Scientific Brief from the CDC on using masks to control the spread of the Covid-19 virus

 From the Website of the Centers for Disease Control, 11/10/20

Scientific Brief: Community Use of Cloth Masks to Control the Spread of SARS-CoV-2
Updated Nov. 10, 2020

The brief includes 45 references to substantiate the CDC claims about wearing masks. Link to the Website to see the complete article with references. Here is the brief:

Background

SARS-CoV-2 infection is transmitted predominately by respiratory droplets generated when people cough, sneeze, sing, talk, or breathe. CDC recommends community use of masks, specifically non-valved multi-layer cloth masks, to prevent transmission of SARS-CoV-2. Masks are primarily intended to reduce the emission of virus-laden droplets (“source control”), which is especially relevant for asymptomatic or presymptomatic infected wearers who feel well and may be unaware of their infectiousness to others, and who are estimated to account for more than 50% of transmissions.1,2 [emphasis added] Masks also help reduce inhalation of these droplets by the wearer (“filtration for personal protection”). The community benefit of masking for SARS-CoV-2 control is due to the combination of these effects; individual prevention benefit increases with increasing numbers of people using masks consistently and correctly.

Source Control to Block Exhaled Virus 

Multi-layer cloth masks block release of exhaled respiratory particles into the environment,3-6 along with the microorganisms these particles carry.7,8 Cloth masks not only effectively block most large droplets (i.e., 20-30 microns and larger)9 but they can also block the exhalation of fine droplets and particles (also often referred to as aerosols) smaller than 10 microns ;3,5 which increase in number with the volume of speech10-12 and specific types of phonation.13 Multi-layer cloth masks can both block up to 50-70% of these fine droplets and particles3,14 and limit the forward spread of those that are not captured.5,6,15,16 Upwards of 80% blockage has been achieved in human experiments that have measured blocking of all respiratory droplets,4 with cloth masks in some studies performing on par with surgical masks as barriers for source control.3,9,14

Filtration for Personal Protection 

Studies demonstrate that cloth mask materials can also reduce wearers’ exposure to infectious droplets through filtration, including filtration of fine droplets and particles less than 10 microns. The relative filtration effectiveness of various masks has varied widely across studies, in large part due to variation in experimental design and particle sizes analyzed. Multiple layers of cloth with higher thread counts have demonstrated superior performance compared to single layers of cloth with lower thread counts, in some cases filtering nearly 50% of fine particles less than 1 micron.14,17-29 Some materials (e.g., polypropylene) may enhance filtering effectiveness by generating triboelectric charge (a form of static electricity) that enhances capture of charged particles18,30 while others (e.g., silk) may help repel moist droplets31 and reduce fabric wetting and thus maintain breathability and comfort.

Human Studies of Masking and SARS-CoV-2 Transmission 

Data regarding the “real-world” effectiveness of community masking are limited to observational and epidemiological studies.

• An investigation of a high-exposure event, in which 2 symptomatically ill hair stylists interacted for an average of 15 minutes with each of 139 clients during an 8-day period, found that none of the 67 clients who subsequently consented to an interview and testing developed infection. The stylists and all clients universally wore masks in the salon as required by local ordinance and company policy at the time.32
• In a study of 124 Beijing households with > 1 laboratory-confirmed case of SARS-CoV-2 infection, mask use by the index patient and family contacts before the index patient developed symptoms reduced secondary transmission within the households by 79%.33
• A retrospective case-control study from Thailand documented that, among more than 1,000 persons interviewed as part of contact tracing investigations, those who reported having always worn a mask during high-risk exposures experienced a greater than 70% reduced risk of acquiring infection compared with persons who did not wear masks under these circumstances.34
• A study of an outbreak aboard the USS Theodore Roosevelt, an environment notable for congregate living quarters and close working environments, found that use of face coverings on-board was associated with a 70% reduced risk.35
• Investigations involving infected passengers aboard flights longer than 10 hours strongly suggest that masking prevented in-flight transmissions, as demonstrated by the absence of infection developing in other passengers and crew in the 14 days following exposure.36,37

