The Failure To Acknowledge Airborne Transmission
How Public Health Got It Wrong
Paradigms in Science
I’d like to begin by quoting from the introduction of The Documentary Hypothesis by Umberto Cassuto:
A mature science, according to Kuhn’s hypothesis, is one in which there exists a dominant paradigm — a conceptual framework that informs the scientist of what to expect as he engages in his or her scientific inquiry. It delineates the parameters of what can and cannot be considered acceptable solutions to a problem. Only that which conforms to the paradigm is deemed true. The training of scientists consists of inculcating them with the tenets of the paradigm, the rules of the game, before they embark on their own research. To engage in “normal science” is to endeavor to tie up loose ends and adjust the paradigm to reality. Paradigms introduce a sociological factor into science. To practice science is to engage in the mysteries of the natural order not in unmediated fashion, but through the lens of the paradigm, itself a human construct. This dogmatic aspect determines who is considered “in” in the scientific community, and how is “out”.
The paradigm against airborne transmission caused physicists, engineers, chemists, occupational hygienists and indoor air quality researchers to be placed in the “out” group, while public health officials and infectious disease doctors were “in”.
They controlled the narrative, enforced disastrous policies and left us with a legacy of distrust in the medical community, widespread anti-vaccination sentiment and an unsolved crisis in indoor air quality.
Denial of Airborne Transmission from the Beginning
Right from the beginning of the COVID-19 pandemic, public health organizations stated that COVID-19 was not airborne and only transmits through droplets.
While the novel coronavirus began spreading widely through early 2020, the WHO held a press conference.
In the conference at 40:20, Dr. Tedros Adhanom Ghebreyesus, the Director-General of the WHO stated:
Ebola is lousy, this is airborne, corona is airborne
At 41:50, Dr. Mike Ryan wrote something on a pad of paper and whispered something to Dr. Tedros Adhanom Ghebreyesus. Looking at the video, what he wrote and whispered is possibly “We can’t say airborne”. At 46:23, Dr. Tedros Adhanom Ghebreyesus retracted his comment:
Sorry, I used the military word airborne. It meant [sic] to spread via droplets or respiratory transmission. Please take it that way, not the military language [laughs].
An infamous tweet over one month later made the WHO’s position on airborne transmission abundantly clear.
Needless to say, there was no evidence for this claim. They changed their position almost 2 years later that COVID can spread at both short-range and long-range airborne transmission.
As a typical example from the beginning of the COVID-19 pandemic, there was a super-spreader event in a South African hospital in which a single infector infected 119 people with COVID-19 and 15 of them died. The spread was attributed to surface transfer through stethoscopes, thermometers and BP cuffs and the publication completely ignored the possibility of airborne transmission. The story is told here.
What contributed to this mistake? Why did they get it so wrong? Why did it take them so long to retract?
How Respiratory Diseases Transmit
Before discussing the medical mistakes, it’s important to identify how respiratory diseases spread. The evidence is currently overwhelming that respiratory diseases are airborne. People emit respiratory particles when breathing, talking, sneezing or coughing. Small respiratory particles, called aerosols, can float through the air and also contain infectious pathogens. People get infected when a sufficient dose is inhaled. This is known by many names, including airborne transmission, aerosol transmission or inhalation transmission.
Larger particles can spray out of your mouth or nose and land on a susceptible person’s eyes, nose or mouth. This was known in the medical community as droplet transmission or large droplet transmission and erroneously believed to be the main mode of transmission for respiratory diseases. There is no direct evidence for this belief.
Bad Science
The fundamental problem was that the medical community did not understand how diseases are transmitted. The historical reasons were detailed in the publication: What were the historical reasons for the resistance to recognizing airborne transmission during the COVID-19 pandemic?
Briefly, it was historically believed that most diseases spread through the air in what was called miasma. Evidence began to accumulate that many diseases did not spread through the air. Cholera was found by John Snow to spread through water. Malaria was found to spread through mosquitoes. Puerperal fever was found by Semmelweiss to spread through direct contact by doctors transferring bacteria from their hands to women in childbirth. None of these spread through the air and a paradigm shift occurred where airborne disease transmission was considered to be rare.
This reliance on bad science allowed many myths to form about airborne transmission. Many of these myths were addressed in a publication Dismantling myths on the airborne transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Some of these include:
Growing Virus in Tissue Culture
It is very difficult to sample virus from the air and then grow it in tissue culture. Many in the medical community believed this indicates that airborne transmission is rare. However, this does not mean that the virus cannot spread through the air. It is much easier to sample virus through surfaces, even though risk of transmission through surfaces is much lower.
Size of Particles
Contrary to basic physics, the medical community believed (and many still believe) that aerosols are particles that are less than 5 μm.
