Epidemiological aspect of COVID-19 testing

Some excerpts from the news

US Food and Drug Administration (FDA) commissioner Stephen Hahn, MD, is self-quarantining after coming into contact with a person who tested positive for SARS-CoV-2, Reuters reports. Hahn took a diagnostic test and got a negative result. In related news, Katie Miller, press secretary to Vice President Mike Pence, tested positive for SARS-CoV-2 on Friday (5/8/20). Why “in related news”? Why is it the news?

On Saturday, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, and Dr. Robert Redfield, director of the Centers for Disease Control and Prevention, said they will quarantine for 14 days. Both captains on the helm of the epidemic medical management’s ship are in quarantine. The third, Dr. Deborah Birx, the White House Coronavirus Task Force response administrator, challenged the CDC Director “There is nothing from the CDC that I can trust!” Alex M. Azar, the Secretary of Health and Human Services, is not in the news at all. Is the COVID-19 epidemic task force tested three times per day?

Some reminiscences

Reminiscences of my prior experience in epidemiologic practice might influence some bias to current approaches in COVID-19 epidemic.

My first job after medical school, as a doctor, was an epidemiologist position back in Russia, in Karelia near the Finland border in late 1960s. A rural place with scattered collective dairy and fur farms, lumber forest harvest factories surrounded by abounded GULAG camps. Periodic local epidemics were casual as fact of life. Dysentery, hepatitis A among people, sporadic anthrax, tularemia, foot-and -mouth disease among animals. Every epidemic had been managed from the start according infectious epidemiology rules: isolation, testing, hospitalization, local quarantine, disinfection, sanitary. In some occasions, the efforts to decrease the epidemic failed despite all standard efforts. One of the suspected culprits was the continuation of testing. When the testing was limited only to clinical necessity, the epidemic abruptly subsided. Until today, I do not have a rational explanation. Hypothetical thoughts are still lingering.

Some excerpts from basic epidemiology

Common sense and humans experience determine one of the main infectious epidemiology rules as the detection of infected to isolate from the population, as a rotten apple. Testing is an apparent solution. This post is intended to explore the testing notion as epidemiology tool to overcome the spread of COVID-19 epidemic in the USA.

Testing of patients, which require hospitalization or other clinical actions, is an apparent necessity for the differential diagnosis and effective treatment. The rest of testing is the epidemiology work routine. The diagram below presents main directions of this work. Testing with a clear plan of actions, which is following positive or negative result, is only are part of them.

The importance of each component is different depending on infection, local conditions, morbidity, mortality etc. etc.  In the case of COVID-19 epidemic, immediate contact testing prevails institutional contacts, while screening testing within a particular facility is incomparably more significant than the exposure testing to individuals. The latter issue requires special detailed discussion, a special post.

Testing priorities

Below is the excerpt from PRIORITIES FOR COVID-19 TESTING section Evaluating and Testing Persons for Coronavirus Disease 2019 (COVID-19) by Center Disease Control and Prevention (CDC). Revisions were made on May 3, 2020

The entire document is pointing in the wrong direction from the epidemiology perspective.  The serious objection would be on the division for High priority and Priority. The division itself and the content of the document reflect, in my view, misunderstanding by CDC strategic goals of actions in the current epidemic.

Practical epidemiology perspective

Below are my considerations regarding priorities in testing based on my prior experience as a practical infectious epidemiologist.

Hospitalized patients with symptoms are already isolated in the hospital. Their test should be done for the differential diagnosis followed by appropriate treatment.

Healthcare facility workers, workers in congregate living settings, and first responders with symptoms are already ill. Their testing is not a priority, but isolation them from contacts during their professional duties would be a priority with following testing just for clinical handling them as patients.

Residents in long-term care facilities or other congregate living settings, including prisons and shelters, with symptoms are really a high priority for separation them from the rest although this epidemiologic action would be right to do immediately even without a testing.

The testing of contacts is the necessity for localization of the source of infection. Although in a case of COVUD-19 epidemic this is a difficult task as usually in an airborne infection, an attempt would be justifiable.

