CDC removes guidance saying coronavirus spreads through air – Washington Examiner

The CDC has long maintained that the coronavirus is transmitted through droplets spread among people in close proximity to one another. On Friday, it updated its guidelines, adding that the virus also spreads through “respiratory droplets or small particles, such as those in aerosols, produced when an infected person coughs, sneezes, sings, talks, or breathes,” adding that this is the main vector of infection.

The guidance no longer says COVID-19 can be spread through the air, and the agency said it will update the language once its review process “has been completed.”


COVID-19 – research evidence summaries – Royal College of Paediatrics and Child Health

Are children as likely as adults to acquire COVID-19?

Emerging evidence suggests that children may be less likely to acquire the disease. This is supported in countries that have undertaken widespread community testing, where lower case numbers in children than adults have been found.4 14 44 45 Between 16 January and 3 May 2020, 35,200 children in England were swabbed for SARS-CoV-2 and 1408 (4%) were positive. Children under 16 years old accounted for only 1.1% of positive cases.

Can children transmit the virus?

The importance of children in transmitting the virus is difficult to establish, particularly because of the number of asymptomatic cases, but there is some evidence that their role in transmitting the virus is limited…


Primary schools ‘no greater risk than home’ for pupils and staff – BBC

Attending primary school puts children and staff at no greater risk of contracting coronavirus than staying at home, a study of 131 schools suggests…

…A separate sample of 2,100 staff and children, who were tested for antibodies, found 10.6% of pupils and 12.7% of staff had previously had coronavirus.

This could suggest that children are as likely as adults to be infected, rather than being less susceptible to the disease.

But because so few positive cases in children are detected, it confirms previous research that they are likely to experience mild symptoms, or none at all.

The study found children and staff who attended school more frequently were no more likely to test positive for antibodies than those who did not attend school, or went less often.

News Opinion

The Case Against Covid Tests for the Young and Healthy – Wall Street Journal

There is little purpose in using tests to check asymptomatic children to see if it is safe for them to come to school. When children are infected, most are asymptomatic, and the mortality risk is lower than for the flu. While adult-to-adult and adult-to-child transmission is common, child-to-adult transmission isn’t. Children thus pose minimal risk to their teachers. If a child has a cough, a runny nose or other respiratory symptoms, he should stay home. You don’t need a test for that.

Sweden was the only major Western country that kept schools open for kids 15 and younger throughout the pandemic, with no masks or mass testing. How did it turn out? Zero Covid-19 deaths among 1.8 million children attending day care or school. Teachers didn’t have an excess infection risk compared with the average of other professions.

News Opinion

The Failed Experiment of Covid Lockdowns – Wall Street Journal

New data shows that ockdowns correlated with a greater spread of the virus.

Six months into the Covid-19 pandemic, the U.S. has now carried out two large-scale experiments in public health—first, in March and April, the lockdown of the economy to arrest the spread of the virus, and second, since mid-April, the reopening of the economy. The results are in. Counterintuitive though it may be, statistical analysis shows that locking down the economy didn’t contain the disease’s spread and reopening it didn’t unleash a second wave of infections.

Considering that lockdowns are economically costly and create well-documented long-term public-health consequences beyond Covid, imposing them appears to have been a large policy error. At the beginning, when little was known, officials acted in ways they thought prudent. But now evidence proves that lockdowns were an expensive treatment with serious side effects and no benefit to society…

Measuring from the start of the year to each state’s point of maximum lockdown—which range from April 5 to April 18—it turns out that lockdowns correlated with a greater spread of the virus. States with longer, stricter lockdowns also had larger Covid outbreaks. The five places with the harshest lockdowns—the District of Columbia, New York, Michigan, New Jersey and Massachusetts—had the heaviest caseloads.

News Opinion

Children could spread COVID19 more if they wear masks – Professor Russell Viner, BBC Newsnight

According to professor Russell Viner, President of Royal College of Paediatrics and SAGE member:

  • There’s very little evidence for the use of masks in schools.
  • Children could potentially spread the virus more if they wear masks

Pupils pose no risk of spreading Covid – Professor Russell Viner, The Sunday Times

One of the largest studies in the world on coronavirus in schools, carried out in 100 institutions in the UK, will confirm that “there is very little evidence that the virus is transmitted” there, according to a leading scientist.

Professor Russell Viner, president of the Royal College of Paediatrics and Child Health and a member of the government advisory group Sage, said: “A new study that has been done in UK schools confirms there is very little evidence that the virus is transmitted in schools.

“This is the some of the largest data you will find on schools anywhere. Britain has done very well in terms of thinking of collecting data in schools.”


No known case of teacher catching coronavirus from pupils, says scientist – The Times

There has been no recorded case of a teacher catching the coronavirus from a pupil anywhere in the world, according to one of the government’s leading scientific advisers.

Mark Woolhouse, a leading epidemiologist and member of the government’s Sage committee, told The Times that it may have been a mistake to close schools in March given the limited role children play in spreading the virus.


