Wearing a mask by general public in private and social life during the COVID-19 epidemic has different approaches. This post presents my personal opinion which has been gradually formed by emerging facts and deeper understanding of the current epidemiological situation. However, unfortunately, we have minimal scientifically supported data and maximal fear-mongering statements. The main goal of this post is in presenting rationality of mask wearing in private life.
This post violates the rules of the short size of a Blog’s entry. The subject requires a comprehensive presentation because the mask wearing issue became a civil life event.
The readers, who are in haste to conclusions, can omit some pages. Many details reflect some of my literature research work which support my opinion. The most available sources are related to influenzas and prior coronavirus epidemics. World Health Organization (WHO) separated COVID-19 from other coronaviruses outbreaks. Without going in the politically charged viruses classification terminology, SARS-CoV-2 virus is the closest relative of SARS-CoV, first cousin. For the wearing a mask issue, these viruses discharge pattern is the same.
Only in rare occasions, some references are provided, because this post is not a scientific study. It is rather an opinion on the background of pathophysiology, environment physics, my experience as a laboratory practitioner, and… some common sense.
Elective masks’ classification
Surgical operational mask
The surgical mask serves to protect the operation field and the operative room from infectious contamination. The use of this kind of masks is undisputable. Now even dental hygienists use them though also for self-protection.
Mask for an ill person
Wearing a mask by an ill person with symptoms of potentially infectious discharge (or even without) is in the same line, although more nuanced, as a surgical mask. Even positively tested, as socially considerate citizens, might be required to wear one, if they would not be in a quarantine confinement. This issue along with rationality of testing itself requires special discussion.
Professional PPE mask
Masks, as part of Personal Protective Equipment (PPE) predominately in anatomic pathology laboratory, were discussed in previous posts. OSHA regulation are the bottom line with some variant depending on the local implementation. The principles can be extrapolated to other areas in medical field with some correction of the assigned procedures, especially during the care for COVID-19 patients in the acute stage of the disease.
Mask as part of civilian life, a “street mask”
The current post is going to touch on the topic of wearing a mask which can loosely be called a private life mask, or elected mask, or civilian mask, or casual mask, or a “street mask” or any better name during the COVID-19 epidemic.
Since April 12th, wearing a mask outdoors is mandatory in Israel. Although there some exceptions for certain categories of situations, such a ruling for the entire country requires a close look. Is not unjustified fear or other, including political considerations, influence such decision? Is there a reliable research support?
There is a no-love triangle in the epidemic outbreak where the mask, the object of this post, has been caught in the middle. The Diagram presents the participants which cannot be separate in real live, but need to be discussed separately for the sake of a comprehensive approach. The virus, the culprit, being on the top of the triangle in the ambient environment is infecting individuals. Their encounter creates an epidemiological “crime scene”.
Virus: the intruder, the culprit
Supposedly, we have reliable information about SARS-CoV-2 virus (or COVID-19 virus), when human-to-human transmission of the SARS-CoV-2 in Wuhan, China, began in December 2019. The name SARS-CoV-2 virus was selected by International Committee on Taxonomy of Viruses due to the nucleotide sequence similar to SARS-CoV which caused the 2003 SARS epidemic.
SARS-CoV-2 virus is an enveloped particle containing single-stranded RNA associated with a nucleoprotein within a shell of matrix protein. The envelope bears projections which glycoproteins are responsible for attachment to the host cell. After the virus enters the host cell and uncoats, the genome is transcribed and then translated. The mRNAs form a unique “nested set” by budding from host cell membranes. This is a short description of the virus’s initial nefarious behavior in the infected area.
Person: the host, the victim
An incoming coronavirus needs to find epithelial cells to invade the host. It intrudes predominately into the respiratory tract. The intrinsic barrier on the mucosal surface of the respiratory epithelium provides the first line of defense against respiratory viruses. Mucus layers can effectively trap the virus before it can enter the host cells. Infected cells become vacuolated. Cell damage triggers the production of inflammatory mediators, which in turn increases nasal secretion and causes local inflammation and swelling. Mucociliary Clearance Apparatus (MCC) serves as a key mechanism for eliminating the intruders from the respiratory epithelial surface. If that protection fails, they move toward the larynx, where mucus containing the entrapped virus is swallowed or expectorated (Seasonality of Respiratory Viral Infections. Annual Review of Virology; 2020, 7:2.1–2.19).
This local reaction to the virus intrusion is relevant to the mask wearing topic. These responses stimulate sneezing and obstruct the airway, and raise the temperature of the mucosa or even the body’s temperature. Relationship between temperature, humidity, and COVID-19 virus can increase host’s susceptibility to infections. Inhalation of cold dry air directly affects the upper airway mucosa, impairs mucociliary clearance, and increases mucin production, as well as potentially causing epithelial damage.