“Persons without symptoms who are prioritized by health departments or clinicians, for any reason, including but not limited to: public health monitoring, sentinel surveillance, or screening of other asymptomatic individuals according to state and local plans.” These groups are a real priority for testing from the epidemiological approach, although they are in the end of the list of priorities. The main problem is that there are not local plans for such prioritizing, at least they are not in the public domain. For example, from Michigan Department of Health and Human Services

This document adds critical infrastructure workers category. The rationale is to diagnose in time infected and take them out for quarantine. When? How often? How? Etc.  This document is in line with Michigan medical officials’ uninformative briefings.

Summary of epidemiological aspect of COVID-19 testing 

First. Separation of the clinical and epidemiologic lines of testing should be clearly formulated in plans and actions.

Second. From the epidemiology perspective, the indication for testing of contacts includes two main groups: immediate contact with a clinically ill person and determination of individuals for testing in a contacts group.  Aggressive and fast testing of infected and especially contacts in congregated living, public, and work settings is effective in the beginning of the epidemic. Screening is important in the case when the source of infection’s spread is unknown. However, screening brings mixed results when the epidemic is to some degree contained.  

Third. The number of tests, as evidence of success in curtailing the epidemic, inevitably leads to relaxation of specimen’s collection, transportation, and the tests’ quality. The latter is accepted by the society as the Sun’s rise on the East. This issue will be discussed in a separate post.

I do not have an illusion that this post will change the course of actions during the current epidemic. Hopefully, my remarks regarding testing during an epidemic might be useful.

Specimen collection for molecular tests

Significance of the specimen collection area for the virus molecular test (nucleic acid amplification tests (NAAT), such as RT-PCR) is apparent.

According to the World Health Organization (WHO):

At minimum, respiratory material should be collected:

upper respiratory specimens: nasopharyngeal and oropharyngeal swab or wash in ambulatory patients;

• and/or lower respiratory specimens: sputum (if produced) and/or endotracheal aspirate or bronchoalveolar lavage in patients with more severe respiratory disease.

Nasopharyngeal and oropharyngeal swabs are the commonly accepted standard. However, it is technically difficult procedure which require professional training. It is more easily present on the diagram than in a real situation (see both diagrams).

Diagram of the nasopharyngeal test specimen collection

Anatomical conditions of nasopharyngeal specimen collection for COVID-19 molecular test. Red arrow- collection swab in, green arrow- swab out.

Collection a nasopharyngeal swab specimen is invasive. Following of the anatomical structure (conches), which is very much individual, require some training, skill and even instruments. Actually, this is a medical procedure. How far the swabs can reach in every collection? Are the swab’s handles calibrated for approximate depth of penetration?  Many technical details can influence the test’s result.

The solution was found for the “testing, testing, testing” mantra.

Remove preference for NP (nasopharyngeal) swabs” is among “Excerpts from CDC Summary of Recent Changes. Revisions were made on April 29, 2020 to reflect the following”.

And now:

In the list of acceptable specimens for initial diagnostic testing for SARS-CoV-2, CDC recommends:

An anterior naris (nasal swab) specimen collected by a healthcare professional or by onsite or home self-collection (using a flocked or spun polyester swab)”.

 The technical difficulty to obtain the specimen for molecular test from the most representative areas was substituted by simple nostril area. This substitution opens the gates to mass testing everywhere.

Drive-through screening centers have been designed and implemented in South Korea (Drive-Through Screening Center for COVID-19: A Safe and Efficient Screening System against Massive Community Outbreak. J Korean Med Sci. Published online Mar 16, 2020.  https://doi.org/10.3346/jkms 2020 Mar 23;35(11). According to the article, this procedure increased testing capacity over 100 tests per day.

The real drive- through when a tested person opens the car’s window and a swab is poked in the nostril. You can see this procedure on the TV screen how.

