there is no reason to wish that this were false.
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Let's now take a look the other side of the coin, and see some of the studies I read (as early as April or May) that convinced me wearing a mask was likely a wise move.
A few of these are preview releases, accepted manuscripts awaiting peer-review.. but overall they seem to suggest the cautious attitude of wearing masks to me.
Professional and Home-Made Face Masks Reduce Exposure to Respiratory Infections among the General Population
Marianne van der Sande1*, Peter Teunis1,2, Rob Sabel3
1 National Institute for Public Health and the Environment (RIVM), Bilthoven, Netherlands, 2 Hubert Department of Global Health, Rollins School of Public Health, Emory
University, Atlanta, Georgia, United States of America, 3 Netherlands Organisation for Applied Scientific Research (TNO), Rijswijk, Netherlands
Abstract
Background: Governments are preparing for a potential influenza pandemic. Therefore they need data to assess the
possible impact of interventions. Face-masks worn by the general population could be an accessible and affordable
intervention, if effective when worn under routine circumstances.
Methodology: We assessed transmission reduction potential provided by personal respirators, surgical masks and home-
made masks when worn during a variety of activities by healthy volunteers and a simulated patient.
Principal Findings: All types of masks reduced aerosol exposure, relatively stable over time, unaffected by duration of wear
or type of activity, but with a high degree of individual variation. Personal respirators were more efficient than surgical
masks, which were more efficient than home-made masks. Regardless of mask type, children were less well protected.
Outward protection (mask wearing by a mechanical head) was less effective than inward protection (mask wearing by
healthy volunteers).
Conclusions/Significance: Any type of general mask use is likely to decrease viral exposure and infection risk on a
population level, in spite of imperfect fit and imperfect adherence, personal respirators providing most protection. Masks
worn by patients may not offer as great a degree of protection against aerosol transmission.
Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis
Derek K Chu, Elie A Akl, Stephanie Duda, Karla Solo, Sally Yaacoub, Holger J Schünemann, on behalf of the COVID-19 Systematic Urgent Review
Group Effort (SURGE) study authors*
Summary
Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19 and is spread person
to person through close contact. We aimed to investigate the effects of physical distance, face masks, and eye
protection on virus transmission in health-care and non-health-care (eg, community) settings.
Methods We did a systematic review and meta-analysis to investigate the optimum distance for avoiding person
to person virus transmission and to assess the use of face masks and eye protection to prevent transmission of viruses.
We obtained data for SARS-CoV-2 and the betacoronaviruses that cause severe acute respiratory syndrome, and
Middle East respiratory syndrome from 21 standard WHO-specific and COVID-19-specific sources. We searched
these data sources from database inception to May 3, 2020, with no restriction by language, for comparative studies
and for contextual factors of acceptability, feasibility, resource use, and equity. We screened records, extracted data,
and assessed risk of bias in duplicate. We did frequentist and Bayesian meta-analyses and random-effects metaregressions.
We rated the certainty of evidence according to Cochrane methods and the GRADE approach. This study is registered with PROSPERO, CRD42020177047.
Findings Our search identified 172 observational studies across 16 countries and six continents, with no randomised
controlled trials and 44 relevant comparative studies in health-care and non-health-care settings (n=25 697 patients).
Transmission of viruses was lower with physical distancing of 1 m or more, compared with a distance of less than 1 m
(n=10 736, pooled adjusted odds ratio [aOR] 0·18, 95% CI 0·09 to 0·38; risk difference [RD] –10·2%, 95% CI
–11·5 to –7·5; moderate certainty); protection was increased as distance was lengthened (change in relative risk
[RR] 2·02 per m; pinteraction=0·041; moderate certainty). Face mask use could result in a large reduction in risk of
infection (n=2647; aOR 0·15, 95% CI 0·07 to 0·34, RD –14·3%, –15·9 to –10·7; low certainty), with stronger
associations with N95 or similar respirators compared with disposable surgical masks or similar (eg, reusable
12–16-layer cotton masks; pinteraction=0·090; posterior probability >95%, low certainty). Eye protection also was associated
with less infection (n=3713; aOR 0·22, 95% CI 0·12 to 0·39, RD –10·6%, 95% CI –12·5 to –7·7; low certainty).