The subject of this post is the protective mask. It is important to visualize what happens when the virus is leaving the infected nasopharyngeal and orotracheal areas, through sneezing, coughing, even speaking, and perhaps just in minimal skin contact in form of snot, sputum, saliva, and skin cornea. The virus is not “naked” (it is impossible), but now it is coated by mucus and large and small droplets of water that depends very much on air humidity. Components of the mucus are 93– 97% w/w water.
Epidemiological crime scene encounter
Respiratory virus infection can occur through:
(a) direct contact,
Direct contact transmission occurs either indirectly through contact with infected (by virus) secretions or directly through physical touch between an infected individual and a susceptible person. Just common sense, it cannot be managed by mask or its absence.
Droplet spray in shortrange transmission can be prevented by a mask. This is a purpose of the mask as part of PPE. Droplet transmission requires the source of infectious to directly spray large droplets by coughing or sneezing onto mucous surfaces or eye conjunctiva of a susceptible person.
The overwhelming majority of person-to-person transmission happens indoors through discharge by an ill person through droplet spray in shortrange transmission. Wearing a mask by an ill person, besides apparent rationale of preventing the discharge of the virus, requires a closer look at scientific data which support this notion. The load of infections material, frequency of encounters, proximity from the individual with discharge, and other epidemiological details require scientifically reliable data.
A direct quote from an article: “In order for droplet transmission to occur infected and susceptible persons have to be in close contact (several tens of cm apart), of comparable height and the sneeze or cough has to be directed in the “right” direction. The stopping distances of expelled particles provide another telling illustration of the complexities involved in droplet transmission: particles smaller than 488 μm (cough) or 232 μm (sneeze) will not travel further than 60 cm. (Quantifying the routes of transmission for pandemic influenza. Bulletin of Mathematical Biology. 2008; 70:820–867). Although these data are related to influenza viruses, the physical properties of a droplets are the same. They punch a hole in the established in 1930th 6 feet (2 meters) distance notion (Wells WF. On air-borne infection. Study II. Droplets and droplet nuclei. American Journal of Hygiene. 1934; 20:611–618). A researcher in MIT from Fluid Dynamics of Disease Transmission Laboratory, however, found the distance should be 27 feet (810 cm) or even more due to turbulent gas cloud dynamics during sneezing by infected person (Turbulent Gas Clouds and Respiratory Pathogen Emissions. Potential Implications for Reducing Transmission of COVI-19. JAMA online, March, 26, 2020).
In a close expiratory event, a close cough is unlikely (≈1% probability) to generate traditional droplet transmission (i.e., direct deposition on the mucous membranes), although a close, unprotected and horizontally-directed sneeze is potent enough to cause droplet transmission (Quantifying the routes of transmission for pandemic influenza. Bulletin of Mathematical Biology. 2008; 70:820–867).
Virus inactivation should be taken into account, as well as gravitational settling of particles with supposedly viruses. This understanding can contribute to rational use of the mask under certain working conditions and in private life.
Aerosol transmission is far more dominant than contact transmission for influenza. Aerosol in long-range transmission should be divided into indoors and outdoors transmission. The latter is in the background of the personal mask (“street mask” indoors and outdoors) employment. Airborne transmission through droplet nuclei does not require face-to-face contact with a person who is prone to be infected.
SARS-CoV-2 virus in COVID-19 is completely similar to influenza viruses by the physical features of distribution in droplets transmission. The differences might start at the level when the virus is uncoated from its envelop and start relationship with the invaded host.
Indoors transmission occurs as droplet spray of predominantly large droplets up to millimeters settling directly or by indirect contact on mucous membranes or by inhalation of either large respiratory droplets (>10 μm in diameter) or small airborne droplet nuclei (<5 μm in diameter). Transmission requires the direct deposition of large droplets on the mucosa of a susceptible person. The only mechanisms that occur immediately after expulsion (<1 s) are in a restricted space.
Outdoors, transmission occurs at close ranges rather than over long distances. The airborne transmission in this situation is unlikely to be of significance in most clinical settings. (Transmission of influenza A in human beings. Lancet Infect. Dis. 2007. 7:257–65). Outdoor aerosol transmission is not likely due to dilution and dispersion by ambient wind speeds and turbulence, whereas in closed environments, particularly with low ventilation, aerosol transmission is more likely. (High infectivity and pathogenicity of influenza A virus via aerosol and droplet transmission. Epidemics. Volume 2, Issue 4, December 2010, Pages 215-222).
The low humidity and lower temperature environment would promote the viability of SARS-CoV-2 in the droplets and impaired ciliary clearance and innate immune defense, for robust access to the deep lung tissue and rapid transmission between infected individuals.