The U.S. Food and Drug Administration (FDA) authorized option for the Laboratory Corporation of America (LabCorp) COVID-19 RT-PCR Test to permit testing of samples self-collected by patients at home using LabCorp’s Pixel by LabCorp COVID-19 Test home collection kit. A sample collected from the patient’s nose in saline is mailed to a LabCorp lab for testing. According to FDA Commissioner Stephen M. Hahn, M.D. the data demonstrated from at-home patient sample collection is as safe and accurate as sample collection at a doctor’s office, hospital or other testing site. 30 participants (?!) were enrolled in a self-collection study by LabCorp.

This post will explore only nares specimen collection for COVID-19 RT-PCR test from the nostril’s anatomy, histology, and pathophysiology aspect leaving aside clinical, epidemiological, and medical statistic aspects and other details of this type of specimen collection. These issues require a special post.

Nostrils as part of the nasal cavity are initially a continuation of the skin lined with squamous epithelium and different size of hair. Their protective role is in preventing dust entering the respiratory tract, but it serves also of stopping infections materials, especially droplet containing airborne microorganisms. In this regard, droplet nuclei containing SARS-CoV-2 virus are “hanging” on the hair even without touching the surface of the nostril. Squamous epithelium lining of the anterior nares is followed by ciliated epithelium whose cilia form a carpet on which dust settles, as well as droplet nuclei might be engulfed by mucus. The virus, if it is there became the target of first line of immunology defense through intensive mucus production and tool of cellular  (macrophages , T-lymphocyte cells). All these popular biology data are presented here just to show the place where the collection swabs is operating.

By the way, this operation is not completely innocent.  During this collection manipulations, the droplet nuclei might be taken off the defense line provided by nostrils hair and pushed further into nose cavity which would not be right.

Every specimen collection has some uncertainty. Deviation of the standard bring additional confusing data. Is the method of collection reflected in the at the requisition form documents? As an extraordinary exception with the mark.


Positive SARS-CoV-2 virus molecular test is only evidence of virus presence in the nose’s content when the virus hasn’t even interacted with a person ‘s first line of innate immunity defense response.

The nares collection area for the SARS-CoV-2 virus molecular test can be done only as an extraordinary exception with the special mark.  The clinical and epidemiological interpretation of the result should take into account the nares collection area.

Introduction to COVID-19 Tests

Testing became the buzz word in solving the COVID-19 epidemic. The logic behind testing is apparent to everyone. Only the number of tests is discussed. Ashish Jha, director of the Harvard Global Health Institute thinks that 500,000 tests a day is need for the foreseeable future. The U.S. Nationwide COVID-19 testing capacity steadily increased to 145,000 tests a day. The White House unveils coronavirus testing plan to expand testing which are viewed as critical to reopening the economy.

The Michigan state COVID-19 provides Confirmed COVID-19 Cases, but it is unclear what the case means (https://www.michigan.gov/coronavirus/0,9753,7-406-98163_98173—,00.html). More than likely, the number of tested positively. This information or better disinformation only fuels scare- mongering without a real assessment of the epidemiological importance of testing. Remarkably, during the briefing in Kent county in Michigan on April 29th, the Health department refused to answer the direct question about the number of hospitalizations and death cases.

As now became the standard of the public discourse, the approaches to this specifically medical epidemiological issue are divided along the political party line with the underlining background of public fear, politician’s ignorance, and corporate business interests. The uncertainty is only how less than 365 million to test. The solution is vacillating between the test performance in the bank’s lobby or drive- through or ATM. The tendency is in implementing all three options with looming ahead options by mail or even the drone’s involvement.

On the serious note, testing issue requires professional approach cleared from todays fear and politically motivated aggregation with the focus on rational actions in the current epidemic and in the future outbreaks. There some methodology issues which should be solved.

The presented serial of posts will reflect my personal approach. Otherwise why bother to write. It is based on the infectious epidemiologist experience, familiarity with diagnostic immunology, and anatomic pathology practice. Some bias, which stems on experience collected in different time and competely different situations, is inevitable. However, the classic epidemiology rules still apply.

The diagram presents main variants of testing during COVID-19 epidemic.Molecular test is carried out by  Reverse Transcription Polymerase Chain Reaction (rRT-PCR) for the qualitative detection of nucleic acid from SARS-CoV-2 in upper and lower respiratory specimens. Serum test are in determination of antibodies in plasma to SARS-CoV-2 virus.