Seven studies have confirmed the benefit of universal masking in community level analyses: in a unified hospital system,38 a German city,39 a U.S. state,40 a panel of 15 U.S. states and Washington, D.C.,41,42 as well as both Canada43 and the U.S.44 nationally. Each analysis demonstrated that, following directives from organizational and political leadership for universal masking, new infections fell significantly. Two of these studies42,44 and an additional analysis of data from 200 countries that included the U.S.45 also demonstrated reductions in mortality. An economic analysis using U.S. data found that, given these effects, increasing universal masking by 15% could prevent the need for lockdowns and reduce associated losses of up to $1 trillion or about 5% of gross domestic product.42  [emphasis added]

Conclusions 

Experimental and epidemiological data support community masking to reduce the spread of SARS-CoV-2. The prevention benefit of masking is derived from the combination of source control and personal protection for the mask wearer. The relationship between source control and personal protection is likely complementary and possibly synergistic14, so that individual benefit increases with increasing community mask use. Further research is needed to expand the evidence base for the protective effect of cloth masks and in particular to identify the combinations of materials that maximize both their blocking and filtering effectiveness, as well as fit, comfort, durability, and consumer appeal. Adopting universal masking policies can help avert future lockdowns, especially if combined with other non-pharmaceutical interventions such as social distancing, hand hygiene, and adequate ventilation. [emphasis added]

Preventing the spread of COVID-19 during colder weather

An article from USA Today has some good advice about staying safe indoors as Covid cases are rising in most parts of the country: “Fauci warns against Thanksgiving celebrations: How to stay safe indoors from the coronavirus during cold seasons” by Adrianna Rodriguez, 10/16/20.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, has become a target for people who irrationally blame Covid and the fallout from the virus on him as the bearer of news that they do not want to hear. In his defense, Dr. Fauci is not banning Thanksgiving. He is just warning that gatherings of people at events like this can turn into tragic super spreaders of the virus. Read the full artlcle for specifics on how to function safely in indoor environments. Here are some excerpts:

“Officials have been able to control COVID-19 transmission rates by implementing policies that encourage residents to eat and drink, exercise and spend time with friends and loved ones at a safe distance outside. 

“But health experts are concerned cases could spike again as cooler temperatures in the fall and winter force people back indoors. 

“The nation's leading infectious disease expert, Dr. Anthony Fauci, also is concerned upcoming holiday celebrations could increase transmission rates and advised Americans to skip any big Thanksgiving plans. 

“Speaking to 'CBS Evening News' Wednesday, Fauci cautioned against 'gathering together in an indoor setting' with large groups of out-of-town guests. 'It is unfortunate because that’s such a sacred part of American tradition – the family gathering around Thanksgiving,' he said. 'But that is a risk.'“ 

The article goes on to explain how improving ventilation indoors, prevents transmission of the virus:

“Dr. Lewis Nelson, professor and chair of emergency medicine at Rutgers New Jersey Medical School, said one of the main reasons there’s a higher risk of transmission indoors than outdoors is lack of ventilation.

“'Natural air currents outside disperse virus particles more quickly and effectively than inside. There’s minimal to no air circulation indoors, allowing virus particles to linger in the air or fall on high-touch surfaces.'…

[See more on this subject: "Ventilation and air filtration play a key role in preventing the spread of COVID-19 indoors" by Ramon Padilla, USA TODAY, 10/19/20]

The article also encourages the continued use of masks and social distancing and emphasizes keeping an eye on community transmission rates:

“Although mask-wearing, social distancing, hand hygiene and increased airflow can reduce the risk of transmission indoors, these mitigation efforts aren't 100% effective, especially if community transmission rates are high.

“Barry Bloom, research professor of public health and former dean of Harvard T.H. Chan School of Public Health, recommends residents keep an eye on transmission rates in their area to determine if it’s safe to go to an indoor public setting.”

In general, the recommendations for preventing spread of the virus remain the same, whether indoors or outside in public spaces and for the same reasons. The Covid-19 virus is very contagious and is spread from one person to another, mostly through the air in droplets and aerosols that contain the virus. The droplets and aerosols are expelled by a contagious person during breathing, talking, singing, exercising, and other activities. 