Keeping schools open had no impact on contagion, Swedish study suggests – The Telegraph

Shutting down primary schools may have been unnecessary as a Swedish study suggests that keeping them open had no impact on contagion.

There was no measurable difference in the number of coronavirus cases among children in Sweden, where schools were left open, compared with neighboring Finland, where schools were shut, the research showed.

A working paper, published by the Public Health Agency of Sweden and the Finnish Institute for Health and Welfare, compares the two countries’ approach to education during the pandemic.

Visitor Contributions

Covid 19 X-Factor in Spain – Nursing Homes: UNDERSTANDING WHAT REALLY HAPPENED

In the interest of public debate, we allow visitors to share opinions, experiences and research that may be of value to others. This is a visitor contribution from our Discussions page.

The views expressed are those of the individual posters themselves. Please read our Comments and contributions disclaimer.


Alfonso Longo

Covid 19 X-Factor in Spain – Nursing Homes: UNDERSTANDING WHAT REALLY HAPPENED


The nursing homes, their structure and management, explain the impact of the covid-19 pandemic in Spain.

DIRECTLY: because of the weight of its mortality

CAUSALLY: because of its effect on the transmission of the virus to the rest of the population

Therefore, in order to minimize the impact of covid on society, its impact on nursing homes must first be minimized.

Download the document here.

(Note that the document is hosted on Google Drive.)


Advice on the use of masks in the context of COVID-19 – WHO


According to the current evidence, COVID-19 virus is primarily transmitted between people via respiratory droplets and contact routes. Droplet transmission occurs when a person is in close contact (within 1 metre) with an infected person and exposure to potentially infective respiratory droplets occurs.

N95 vs medical masks:

Meta-analyses in systematic literature reviews have reported that the use of N95 respirators compared with the use of medical masks is not associated with any statistically significant lower risk of the clinical respiratory illness outcomes or laboratory-confirmed influenza or viral infections.

Wearing masks by the general public:

There is limited evidence that wearing a medical mask by healthy individuals in households, in particular those who share a house with a sick person, or among attendees of mass gatherings may be beneficial as a measure preventing transmission.

At present, there is no direct evidence (from studies on COVID-19 and in healthy people in the community) on the effectiveness of universal masking of healthy people in the community to prevent infection with respiratory viruses, including COVID-19.

At the present time, the widespread use of masks by healthy people in the community setting is not yet supported by high quality or direct scientific evidence and there are potential benefits and harms to consider.


Limited evidence regarding the respiratory protection using non-medical / homemade masks – SAGE

SARS-CoV-2 in the hospital environment and risk of COVID-19 nosocomial transmission

A document produced by SAGE states the following.

Evidence on efficacy of cloth face-coverings (non-medical masks):

There is limited evidence regarding the respiratory protection that non-medical / homemade masks can offer for the wearer, and there are no established quality standards for self-made face masks. One study reported a low filter efficiency (3-33%), and high penetration (up to 97%) of NaCl aerosol particles in homemade masks (42). A trial comparing the use of cloth and medical masks by healthcare workers also showed penetration of microorganisms by 97%, compared with a rate of 44% for medical masks (43).


Coronavirus: Why everyone was wrong – Dr. Beda Stadler

Professor Dr. Beda M Stadler is the former director of the Institute for Immunology at the University of Bern, a biologist and professor emeritus.


Sars-Cov-2 isn’t all that new, but merely a seasonal cold virus that mutated and disappears in summer, as all cold viri do — which is what we’re observing globally right now. Flu viri mutate significantly more, by the way, and nobody would ever claim that a new flu virus strain was completely novel.


In mid-April work was published by the group of Andreas Thiel at the Charité Berlin. A paper with 30 authors, amongst them the virologist Christian Drosten. It showed that in 34 % of people in Berlin who had never been in contact with the Sars-CoV-2 virus showed nonetheless T-cell immunity against it (T-cell immunity is a different kind of immune reaction, see below). This means that our T-cells, i.e. white blood cells, detect common structures appearing on Sars-CoV-2 and regular cold viri and therefore combat both of them.

…almost no children under ten years old got sick, everyone should have made the argument that children clearly have to be immune. For every other disease that doesn’t afflict a certain group of people, we would come to the conclusion that that group is immune. When people are sadly dying in a retirement home, but in the same place other pensioners with the same risk factors are left entirely unharmed, we should also conclude that they were presumably immune.


Epidemiologist also fell for the myth that there was no immunity in the population. They also didn’t want to believe that coronaviri were seasonal cold viri that would disappear in summer. Otherwise their curve models would have looked differently. When the initial worst case scenarios didn’t come true anywhere, some now still cling to models predicting a second wave.

Asymptomatic transmission:

The term “silent carriers” was conjured out of a hat and it was claimed that one could be sick without having symptoms.