Main variants of testing during COVID-19 epidemic.

U.S. Food and Drug Administration (FDA) has issued the first emergency use authorization (EUA) for a COVID-19 Antigen test in May. Antigen test is a “hybrid” test by the diagnostic purpose is closer  to the molecular test, a sort of molecular test light. It will be discussed in a special post later.

The next posts will discuss the testing options separately. There are many details which are not discussed although they are crucial for the test’s implementation and the desired outcome.

Introduction to COVID-19 pandemic

The wildfire of the COVID-19 pandemic is spreading through the world. The arsonists, all while hiding the matches, are offering their help to clean up the burned places by providing some essential protective necessities – all while being praised by the media which has always been in awe of autocratic regimes, starting with German and Italian fascists and their variants. The local Wuhan, China epidemic became a pandemic. The world has to handle this very much self-inflicted wound.

The tragic death count is on display, and the economic losses are well known, the current quarantine restrictions have changed the lives of people around/throughout the world. However, the unaccounted for result of COVID-19 is apparently a pandemic of fear. As a normal protective mechanism of living species, fear becomes damaging in excess for individuals, and is dangerous for politicians who are operating in the public eye of the masses.

These introductory words preclude my presentation of some issues pertaining predominately to safety in anatomic pathology laboratories under COVID-19 conditions. However, the observations and recommendations can be extrapolated to other individual and collective safety issues. They are written from the perspective of my experience as a Chief of Sanitary-Epidemiological Station back in Karelia, Russia, an experimental immunologist (PhD program), a clinical and anatomic pathologist (Leningrad-St. Petersburg), a pathologists’ assistant (including morgue attendant) and grossing technologist (Chicago).

As an epidemiologist, I was obliged to manage all ranges of actions during local epidemics including dysentery, hepatitis, and some sporadic cases of anthrax, tularemia, and others. While working in anatomic pathology, I tried to follow the safety rule, although I managed to accidentally stick my finger during an autopsy of a deceased acute HIV patient. The variability of conditions in individuals’ lives and work across different countries are incomparable. Every experience is limited and personal biases are inevitable, but the common denominator remains to be the rationality of actions under current circumstances.A different perspective might be useful for current COVID-19 and epidemics in the future.

This blog is focusing on “hot” topics. Three buzz words are dominating during current COVID-19 epidemic: hand washing, mask, social distancing with testing inside this triangle.

Hand washing, as a variant of disinfection, is self-explanatory action rooted in history of fighting epidemics. A mask is a natural instinct of locking the door before an intruder breaks in. Social distancing is a relatively new notion. Separation between potentially ill people at the voluntary chosen distance of 6 feet is relatively benign and acceptable by the frightened society. Are not self-destructive for humans prolonged social quarantines of healthy millions who want to work, go for shoping, come together for sport, entertainment, political, religious and other events?

The blog is going to address these issues in detail. They are not challenged in public and even science discourse. Surprisingly, the world entered the pandemic without reliable scientific data regarding these basic premises.

Please, come back to the Blog’s COVID-19 categories. I’m often placing new and periodically updating some previous posts.

COVID-19 and the Mask


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,

 (b) droplet spray in shortrange transmission, or

 (c) aerosol in long-range transmission (airborne transmission).

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).

Airborne transmission is only important indoors. Outdoors, where virus discharge is by dilution, air circulation and higher virus inactivation, the transmission is, in my view, questionable.

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.

Infection part

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.

Epidemiological concern   

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.  

N95 and other Masks


This post is a comparative review of different types of protective masks which are used or suggested for use during the COVID-19 epidemic. These materials are continuation of the previous post COVID-19 and the Mask where some “theoretical” data the about SARS-CoV-2 virus and conditions of the virus distribution are discussed. N95 respirator is the most popular protective mask. It will be discussed in some detail.

Surgical mask

Surgical mask, the mother of all protective masks, was tested more than 100 years. However, it was designed to protect the s space of manipulation from the care provider’s infectious contamination, as well as the ambient environment, namely the room.