Unadjusted studies and subgroup and sensitivity analyses showed similar findings.
Interpretation The findings of this systematic review and meta-analysis support physical distancing of 1 m or more
and provide quantitative estimates for models and contact tracing to inform policy. Optimum use of face masks,
respirators, and eye protection in public and health-care settings should be informed by these findings and contextual
factors. Robust randomised trials are needed to better inform the evidence for these interventions, but this systematic
appraisal of currently best available evidence might inform interim guidance.
Accepted manuscript
Surgical mask partition reduces the risk of non-contact transmission in a golden Syrian hamster model for Coronavirus Disease 2019 (COVID-19)
Jasper Fuk-Woo Chan, Shuofeng Yuan, Anna Jinxia Zhang, Vincent Kwok-Man Poon, Chris Chung-Sing Chan, Andrew Chak-Yiu Lee, Zhimeng Fan, Can Li, Ronghui Liang, Jianli Cao ... Show more
Clinical Infectious Diseases, ciaa644, https://doi.org/10.1093/cid/ciaa644
Published: 30 May 2020
Background
Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is believed to be mostly transmitted by medium-to-large sized respiratory droplets although airborne transmission is theoretically possible in healthcare settings involving aerosol-generating procedures. Exposure to respiratory droplets can theoretically be reduced by surgical mask usage. However, there is a lack of experimental evidence supporting surgical mask usage for prevention of COVID-19.
Methods
We used a well-established golden Syrian hamster SARS-CoV-2 model. We placed SARS-CoV-2-challenged index hamsters and naïve hamsters into closed system units each comprising two different cages separated by a polyvinyl chloride air porous partition with unidirectional airflow within the isolator. The effect of a surgical mask partition placed in between the cages was investigated. Besides clinical scoring, hamster specimens were tested for viral load, histopathology, and viral nucleocapsid antigen expression.
Results
Non-contact transmission was found in 66.7% (10/15) of exposed naïve hamsters. Surgical mask partition for challenged index or naïve hamsters significantly reduced transmission to 25% (6/24, P=0.018). Surgical mask partition for challenged index hamsters significantly reduced transmission to only 16.7% (2/12, P=0.019) of exposed naïve hamsters. Unlike the severe COVID-19 manifestations of challenged hamsters, infected naïve hamsters had lower clinical scores, milder histopathological changes, and lower viral nucleocapsid antigen expression in respiratory tract tissues.
Conclusions
SARS-CoV-2 could be transmitted by respiratory droplets or airborne droplet nuclei in the hamster model. Such transmission could be reduced by surgical mask usage, especially when masks were worn by infected individuals.
Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic?
Objective
This study examined homemade masks as an alternative to commercial face masks.
Methods
Several household materials were evaluated for the capacity to block bacterial and viral aerosols. Twenty-one healthy volunteers made their own face masks from cotton t-shirts; the masks were then tested for fit. The number of microorganisms isolated from coughs of healthy volunteers wearing their homemade mask, a surgical mask, or no mask was compared using several air-sampling techniques.
Results
The median-fit factor of the homemade masks was one-half that of the surgical masks. Both masks significantly reduced the number of microorganisms expelled by volunteers, although the surgical mask was 3 times more effective in blocking transmission than the homemade mask.
Conclusion
Our findings suggest that a homemade mask should only be considered as a last resort to prevent droplet transmission from infected individuals, but it would be better than no protection. (Disaster Med Public Health Preparedness. 2013;0:1–6)
New study suggests wearing a face mask at home could help limit spread of COVID-19
Published Thursday, May 28, 2020 6:30PM EDT
TORONTO -- A new study has found that wearing a face mask in your home could help reduce the risk of spreading the coronavirus among those you live with.