The likelihood of contracting the virus increases with the amount of virus one is exposed to over time. Without a cure for the disease or the availability of vaccines, preventing the spread of the virus relies on some standard public health measures such as quarantining people who are known to be infected, wearing masks, physical distancing, and improving ventilation to lower the concentration of the virus to safer levels. Frequent hand-washing takes care of virus that may be picked up from contaminated surfaces and transferred to ones nose, mouth, or eyes. 

From what I understand, when the virus lodges deep in the lungs, it replicates and spreads infection to the rest of the body. An infected person may have no symptoms at all or their symptoms may be catastrophic. Short of death, survivors of the virus can have severe damage to organs and in some people it appears to be a chronic disease, but it is too soon to know exactly what the long term effects are from contracting the virus.

Masks have been as much maligned as Dr. Fauci. Depending on the mask, even a homemade two-layered cloth mask is a good barrier to spreading the virus. It does not filter out separate virus particles, but it does prevent the transmission of droplets, which is where the virus lurks in most instances. The primary purpose of wearing a mask is to protect others if you happen to be contagious and don’t know it. It may also help the wearer of the mask by stopping droplets from a contagious person, but this is not the primary purpose for wearing a mask.

While masks are not recommended for very young children or for people like my disabled sons who cannot remove the mask themselves, they can be worn safely by most people. My boys have worn masks to medical appointments, but they are always with a caregiver who would recognize if a mask was causing them distress.

Contrary to reports from people opposing mask mandates, masks have not been found to lower oxygen levels or raise CO2 levels. See “Fact check: Experts say face masks don't cause oxygen deprivation, neurological damage” by Devan Patel, USATODAY, 10/17/20: 

“‘While masks can block particles like respiratory droplets and aerosols that might contain coronavirus, they do not block gases like oxygen and carbon dioxide,’ said Linsey Marr, a professor of civil and environmental engineering at Virginia Tech and an expert in airborne disease transmission. ‘A recent study of people wearing surgical masks while walking around found no significant changes in carbon dioxide in their breath nor oxygen in their blood, compared to walking without a mask.’”

The article concludes,

“Though the neurological damage described can occur when there is oxygen deprivation, medical experts say there is no evidence linking either to wearing masks.

“Medical studies have shown a link between COVID-19 and those very neurological effects, meaning the decision to not to wear a mask puts people at a higher risk of experiencing them.”

So what are the arguments against wearing a mask? This is a YouTube video of citizen anti-mask activists from Palm Beach County, Florida, on June 26, 2020. I find their arguments bizarre and not helpful in getting to any understanding of why mask wearing may be harmful or unwarranted, other than they just don't like being told what to do: Mask wearing is "against God’s will”, they say, and it is “practicing the devil’s law”; requiring masks is a crime against humanity; social distancing trains us up to follow military protocol; it’s all Bill Gates’ fault and 5G has something to do with it; and surely satanism, pedophilia, and death will follow mandates for the wearing of masks. 

Wearing a mask in public spaces to prevent the spread of a contagious virus does not infringe on anyone’s liberty any more than following laws that require us to stop at red lights or to wear shoes in restaurants. It is in fact an easy and inexpensive way to slow the spread to get the virus under control so that the economy can recover. This happened in Arizona when the state took measures to stop the spread of the virus:

"COVID-19 cases in Arizona dropped 75% after mask mandates began, report says" by Stephanie Innes, Arizona Republic,10/9/20. 

I don’t like wearing a mask for long periods of time, but I owe it to the people who have to work in places where they come in frequent contact with the public, including grocery store clerks, the pharmacist where I pick up my medications, medical workers who take care of my son Danny when he lands in the ER for uncontrolled seizures, and many more. For people who cannot tolerate a mask for whatever reason, there are many alternatives to buying essential items that don’t involve in-person shopping. Even church services have been modified to ensure social distancing and safety. 

Getting control of Covid-19 has dragged on for far too long. When it appears that there is no end in sight, the danger is in giving up and giving in to a wildly out of control pandemic. We deserve better than that and the control of the virus is still within our grasp while we wait for vaccines, better treatments, and cures.