 Surgical mask, the older variant

Current variant of a surgical mask

Optimal professional mask in a health care facility with suspected SARS-CoV-2 virus

Below is the optimal professional protective mask with or without a respirator for an anesthesiologist, respiratory therapist, or other person in charge for work with a patient on the ventilator for a short time of the actual procedure management.


The N95 respirator on the figure B looks superfluous, but perhaps, for operational purpose when the anesthesiologist spends the most time in procedures which do not assume the direct contact with the patient discharging infectious material.

N95 respirator

3M respirator

Different types of N95 respirators/masks

Respirators are used predominately in construction, sometimes agriculture, and in healthcare for protection against airborne infections, including viruses and now in COVID-19 epidemic.

Respirators are tested in the direction of inspiration (from outside to inside). The tests take into account the efficiency of the filter and leakage to the face. N95 respirator (in Europe disposable particulate respirator FFP2) have a minimum of 94% filtration percentage and maximum 8% leakage to the inside. As a standard, insulating respirators are most used (the filtering consists of a facepiece and a filtering device, sometimes with an exhalation valve).

According to CDC “The ‘N95’ designation means that when subjected to careful testing, the respirator blocks at least 95 percent of very small (0.3 micron) test particles.” Each SARS-CoV-2 virion is approximately 50–200 nanometers in diameter. 50-200 nanometer is 0.05- 0.2 microns. It means that N95 cannot prevent SARS-CoV-2 virus transmission.  However, the virus is not “naked”. It travels in mucus droplets and droplet nuclei, which are the dried-out residual of droplets presumably containing SARS-CoV-2 viruses. Mucus is of 95% water.

Again, an effective N95 respirator is designed to achieve a very close facial fit (8% leakage). Never mind that it is not achievable in hairy face.

Now, I want to address a significant, in my view, detail in using N95 respirator for individual’s protection from viruses in the air space which is in the person’s proximity. Otherwise, why bother to use a respirator.

The respirator catches droplets (>5 micro) and containing viruses droplet nuclei (≤5 micron) at the protected area in the same amount as at all other areas of the face, including adjacent to the respirator’s edges. While at the nose area the respirator is sealed by a metallic insert, the rest has certain narrow (8% leakage space between the face and the edges).

The droplet nuclei are water substances moving in the air, like fog, which is condensed water droplets. For understanding what is occurring in the narrow area (8% leakage) between the respirator’s edges the face, we need to apply some physics, particularly the Bernoulli principle.

When a fluid flows into a narrower channel, its speed increases (Bernoulli principle). With a higher pressure on the outside, the high-velocity fluid forces other fluids into the stream. This process is called entrainment. An aspirator uses a high-speed stream of water to create a region of lower pressure. A paint or perfume sprayers, a carburetor or a chimney are examples.

The kinetic energy of the droplets flow is generated by the gradient between air pressure outside the respirator and the negative pressure of the person’s inhalation. Dust or other firm particle would stop by friction.  Their form is certain. The droplet nuclei is water. It can change its form. It sneaks inside the respirator without opportunity to go out because the exhale is passive. The number of sneaked droplet nuclei is minimal, but a person is breathing around 15-18 times per hour. The wet and warm mask provides the virus in droplets comfortable dwelling. The mask becomes a hotbed for viruses. The droplet nuclei viruses content can go without any difficulty in the” infection gates” as nose and mouth.  

In a case of a mask similar to regular surgical mask, there is an air flow around the mask’s edges without forcible entrainment. Designed for preventing firm particles inhalation, the N95 respirator without 100% face fit, which is practically impossible, is, in my view, unacceptable for biological object like SARS-CoV-2 virus. I would appreciate any substantial objections to these considerations.

Additional problem of a regular N95 respirator is dome like relatively firm design.  By a person’s exhale, the respirator accumulates on its wet and warm outside surface droplet nuclei with viruses, if they supposedly exist. They can dwell there comfortably until the respirator is taken off. However, the protective device should be taken off by slow careful rolling keeping the external surface inside the roll. This is difficult by the respirators form and fabric. Those are not unimportant details. The infectious material in semi-dried droplets appears in relatively large quantities directly in the areas most vulnerable for the entry during the taken off the respirator.