The next joke that some virologists shared was the claim that those who were sick without symptoms could still spread the virus to other people…But for doctors and virologists to twist this into a story of “healthy” sick people, which stokes panic and was often given as a reason for stricter lockdown measures, just shows how bad the joke really is. At least the WHO didn’t accept the claim of asymptomatic infections and even challenges this claim on its website.


So if we do a PCR corona test on an immune person, it is not a virus that is detected, but a small shattered part of the viral genome. The test comes back positive for as long as there are tiny shattered parts of the virus left. Correct: Even if the infectious viri are long dead, a corona test can come back positive, because the PCR method multiplies even a tiny fraction of the viral genetic material enough [to be detected]…The crux was that the virus debris registered with the overly sensitive test and therefore came back as “positive”. It is likely that a large number of the daily reported infection numbers are purely due to viral debris.

Kawasaki Syndrome:

If an infected person does not have enough antibodies, i.e. a weak immune response, the virus slowly spreads out across the entire body. Now that there are not enough antibodies, there is only the second, supporting leg of our immune response left: The T-cells beginn to attack the virus-infested cells all over the body. This can lead to an exaggerated immune response, basically to a massive slaughter; this is called a Cytokine Storm. Very rarely this can also happen in small children, in that case called Kawasaki Syndrome. This very rare occurrence in children was also used in our country to stoke panic. It’s interesting, however, that this syndrome is very easily cured. The [affected] children get antibodies from healthy blood donors, i.e. people who went through coronavirus colds.

Second Wave:

The virus is gone for now. It will probably come back in winter, but it won’t be a second wave, but just a cold.

Face masks:

Those young and healthy people who currently walk around with a mask on their faces would be better off wearing a helmet instead, because the risk of something falling on their head is greater than that of getting a serious case of Covid-19.


People below 65 years old make up only 0.6 to 2.6 % of all fatal Covid cases. To get on top of the pandemic, we need a strategy merely concentrating on the protection of at-risk people over 65.


Why Face Masks Don’t Work: A Revealing Review – John Hardie, PhD, Oral Health Group (2016)

Note: This article, published on 16 October 2016, originally appeared in the Oral Health website. It was removed sometime after the end of June 2020 with no explanation other than, it being ‘no longer relevant in our current climate.’

The science behind face masks has not changed considerably in the past few months so we can only guess about what ‘no longer relevant’ means.

While you can find a capture at, we have saved a copy here to protect against censorship and for easy sharing.

Yesterday’s Scientific Dogma is Today’s Discarded Fable

The above quotation is ascribed to Justice Archie Campbell author of Canada’s SARS Commission Final Report. 1 It is a stark reminder that scientific knowledge is constantly changing as new discoveries contradict established beliefs. For at least three decades a face mask has been deemed an essential component of the personal protective equipment worn by dental personnel. A current article, “Face Mask Performance: Are You Protected” gives the impression that masks are capable of providing an acceptable level of protection from airborne pathogens. 2 Studies of recent diseases such as Severe Acute Respiratory Syndrome (SARS), Middle Eastern Respiratory Syndrome (MERS) and the Ebola Crisis combined with those of seasonal influenza and drug resistant tuberculosis have promoted a better understanding of how respiratory diseases are transmitted. Concurrently, with this appreciation, there have been a number of clinical investigations into the efficacy of protective devices such as face masks. This article will describe how the findings of such studies lead to a rethinking of the benefits of wearing a mask during the practice of dentistry. It will begin by describing new concepts relating to infection control especially personal protective equipment (PPE).

Trends in Infection Control
For the past three decades there has been minimal opposition to what have become seemingly established and accepted infection control recommendations. In 2009, infection control specialist Dr. D. Diekema questioned the validity of these by asking what actual, front-line hospital-based infection control experiences were available to such authoritative organization as the Centers for Disease Control and Prevention (CDC), the Occupational Safety and Health Association (OSHA) and the National Institute for Occupational Safety and Health (NIOSH). 3 In the same year, while commenting on guidelines for face masks, Dr. M. Rupp of the Society for Healthcare Epidemiology of America noted that some of the practices relating to infection control that have been in place for decades, ”haven’t been subjected to the same strenuous investigation that, for instance, a new medicine might be subjected.” 4 He opined that perhaps it is the relative cheapness and apparent safety of face masks that has prevented them from undergoing the extensive studies that should be required for any quality improvement device. 4 More recently, Dr. R. MacIntyre, a prolific investigator of face masks, has forcefully stated that the historical reliance on theoretical assumptions for recommending PPEs should be replaced by rigorously acquired clinical data. 5 She noted that most studies on face masks have been based on laboratory simulated tests which quite simply have limited clinical applicability as they cannot account for such human factors as compliance, coughing and talking. 5