Stability of Respiratory Viruses
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. There are some statements that 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, and they provide information for pandemic mitigation efforts. (Aerosol Surface Stability New England Journal Medicine nejm.org on April 12, 2020).
Some sources state that the virus can hang around in the air for at least 3 hours, but this statement does not have a reliable experimental support. A special study reports the virus viability 5.6 hours on stainless steel and 6.8 hours on plastic surface. These sporadic data are only partially related to the topic of this post, namely casual mask wearing. They are the decontamination and disinfection issues, which require a separate discussion.
The presented above available to me research data are in the background of my understanding of wearing a protective mask just in private life outside a medical facility, diagnostic or clinical. I am open to changes in my view if new data would look reliable to me.
A special masks comparison discussion will be posted later. Now, I want to discuss the rationality of manufactured or various self-made “masks”, simple improvised scarfs.
Should the use of face masks be recommended during a pandemic on the basis of current knowledge of airborne or droplet transmission?
It looks like airborne transmission is important only indoors. Outdoors, where virus discharge is by dilution, air circulation and higher virus inactivation, the transmission is, in my view, questionable. However, even indoors use of a face mask requires some sober considerations.
If we exclude very exceptionally rare situation when a COVID-19 ill person coughs or sneezes in close proximity (2 feet), the casual face mask is used to protect from viruses that presumably exist in the room. They are distributed diffusely in the area of a person presence. It means, that the same particles of droplets, containing viruses, are at the surface of the mask and other areas of the face (forehead, eyes, remaining part of the cheeks, etc.), as well as hear, hands and cloth equally.
Viruses invade predominately the respiratory tract via the nose or open mouth and less through eye conjunctive. The droplets containing viruses don’t know where the nose is, they don’t have a GPS. The wet and warm mask provides the virus in droplets (droplet nuclei) a comfortable dwelling surface. The mask becomes a hotbed for viruses. When the mask is taken off, the droplets inevitably are disseminated in close proximity to the “infection gates” (nose, mouth, eye conjunctive). The person’s wet and warm breath through the mask also provides the surrounding face’s skin with some additional humidity for viable viruses which would otherwise dry out on the skin’s surface. Semidried droplets become lighter for take off from the skin. By air circulation, hands manipulations and other ways, they can find their way to the nose or mouth because the power of active inhale prevails over power of the passive exhale.
Practical advice: when the face mask is taken off, wash with soap not only your hands but also your face and the exposed parts of the neck.
Breathing through the mask is not the best evolutionary achievement for the humans. The nose is the first line of defense. The nasopharyngeal and oropharyngeal areas are the second lines of immunological defense. Would it not be reasonable to let them do their defense work under natural physiological conditions if some amount of viruses sneaked behind the infection gates? We cannot seal them off from entry of a pathological agent completely.
Very rarely, the masks are taken off according to the infection disease professional rules – slowly rolling with the mask’s outside in. Actually, facial masks designed in the respirators dome form cannot be taken off in this manner. Such way of taking the mask off is also just impossible for an improvised mask made from a kerchief. There are other details of handling the face masks outside the medical facility that makes it, in my view, useless for an individual’s employment and undesirable from epidemiological point.
Community life aspect
We see that almost all people in China are wearing masks. Besides, they are used to wearing them due to living in highly polluted cities, so this is more of a psychological phenomena.
Of course, some exceptions should be made for immunocompromised individuals, but they should be instructed to follow safe use of the mask which should protect them not only from SARS-CoV-2.
Some additional questions
Is a grocery store, supermarket or smaller size store an indoor space during COVID-19?
Do we want a socially devastating life when people move around with Pitbull’s muzzles? How long will this last, and who will decide when it is time to take the masks off? Would it be for now right to go on a date equipped also with gloves, perhaps double gloves just in case, and a respirator? Maybe, a mask will be a part of our attire for a foreseeable future, keeping in mind second waves of many epidemics?
While working on the cytotoxins antibodies history in experimental immunology, I was impressed by how deep immunologists dived into the cell structure. During the current post preparation, I was surprised by how shallow the swims into the infectious epidemiology are in determination of dissemination of airborne infections and immunological responses in population.
Would it not be right, for the institutions in charge of just this current epidemic to arrange simultaneous multiple corroborative and clandestine from each other studies of the infamous 6 feet social distancing? Is not a shame that this distance is based on 90 and 70 years ago studies (WF Wells)? It would not be a long and expensive study.
Is not it time to separate the real knowledge from urban legends in such a serious act of placing the whole country on a complete standstill?
Is the probability theory still a tool for mathematical models based on reliable data?
Meanwhile, let people have some fun in masks creation, like below. Bandanas (Bandannas) now became a fixture of fashion.
However, to make the mask as a part of attire in public areas is , in my view, an unsubstantiated overkill. The society would pay a substantial price for such self-destruction.