Other protective masks

As a practical solution, in my view, would be either complete sealing as Figures A and B or the Kimberly- Clark FLUIDSHIELD mask type with (better) or without shield.

Kimberly- Clark FLUIDSHIELD mask has five layers. Both the internal and external (orange stripes) layers are water permeable. The three layers between them have different degrees of water resistance. Although the company advertises them as LONCET breathable film, these layers, in my experience, make the mask uncomfortable for prolonged use because the area between the mask and the face is overheated and over-saturated with exhaled carbon dioxide that decreases the percentage of oxygen in the inhaled air.

Kimberly- Clark FLUIDSHIELD mask. 

Protective Face Shield Visor, like offered by Htovila or Decdeal, is seemingly convenient. It definitely protects from dust and splashes and other situations of direct infectious material application. But it does not substitute the mask which it is necessary as protection from airborne infectious material, like coronaviruses. PET (polyester) material is relatively rigid and difficult to adjust to the protective gown for the neck protection. In my opinion, and experience of working with different masks, the Kimberly- Clark FLUIDSHIELD mask upside down (see above) wearing is preferable.

Decdeal Safety Face Shield

3M™ Full Facepiece Respirator 7800 Series looks solid, though intimidating, but it does not solve the main problem of the standard N95 respirator, namely face-fit adjustment that in the case of protection from viruses in crucial. Some suggestion to use this devise with reusable filter is controversial. In my view, it is unadvisable under condition of COVID-19 epidemic.

3M™ Full Facepiece Respirator 7800 Series

The development of protective mask will continue. Hopefully, the inventors would not think that the SARS-CoV-2 virus is going to reach specifically a cupper insert to be destroyed.

Meanwhile, if people feel comfortable by using a mask, let them do it, including bringing some creativity and fun, like the mask with owls on it. Positive spirit is part of healing from real dangers and unsubstantiated fears.

However, bandanas (bandannas) and similar creative protection “devices” are not innocent from infectious epidemiology point. We are not at the masquerade. This issues will be discussed in a special post later.

The main thing is that manufacturers understand design principles of a protective mask against the airborne infection. And the mask is correctly used. Both posts are written on the background of my experience in anatomic pathology as a pathologist, pathologists’ assistant, morgue attended, and grossing technologist.

Protective Face Covering Folly

From Chicago area food market store email (italics and bold added):

Shop and Save Market no-reply@shopandsavemarket.com Wed 4/22/2020 3:00 PM Face Mask Required Effective April 22nd,                                               Dear Customers, We respectfully request that you wear a protective face covering when shopping with us. For your and our safety & protection. Mask, Homemade Mask, Bandana or Scarf.

For your safety & protection

If a person is surrounded by SARS-CoV-2 virus in a given place, otherwise a protective face covering for you is not needed, viruses are disseminated equally around the head and neck areas at least. Even when virus’s carrier sneezes in close proximity at the person wearing a bandana.

The droplet nuclei (containing the viable viruses, in sneezing 40 million, in coughing only 5 million) do not have any knowledge where the “infection gates” (nose, mouth, eye conjunctive) are. Droplet nuclei land indiscriminately on every place. However, a mask, bandana or scarf provide them conditions in maintaining their comfortable dwelling by warm and wet person’s breath. Although the forehead or the neck might be sweaty, at these places and especially on the cloth viruses are less viable by losing their water surrounding.

The protective mask becomes a hub for viable viruses. The face cover should be treated as biohazard material. Are these masks taken off according to infectious epidemiology rules avoiding contamination of hands, face, and cloth? Are they disposable? More than likely not. How are they discarded? And numerous additional epidemiology questions.

For our safety & protection

Apparently, this is about preventing SARS-CoV-2 virus contamination the indoor space. Face covering to protect others from the potential carrier of viruses could be rational if a symptomatic people come in droves to the enclosed public spaces and sneeze and cough out their infectious material. This is very much questionable now. Asymptomatic viruses’ carriers distribute them without sneezing and coughing. Workers, who perform in-person jobs, now have separating from public plastic screens and use non-medical grade face coverings.