Covering the nose and mouth for infection control started in the early 1900s when the German physician Carl Flugge discovered that exhaled droplets could transmit tuberculosis. 4 The science regarding the aerosol transmission of infectious diseases has, for years, been based on what is now appreciated to be “very outmoded research and an overly simplistic interpretation of the data.” 6 Modern studies are employing sensitive instruments and interpretative techniques to better understand the size and distribution of potentially infectious aerosol particles. 6 Such knowledge is paramount to appreciating the limitations of face masks. Nevertheless, it is the historical understanding of droplet and airborne transmission that has driven the longstanding and continuing tradition of mask wearing among health professionals. In 2014, the nursing profession was implored to “stop using practice interventions that are based on tradition” but instead adopt protocols that are based on critical evaluations of the available evidence. 7

A December 2015 article in the National Post seems to ascribe to Dr. Gardam, Director of Infection Prevention and Control, Toronto University Health Network the quote, “I need to choose which stupid, arbitrary infection control rules I’m going to push.” 8 In a communication with the author, Dr. Gardam explained that this was not a personal belief but that it did reflect the views of some infection control practitioners. In her 2014 article, “Germs and the Pseudoscience of Quality Improvement”, Dr. K Sibert, an anaesthetist with an interest in infection control, is of the opinion that many infection control rules are indeed arbitrary, not justified by the available evidence or subjected to controlled follow-up studies, but are devised, often under pressure, to give the appearance of doing something. 9

The above illustrate the developing concerns that many infection control measures have been adopted with minimal supporting evidence. To address this fault, the authors of a 2007 New England Journal of Medicine (NEJM) article eloquently argue that all safety and quality improvement recommendations must be subjected to the same rigorous testing as would any new clinical intervention. 10 Dr. R. MacIntyre, a proponent of this trend in infection control, has used her research findings to boldly state that, “it would not seem justifiable to ask healthcare workers to wear surgical masks.” 4 To understand this conclusion it is necessary to appreciate the current concepts relating to airborne transmissions.

Airborne Transmissions
Early studies of airborne transmissions were hampered by the fact that the investigators were not able to detect small particles (less than 5 microns) near an infectious person. 6 Thus, they assumed that it was the exposure of the face, eyes and nose to large particles (greater than 5 microns) or “droplets” that transmitted the respiratory condition to a person in close proximity to the host. 6 This became known as “droplet infection”, and 5 microns or greater became established as the size of large particles and the traditional belief that such particles could, in theory, be trapped by a face mask. 5 The early researchers concluded that since only large particles were detected near an infectious person any small particles would be transmitted via air currents, dispersed over long distances, remain infective over time and might be inhaled by persons who never had any close contact with the host. 11 This became known as “airborne transmission” against which a face mask would be of little use. 5

Through the use of highly sensitive instruments it is now appreciated that the aerosols transmitted from the respiratory tract due to coughing, sneezing, talking, exhalation and certain medical and dental procedures produce respiratory particles that range from the very small (less than 5 microns) to the very large (greater than a 100 microns) and that all of these particles are capable of being inhaled by persons close to the source. 6, 11 This means that respiratory aerosols potentially contain bacteria averaging in size from 1-10 microns and viruses ranging in size from 0.004 to 0.1 microns. 12 It is also acknowledged that upon their emission large “droplets” will undergo evaporation producing a concentration of readily inhalable small particles surrounding the aerosol source. 6

The historical terms “droplet infection” and “airborne transmission” defined the routes of infection based on particle size. Current knowledge suggests that these are redundant descriptions since aerosols contain a wide distribution of particle sizes and that they ought to be replaced by the term, “aerosol transmissible.” 4, 5 Aerosol transmission has been defined as “person –to – person transmission of pathogens through air by means of inhalation of infectious particles.” 26 In addition, it is appreciated that the physics associated with the production of the aerosols imparts energy to microbial suspensions facilitating their inhalation. 11

Traditionally face masks have been recommended to protect the mouth and nose from the “droplet” route of infection, presumably because they will prevent the inhalation of relatively large particles. 11 Their efficacy must be re-examined in light of the fact that aerosols contain particles many times smaller than 5 microns. Prior to this examination, it is pertinent to review the defence mechanism of the respiratory tract.

Respiratory System Defences
Comprehensive details on the defence mechanisms of the respiratory tract will not be discussed. Instead readers are reminded that; coughing, sneezing, nasal hairs, respiratory tract cilia, mucous producing lining cells and the phagocytic activity of alveolar macrophages provide protection against inhaled foreign bodies including fungi, bacteria and viruses. 13 Indeed, the pathogen laden aerosols produced by everyday talking and eating would have the potential to cause significant disease if it were not for these effective respiratory tract defences.