Researchers from China, the U.S., and Australia carried out the retrospective cohort study between Feb. 28 and March 27, surveying 335 people from 124 families in Beijing, China, that had lived in the same house for at least four days prior and for more than a day after a person who had tested positive for COVID-19 started showing symptoms.
The researchers specifically focused on secondary cases of transmission of the virus, and how it spread in close contact situations, such as eating around a table or watching television, from someone in a household to other family members before the infected person became symptomatic.
Associations between wearing masks, washing hands, and social distancing practices, and risk of COVID-19 infection in public: a cohort-based case-control study in Thailand
Summary
Background. Effectiveness of personal protective measure against COVID-19 infection is largely
unknown.
Methods. We conducted a retrospective case-control study, using a cohort of contact tracing records in Thailand. A total of 1,050 asymptomatic contacts of COVID-19 patients between 1 and 31 March 2020 were retrospectively interviewed by phone about their protective measures against COVID-19 infection. Cases were defined as asymptomatic contacts who were diagnosed with COVID-19 by 21 April 2020. Multilevel mixed-effect logistic regression models were used
Findings. Overall, 211 (20%) were diagnosed with COVID-19 by 21 Apr 2020 (case group) while 839 (80%) were not (control group). Fourteen percent of cases (29/210) and 24% of controls (198/823) reported wearing either non-medical or medical masks all the time during the contact
period. Wearing masks all the time (adjusted odds ratio [aOR] 0.23; 95%CI 0.09-0.60) was independently associated with lower risk of COVID-19 infection compared to not wearing masks, while wearing masks sometimes (aOR 0.87; 95%CI 0.41-1.84) was not. Shortest distance of
contact >1 meter (aOR 0.15; 95%CI 0.04-0.63), duration of close contact ≤15 minutes (aOR 0.24; 95%CI 0.07-0.90) and washing hands often (aOR 0.33; 95%CI 0.13-0.87) were significantly associated with lower risk of infection. Sharing a cigarette (aOR 3.47; 95%CI 1.09-11.02) was
associated with higher risk of infection. Those who wore masks all the time were more likely to wash hands and practice social distancing. We estimated that if everyone wore a mask all the time, washed hands often, did not share a dish, cup or cigarette, maintained distances >1 meter and spent ≤15 minutes with close contacts, cases would have been reduced by 84%.
Interpretation. Our findings support consistently wearing masks, washing hands, and social distancing in public to protect against COVID-19 infections. Combining measures could substantially reduce infections in Thailand.
Absence of Apparent Transmission of SARS-CoV-2 from Two Stylists After Exposure at a Hair Salon with a Universal Face Covering Policy — Springfield, Missouri, May 2020
Weekly / July 17, 2020 / 69(28);930-932
On July 14, 2020, this report was posted online as an MMWR Early Release.
M. Joshua Hendrix, MD1; Charles Walde, MD2; Kendra Findley, MS3; Robin Trotman, DO4 (View author affiliations)
Among 139 clients exposed to two symptomatic hair stylists with confirmed COVID-19 while both the stylists and the clients wore face masks, no symptomatic secondary cases were reported; among 67 clients tested for SARS-CoV-2, all test results were negative. Adherence to the community’s and company’s face-covering policy likely mitigated spread of SARS-CoV-2.
What are the implications for public health practice?
As stay-at-home orders are lifted, professional and social interactions in the community will present more opportunities for spread of SARS-CoV-2. Broader implementation of face covering policies could mitigate the spread of infection in the general population.
Face Masks Considerably Reduce Covid-19 Cases in Germany
Abstract
We use the synthetic control method to analyze the effect of face masks on the spread of Covid-19 in Germany. Our identification approach exploits regional variation in the point in time when face masks became compulsory. Depending on the region we analyse, we find that face masks reduced the cumulative number of registered Covid-19 cases between 2.3% and 13% over a period of 10 days after they became compulsory. Assessing the credibility of the various estimates, we conclude that face masks reduce the daily growth rate of reported infections by around 40%.
Edited by caliban, 18 July 2020 - 02:02 PM.
moved & cleaned
:
but is that video proving the micro-droplets going through the mask?