Nasopharyngeal area is one of the first lines of defense in the fight with a virus, which includes the initial cellular immunologic response. This defensive zone is the product and gift of humans evolution. The face covering does not contribute to its effective function. I know this as a person who worked many hours using a protective personal equipment mask.

In contrast to (PPE), which is a necessity under certain conditions for medical and other professionals, in my definite believe, the face covering in public space indoors and definitely outdoors is not only unnecessary but wrong under COVID-19 epidemic.   

Compulsory Protective Masks

On April 24th, Michigan Governor Gretchen Whitmer signed EXECUTIVE ORDER No. 2020-59 Temporary requirement to suspend activities that are not necessary to sustain or protect life. The current post discussed only the point 15, which is related to mandatory protective face covering.

15. Effective on April 26, 2020 at 11:59 pm:

(a) Any individual able to medically tolerate a face covering must wear a covering over his or her nose and mouth—such as a homemade mask, scarf, bandana, or handkerchief—when in any enclosed public space.

(b) All businesses and operations whose workers perform in-person work must, at a minimum, provide non-medical grade face coverings to their workers. (bold added)

The purpose of this order is in protecting people of Michigan from you, the suspect of SARS-CoV-2 virus carrier. You, perhaps intentionally through sneezing or coughing, or even unintentionally being asymptomatic would contaminate any enclosed public space, especially “workers perform in-person work.” Never mind that according to point (b) All businesses and operations whose workers perform in-person work must, at a minimum, provide non-medical grade face coverings to their workers (italics and bold added). Scared by the death toll in Detroit, people are of each other more than 6 feet because they don’t carry a yardstick to measure the safe distance.

The Governor’s order obliges me to wear a mask which is, in my believe, a danger to me and others under current conditions. I can defend the notion that wearing masks in public life, including enclosed public space, is founded on unsubstantiated premises (see three previous post on this subject).

COVID-19 epidemic generated a commonly accepted by public notion regarding wearing a protection mask. It is based on a natural instinct to cover the “infection gates”, understandable to everyone, relatively cheap, easily achievable, psychologically acceptable. Even Surgeon General Dr. Jerome Adams could show how to do a mask at home. Although when he took from his pocket a mask at the White House briefing, he demonstrated his innocence in following epidemiology rules.

Here is an excerpt from on of the most reputed journal in internal medicine (bold added). New England Journal of Medicine  on  May 21, 2020 Perspective Universal Masking in Hospitals in the Covid-19 Era

Michael Klompas, M.D., M.P.H., Charles A. Morris, M.D., M.P.H., Julia Sinclair, M.B.A., Madelyn Pearson, D.N.P., R.N., and Erica S. Shenoy, M.D., Ph.D.

“We know that wearing a mask outside health care facilities offers little, if any, protection from infection. Public health authorities define a significant exposure to Covid-19 as face-to-face contact within 6 feet with a patient with symptomatic Covid-19 that is sustained for at least a few minutes (and some say more than 10 minutes or even 30 minutes). The chance of catching Covid-19 from a passing interaction in a public space is therefore minimal. In many cases, the desire for widespread masking is a reflexive reaction to anxiety over the pandemic.”

However, when the hyperactive authorities impose as mandatory scientifically unproved and epidemiologically wrong action on the general public, it is not good. This order looks as a politically motivated action to impose more and more control upon society.

The next will be obligatory testing (this issue I’m going to explore in a serial next posts). The rationality of seatbelts or helmets were proved. Mandatory masks in enclosed public space open the window for other restrictions in public life with questionable premises. They will gradually crawl in. Do we want to live in China or even in splendid, almost sterile Singapore?  Yes, almost everyone is wearing a mask outdoors in Japan, but a mask is not out of their culture conscience.  

Independently where the Wuhan virus came from, now poor, hated by everyone SARS-CoV-2 virus is a part of the environment with the same rights as mosquitos, elephants, and humans. A crazy question about protective masks use. Would not be right for humans to join Saints Indians who cover their mouth with a cloth (Muhapatti) that prevents them from swallow by accident a mosquito?