These defences contradict the recently published belief that dentally produced aerosols, “enter unprotected bronchioles and alveoli.” 2 A pertinent demonstration of the respiratory tract’s ability to resist disease is the finding that- compared to controls- dentists had significantly elevated levels of antibodies to influenza A and B and the respiratory syncytial virus. 14 Thus, while dentists had greater than normal exposure to these aerosol transmissible pathogens, their potential to cause disease was resisted by respiratory immunologic responses. Interestingly, the wearing of masks and eye glasses did not lessen the production of antibodies, thus reducing their significance as personal protective barriers. 14 Another example of the effectiveness of respiratory defences is that although exposed to more aerosol transmissible pathogens than the general population, Tokyo dentists have a significantly lower risk of dying from pneumonia and bronchitis. 15 The ability of a face mask to prevent the infectious risk potentially inherent in sprays of blood and saliva reaching the wearers mouth and nose is questionable since, before the advent of mask use, dentists were no more likely to die of infectious diseases than the general population. 16

The respiratory tract has efficient defence mechanisms. Unless face masks have the ability to either enhance or lessen the need for such natural defences, their use as protection against airborne pathogens must be questioned.

Face Masks
History: Cloth or cotton gauze masks have been used since the late 19th century to protect sterile fields from spit and mucous generated by the wearer. 5,17,18 A secondary function was to protect the mouth and nose of the wearer from the sprays and splashes of blood and body fluids created during surgery. 17 As noted above, in the early 20th century masks were used to trap infectious “droplets” expelled by the wearer thus possibly reducing disease transmission to others. 18 Since the mid-20th century until to-day, face masks have been increasingly used for entirely the opposite function: that is to prevent the wearer from inhaling respiratory pathogens. 5,20,21 Indeed, most current dental infection control recommendations insist that a face mask be worn, “as a key component of personal protection against airborne pathogens”. 2

Literature reviews have confirmed that wearing a mask during surgery has no impact whatsoever on wound infection rates during clean surgery. 22,23,24,25,26 A recent 2014 report states categorically that no clinical trials have ever shown that wearing a mask prevents contamination of surgical sites. 26 With their original purpose being highly questionable it should be no surprise that the ability of face masks to act as respiratory protective devices is now the subject of intense scrutiny. 27 Appreciating the reasons for this, requires an understanding of the structure, fit and filtering capacity of face masks.

Structure and Fit: Disposable face masks usually consist of three to four layers of flat non-woven mats of fine fibres separated by one or two polypropylene barrier layers which act as filters capable of trapping material greater than 1 micron in diameter. 18,24,28 Masks are placed over the nose and mouth and secured by straps usually placed behind the head and neck. 21 No matter how well a mask conforms to the shape of a person’s face, it is not designed to create an air tight seal around the face. Masks will always fit fairly loosely with considerable gaps along the cheeks, around the bridge of the nose and along the bottom edge of the mask below the chin. 21 These gaps do not provide adequate protection as they permit the passage of air and aerosols when the wearer inhales. 11,17 It is important to appreciate that if masks contained filters capable of trapping viruses, the peripheral gaps around the masks would continue to permit the inhalation of unfiltered air and aerosols. 11

Filtering Capacity: The filters in masks do not act as sieves by trapping particles greater than a specific size while allowing smaller particles to pass through. 18 Instead the dynamics of aerosolized particles and their molecular attraction to filter fibres are such that at a certain range of sizes both large and small particles will penetrate through a face mask. 18 Accordingly, it should be no surprise that a study of eight brands of face masks found that they did not filter out 20-100% of particles varying in size from 0.1 to 4.0 microns. 21 Another investigation showed penetration ranges from 5-100% when masks were challenged with relatively large 1.0 micron particles. 29 A further study found that masks were incapable of filtering out 80-85% of particles varying in size from 0.3 to 2.0 microns. 30 A 2008 investigation identified the poor filtering performance of dental masks. 27 It should be concluded from these and similar studies that the filter material of face masks does not retain or filter out viruses or other submicron particles. 11,31 When this understanding is combined with the poor fit of masks, it is readily appreciated that neither the filter performance nor the facial fit characteristics of face masks qualify them as being devices which protect against respiratory infections. 27 Despite this determination the performance of masks against certain criteria has been used to justify their effectiveness.2 Accordingly, it is appropriate to review the limitations of these performance standards.

Performance Standards: Face masks are not subject to any regulations. 11 The USA Federal Food and Drug Administration (FDA) classifies face masks as Class II devices. To obtain the necessary approval to sell masks all that a manufacturer need do is satisfy the FDA that any new device is substantially the same as any mask currently available for sale. 21 As ironically noted by the Occupational Health and Safety Agency for Healthcare in BC, “There is no specific requirement to prove that the existing masks are effective and there is no standard test or set of data required supporting the assertion of equivalence. Nor does the FDA conduct or sponsor testing of surgical masks.” 21 Although the FDA recommends two filter efficiency tests; particulate filtration efficiency (PFE) and bacterial filtration efficiency (BFE) it does not stipulate a minimum level of filter performance for these tests. 27 The PFE test is a basis for comparing the efficiency of face masks when exposed to aerosol particle sizes between 0.1 and 5.0 microns. The test does not assess the effectiveness of a mask in preventing the ingress of potentially harmful particles nor can it be used to characterize the protective nature of a mask. 32 The BFE test is a measure of a mask’s ability to provide protection from large particles expelled by the wearer. It does not provide an assessment of a mask’s ability to protect the wearer. 17 Although these tests are conducted under the auspices of the American Society of Testing and Materials (ASTM) and often produce filtration efficiencies in the range of 95-98 %, they are not a measure of a masks ability to protect against respiratory pathogens. Failure to appreciate the limitations of these tests combined with a reliance on the high filtration efficiencies reported by the manufacturers has, according to Healthcare in BC, “created an environment in which health care workers think they are more protected than they actually are.” 21 For dental personnel the protection sought is mainly from treatment induced aerosols.