Silly humor in gray times, when for political gains, a Russian roulette is played in the uncertainty casino. Political weaponization of a medical crisis is suicidal for democracy and for the society eventually.

This post is the last of four previous on the masks subject.  The goal was bringing some rationality in their use by distinguish masks as a part of protective equipment for professional and just protective face covering. The main focus was to make a dent in protective face covering understanding which is at the level of delusion, unhealthy for an individual and the society.

ICD-10 code for COVID-19

The correct medical statistics is crucial during an epidemic. The mortality data are particularly significant during COVID-19 because it is one of the unusual signs of this epidemic.           

National Vital Statistic System (NVSS) issues COVID-19 Alert No. 2 letter on March 24, 2020 that “a newly-introduced ICD code has been implemented to accurately capture mortality data for Coronavirus Disease 2019 (COVID-19) on death certificates.” “The new ICD code for Coronavirus Disease 2019 (COVID-19) is U07.1.”

The letter includes also a puzzling paragraph: “The WHO [World Health Organization] has provided a second code, U07.2, for clinical or epidemiological diagnosis of COVID-19 where a laboratory confirmation is inconclusive or not available. Because laboratory test results are not typically reported on death certificates in the U.S., NCHS [National Center for Health Statistics] is not planning to implement U07.2 for mortality statistics”. (Bold and [ ] brackets added).

Epidemiological diagnosis exists only in WHO’s heads. There are clinical and post mortem/autopsy diagnoses. The latter is not mentioned at all. Clinical and autopsy diagnoses can be a source for the epidemiological assessment but not otherwise. So called, epidemiological diagnosis makes mortality rate more discretional and to some degree inflate the numbers of death during COVID-19. The last thing that we need in this coronavirus pandemic which is accompanied by an epidemic of fear.

The World Health Organization allowed China (the second after USA donor) to hide real the COVID-19 outbreak’s numbers in December-January. The cavalierly approach to death statistics is not helpful, moreover counterproductive.

Excerpt from Center for Disease Control and Prevention (CDC) official document on COVID-19


The CDC 2019-Novel Coronavirus (2019-nCoV) Real-Time RT-PCR Diagnostic Panel is a real-time RT-PCR test intended for the qualitative detection of nucleic acid from the 2019-nCoV in upper and lower respiratory specimens (such as nasopharyngeal or oropharyngeal swabs, sputum, lower respiratory tract aspirates, bronchoalveolar lavage, and nasopharyngeal wash/aspirate or nasal aspirate) collected from individuals who meet 2019-nCoV clinical and/or epidemiological criteria (for example, clinical signs and symptoms (the difference between signs and symptoms?) associated with 2019-nCoV infection, contact with a probable or confirmed 2019-nCoV case, history of travel to geographic locations where 2019-nCoV cases were detected (except Antarctica and Arctica in the pandemia?) , or other epidemiologic links (couple examples ?) for which 2019-nCoV testing may be indicated as part of a public health investigation). Testing in the United States is limited to laboratories certified under the Clinical Laboratory Improvement Amendments of 1988 (CLIA), 42 U.S.C. § 263a, to perform high complexity tests. Results are for the identification of 2019-nCoV RNA. The 2019-nCoV RNA is generally detectable in upper and lower respiratory specimens during infection. Positive results are indicative of active infection with 2019-nCoV but do not rule out bacterial infection or co-infection with other viruses. The agent detected may not be the definite cause of disease. Laboratories within the United States and its territories are required to report all positive results to the appropriate public health authorities. Negative results do not preclude 2019-nCoV infection and should not be used as the sole basis for treatment or other patient management decisions. Negative results must be combined with clinical observations, patient history, and epidemiological information.

Bold, italics, and question mark are mine.

Many question marks are in the CDC official document. When the notion of testing, testing, testing became one of the main ways of solving the COVID-19 epidemic, the information of positive or negative 2019-nCoV tests reliability is essential. CDC ought to provide this information without hiding behind general statement.