Dental Aerosols
For approximately 40 years it has been known that dental restorative and especially ultrasonic scaling procedures produce aerosols containing not only blood and saliva but potentially pathogenic organisms. 33 The source of these organisms could be the oral cavities of patients and/or dental unit water lines. 34 Assessing the source and pathogenicity of these organisms has proven elusive as it is extremely difficult to culture bacteria especially anaerobes and viruses from dental aerosols. 34 Although there is no substantiated proof that dental aerosols are an infection control risk, it is a reasonable assumption that if pathogenic microbes are present at the treatment site they will become aerosolized and prone to inhalation by the clinician which a face mask will not prevent. As shown by the study of UK dentists, the inhalation resulted in the formation of appropriate antibodies to respiratory pathogens without overt signs and symptoms of respiratory distress. 14 This occurred whether masks were or were not worn. In a 2008 article, Dr. S. Harrel, of the Baylor College of Dentistry, is of the opinion that because there is a lack of epidemiologically detectable disease from the use of ultrasonic scalers, dental aerosols appear to have a low potential for transmitting disease but should not be ignored as a risk for disease transmission. 34 The most effective measures for reducing disease transmission from dental aerosols are pre-procedural rinses with mouthwashes such as chlorhexidine, large diameter high volume evacuators, and rubber dam whenever possible. 33 Face masks are not useful for this purpose, and Dr. Harrel believes that dental personnel have placed too great a reliance on their efficacy. 34 Perhaps this has occurred because dental regulatory agencies have failed to appreciate the increasing evidence on face mask inadequacies.

The Inadequacies
Between 2004 and 2016 at least a dozen research or review articles have been published on the inadequacies of face masks. 5,6,11,17,19,20,21,25,26,27,28,31 All agree that the poor facial fit and limited filtration characteristics of face masks make them unable to prevent the wearer inhaling airborne particles. In their well-referenced 2011 article on respiratory protection for healthcare workers, Drs. Harriman and Brosseau conclude that, “facemasks will not protect against the inhalation of aerosols.” 11 Following their 2015 literature review, Dr. Zhou and colleagues stated, “There is a lack of substantiated evidence to support claims that facemasks protect either patient or surgeon from infectious contamination.” 25 In the same year Dr. R. MacIntyre noted that randomized controlled trials of facemasks failed to prove their efficacy. 5 In August 2016 responding to a question on the protection from facemasks the Canadian Centre for Occupational Health and Safety replied:

  • The filter material of surgical masks does not retain or filter out submicron particles;
  • Surgical masks are not designed to eliminate air leakage around the edges;
  • Surgical masks do not protect the wearer from inhaling small particles that can remain airborne for long periods of time. 31

In 2015, Dr. Leonie Walker, Principal Researcher of the New Zealand Nurses Organization succinctly described- within a historical context – the inadequacies of facemasks, “Health care workers have long relied heavily on surgical masks to provide protection against influenza and other infections. Yet there are no convincing scientific data that support the effectiveness of masks for respiratory protection. The masks we use are not designed for such purposes, and when tested, they have proved to vary widely in filtration capability, allowing penetration of aerosol particles ranging from four to 90%.” 35

Face masks do not satisfy the criteria for effectiveness as described by Drs. Landefeld and Shojania in their NEJM article, “The Tension between Needing to Improve Care and Knowing How to Do It. 10 The authors declare that, “…recommending or mandating the widespread adoption of interventions to improve quality or safety requires rigorous testing to determine whether, how, and where the intervention is effective…” They stress the critical nature of this concept because, “…a number of widely promulgated interventions are likely to be wholly ineffective, even if they do not harm patients.” 10 A significant inadequacy of face masks is that they were mandated as an intervention based on an assumption rather than on appropriate testing.

The primary reason for mandating the wearing of face masks is to protect dental personnel from airborne pathogens. This review has established that face masks are incapable of providing such a level of protection. Unless the Centers for Disease Control and Prevention, national and provincial dental associations and regulatory agencies publically admit this fact, they will be guilty of perpetuating a myth which will be a disservice to the dental profession and its patients. It would be beneficial if, as a consequence of the review, all present infection control recommendations were subjected to the same rigorous testing as any new clinical intervention. Professional associations and governing bodies must ensure the clinical efficacy of quality improvement procedures prior to them being mandated. It is heartening to know that such a trend is gaining a momentum which might reveal the inadequacies of other long held dental infection control assumptions. Surely, the hallmark of a mature profession is one which permits new evidence to trump established beliefs. In 1910, Dr. C. Chapin, a public health pioneer, summarized this idea by stating, “We should not be ashamed to change our methods; rather, we should be ashamed not to do so.” 36 Until this occurs, as this review has revealed, dentists have nothing to fear by unmasking. OH

Oral Health welcomes this original article.

1. Ontario Ministry of Health and Long-term Care. SARS Commission-Spring of Fear: Final Report. Available at:
2. Molinari JA, Nelson P. Face Mask Performance: Are You Protected? Oral Health, March 2016.
3. Diekema D. Controversies in Hospital Infection Prevention, October, 2009.
4. Unmasking the Surgical Mask: Does It Really Work? Medpage Today, Infectious Disease, October, 2009.
5. MacIntyre CR, Chughtai AA. Facemasks for the prevention of infection in healthcare and community settings. BMJ 2015; 350:h694.
6. Brosseau LM, Jones R. Commentary: Health workers need optimal respiratory protection for Ebola. Center for Infectious Disease Research and Policy. September, 2014.
7. Clinical Habits Die Hard: Nursing Traditions Often Trump Evidence-Based Practice. Infection Control Today, April, 2014.
8. Landman K. Doctors, take off those dirty white coats. National Post, December 7, 2015.
9. Sibert K. Germs and the Pseudoscience of Quality Improvement. California Society of Anesthesiologists, December 8, 2014.
10. Auerbach AD, Landfeld CS, Shojania KG. The Tension between Needing to Improve Care and Knowing How to Do It. NEJM 2007; 357 (6):608-613.
11. Harriman KH, Brosseau LM. Controversy: Respiratory Protection for Healthcare Workers. April, 2011. Available at:
12. Bacteria and Viruses Issues. Water Quality Association, 2016. Available at:
13. Lechtzin N. Defense Mechanisms of the Respiratory System. Merck Manuals, Kenilworth, USA, 2016
14. Davies KJ, Herbert AM, Westmoreland D. Bagg J. Seroepidemiological study of respiratory virus infections among dental surgeons. Br Dent J. 1994; 176(7):262-265.
15.  Shimpo H, Yokoyama E, Tsurumaki K. Causes of death and life expectancies among dentists. Int Dent J 1998; 48(6):563-570.
16. Bureau of Economic Research and Statistics, Mortality of Dentists 1961-1966. JADA 1968; 76(4):831-834.
17. Respirators and Surgical Masks: A Comparison. 3 M Occupational Health and Environment Safety Division. Oct. 2009.
18. Brosseau L. N95 Respirators and Surgical Masks. Centers for Disease Control and Prevention. Oct. 2009.
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RELATED ARTICLE: Face Mask Performance: Are You Protected?


Vaccine professor at Oxford University says ‘little chance’ now of proving if it works – Professor Sarah Gilbert, The Mirror

A coronavirus vaccine professor at Oxford University says there is now ‘little chance’ of proving if it works due to low transmission rates in the UK.

Professor Sarah Gilbert, leading the University of Oxford vaccine trial, said that when Covid-19 transmission was high, lockdown was imposed to bring the rate down.

But since then rates have dropped, and the trial relies on a sufficient number of volunteers to have been exposed to the virus to see whether a vaccine protects them or not.


School Children Don’t Spread Coronavirus, French Study Shows – Bloomberg

Scientists at Institut Pasteur studied 1,340 people in Crepy-en-Valois, a town northeast of Paris that suffered an outbreak in February and March, including 510 students from six primary schools. They found three probable cases among kids that didn’t lead to more infections among other pupils or teachers.

The study confirms that children appear to show fewer telltale symptoms than adults and be less contagious, providing a justification for school reopenings in countries from Denmark to Switzerland. The researchers found that 61% of the parents of infected kids had the coronavirus, compared with about 7% of parents of healthy ones, suggesting it was the parents who had infected their offspring rather than the other way around.


Masks Don’t Work: A Review of Science Relevant to COVID-19 Social Policy – Denis Rancourt (PhD) The River Cities’ Reader

No RCT study with verified outcome shows a benefit for HCW or community members in households to wearing a mask or respirator. There is no such study. There are no exceptions.

Likewise, no study exists that shows a benefit from a broad policy to wear masks in public.

Furthermore, if there were any benefit to wearing a mask, because of the blocking power against droplets and aerosol particles, then there should be more benefit from wearing a respirator (N95) compared to a surgical mask, yet several large meta-analyses, and all the RCT, prove that there is no such relative benefit.

Regarding the aerosol mechanism of infectious disease transmission:

Mask stoppage efficiency and host inhalation are only half of the equation, however, because the minimal infective dose (MID) must also be considered. For example, if a large number of pathogen-laden particles must be delivered to the lung within a certain time for the illness to take hold, then partial blocking by any mask or cloth can be enough to make a significant difference.

On the other hand, if the MID is amply surpassed by the virions carried in a single aerosol particle able to evade mask-capture, then the mask is of no practical utility, which is the case.

[I]f anything gets through (and it always does, irrespective of the mask), then you are going to be infected. Masks cannot possibly work. It is not surprising, therefore, that no bias-free study has ever found a benefit from wearing a mask or respirator in this application.

Regarding minimal infective dose:

  • Most respiratory viruses are as infective in humans as in tissue culture having optimal laboratory susceptibility
  • It is believed that a single virion can be enough to induce illness in the host
  • The 50-percent probability MID (“TCID50”) has variably been found to be in the range 100−1000 virions
  • There are typically 10 to 3rd power − 10 to 7th power virions per aerolized influenza droplet with diameter 1 μm − 10 μm
  • The 50-percent probability MID easily fits into a single (one) aerolized droplet
  • For further background:
  • A classic description of dose-response assessment is provided by Haas (1993).
  • Zwart et al. (2009) provided the first laboratory proof, in a virus-insect system, that the action of a single virion can be sufficient to cause disease.
  • Baccam et al. (2006) calculated from empirical data that, with influenza A in humans,“we estimate that after a delay of ~6 h, infected cells begin producing influenza virus and continue to do so for ~5 h. The average lifetime of infected cells is ~11 h, and the half-life of free infectious virus is ~3 h. We calculated the [in-body] basic reproductive number, R0, which indicated that a single infected cell could produce ~22 new productive infections.”
  • Brooke et al. (2013) showed that, contrary to prior modeling assumptions, although not all influenza-A-infected cells in the human body produce infectious progeny (virions), nonetheless, 90 percent of infected cell are significantly impacted, rather than simply surviving unharmed.

Regarding tests for a wide-scale mask-wearing policy:

  • Any benefit from mask-wearing would have to be a small effect, since undetected in controlled experiments, which would be swamped by the larger effects, notably the large effect from changing atmospheric humidity.
  • Mask compliance and mask adjustment habits would be unknown.
  • Mask-wearing is associated (correlated) with several other health behaviors; see Wada (2012).
  • The results would not be transferable, because of differing cultural habits.
  • Compliance is achieved by fear, and individuals can habituate to fear-based propaganda, and can have disparate basic responses.
  • Monitoring and compliance measurement are near-impossible, and subject to large errors.
  • Self-reporting (such as in surveys) is notoriously biased, because individuals have the self-interested belief that their efforts are useful.
  • Progression of the epidemic is not verified with reliable tests on large population samples, and generally relies on non-representative hospital visits or admissions.
  • Several different pathogens (viruses and strains of viruses) causing respiratory illness generally act together, in the same population and/or in individuals, and are not resolved, while having different epidemiological characteristics.

Unanswered questions about mask-wearing:

  • Do used and loaded masks become sources of enhanced transmission, for the wearer and others?
  • Do masks become collectors and retainers of pathogens that the mask wearer would otherwise avoid when breathing without a mask?
  • Are large droplets captured by a mask atomized or aerolized into breathable components? Can virions escape an evaporating droplet stuck to a mask fiber?
  • What are the dangers of bacterial growth on a used and loaded mask?
  • How do pathogen-laden droplets interact with environmental dust and aerosols captured on the mask?
  • What are long-term health effects on HCW, such as headaches, arising from impeded breathing?
  • Are there negative social consequences to a masked society?
  • Are there negative psychological consequences to wearing a mask, as a fear-based behavioral modification?
  • What are the environmental consequences of mask manufacturing and disposal?
  • Do the masks shed fibers or substances that are harmful when inhaled?


Coronavirus: Under-20s half as likely to catch COVID-19, according to study – Sky News

Researchers found school closures had little effect on preventing coronavirus transmission compared to that of the flu.

Under-20s are half as likely to catch COVID-19 as over-20s, making school closures less effective at stopping the spread of the virus, a new scientific study has found.

Researchers at the London School of Hygiene and Tropical Medicine found that susceptibility to the coronavirus was low for younger people, before increasing around the age of 20.


WHO Says Covid-19 Asymptomatic Transmission Is Very Rare – WHO

Maria Van Kerkhove, head of the World Health Organization’s emerging diseases and zoonosis unit, says transmission of the coronavirus by people who aren’t showing symptoms is “very rare.” She spoke Monday at a briefing in Geneva.


Estimating the extent of asymptomatic COVID-19 and its potential for community transmission: systematic review and meta-analysis – medRxiv

Estimates of asymptomatic rate and transmission rate are vital parameters for modelling studies. Our estimates of the proportion of asymptomatic cases and their transmission rates suggest that asymptomatic spread is unlikely to be a major driver of clusters or community transmission of infection, but the extent for pre-symptomatic and minor symptomatic transmission remains unknown. Other unknowns include whether there is a difference in age (particularly children vs adults), sex and underlying comorbidities that differentiate asymptomatic from pre-symptomatic cases; development of long-term immunity; and whether asymptomatic cases take longer to develop active disease or remain silent.