This belief was clearly incorrect. Many types of particulate matter, which include dust and pollen can be 10 μm or larger. The actual cutoff is closer to 100 μm.
When combining this myth with the fact that it is difficult to sample live virus in these particles, it’s easy to believe that airborne transmission is rare. It has been reported that these myths were linked to the recommendation of 1–2 m social distancing which is insufficient to mitigate airborne transmission.
Short-Range Transmission
The medical community believed that short-range transmission was caused by large droplet transmission and long-range transmission was caused by airborne transmission. Combined with the fact that they contact traced people that were in short range of a susceptible person, so primarily found cases that were in short range, it appeared short range transmission was the dominant mode and consequently, large droplet transmission was the dominant mode.
There was no basis for this but nevertheless, this belief existed. For example, as argued in this publication:
Long-range aerosol transmission (traditionally known as airborne transmission) occurs situationally, under certain conditions such as prolonged exposure in enclosed spaces with inadequate ventilation.
Or as the British Columbia Provincial Health Officer Dr. Bonnie Henry said:
What we are not seeing is what we call traditional airborne transmission which is, sort of, colloquially, we say transmission around corners or through ventilation systems …
The medical community invented a poor definition of airborne transmission and then used that definition to deny airborne transmission for COVID-19.
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The truth is airborne transmission is the inhalation of infectious aerosols. It can happen at short-range, when sharing a room or long-range. Shared room transmission is extremely high risk in poorly ventilated spaces and does not fit into the short-range droplet model. Nevertheless, the medical community only defined airborne transmission as long-range transmission, like being in a room at different times or transmission through HVAC systems or air currents between rooms. Overall, this situation for transmission is much lower risk than short-range or shared room transmission.
Infectiousness
Doctors believed that airborne diseases spread to many more people than non-airborne diseases and COVID-19 did not spread to enough people to meet some arbitrary threshold they defined. Therefore, it could not have been airborne. This is argued here by a Canadian Infectious Disease doctor:
I think it is reassuring though that the WHO stance, the CDC stance are supported by the actual observation that this infection seems to spread mostly from one person to two to three other people in most of the studies, whereas airborne infections, when that’s the main mode of transmission, usually spreads to a much greater number of people, like 8–12…
Another Canadian Infectious Disease doctor made a similar claim here:
If this were usually, or most commonly transmitted by the airborne route, then we would know it by now…if we had an outbreak of measles and we spent [sic] non immune health care workers into those rooms wearing a mask, they spent an hour in the room they would all get infected.
This is incorrect. The mode of transmission and infectiousness of a disease are two separate properties.
Aerosol Generating Procedures
Aerosol generating procedures (AGPs) are a myth invented by the medical community. These procedures include the open suctioning of airways, intubation, extubation, bronchoscopy and manual ventilation among others. The premise is that airborne diseases spread through inhalation of infectious aerosols and some actions or procedures can generate more aerosols and increase the risk of airborne transmission, which is true. However, AGPs do not generate more aerosols than common actions like talking or singing. The medical community believed that diseases can be not airborne unless performing AGPs where they can become airborne. There was no evidence for this belief.
This was used as a basis to state that when performing AGPs, airborne precautions should be taken, like ensuring proper ventilation or using respirators. However, these precautions were ignored, discouraged or even prohibited when not performing AGPs. This was significant argument used to prohibit use of respirators or not needing improved ventilation in community settings.
The medical community still believes in AGPs. Any mention of AGPs by public health organizations attests to a refusal to accept evidence and cling to old dogma.
Precautionary Principle
Even if there was a bad understanding of how airborne transmission worked, it does not explain why the precautionary principle was ignored. Why didn’t public health assume that it might have been airborne and take reasonable precautions? Here are some reported reasons for ignoring the precautionary principle:
Medical Arrogance and Ignoring Other Professions
Possibly, the medical field were so absolutely confident in their paradigm, that they believed the precautionary principle didn’t apply.
Airborne transmission is fundamentally an air quality problem. Infectious pathogens in the air are an air pollutant, just like fine particulate matter, volatile organic compounds or radon. The method to mitigate harm from air pollutants is to lower the dose to acceptable levels by removing the pollutant from the air at an acceptable rate or preventing its introduction into the space.
A group of scientists led by Lidia Morawska called “Group 36” raised this issue with the WHO at the beginning of the pandemic. Unfortunately, they were not taken seriously. As they later recounted in the article Science Rejected, Lives Lost:
However, our voice was ignored by WHO at the beginning of the pandemic, which was the most critical time for action.
The real experts knew it was airborne, but the medical community ignored them and became the gatekeepers to prevent addressing airborne transmission.
Later, 239 aerosol scientists, indoor air quality experts as well as doctors who specialized in airborne transmission sent a letter imploring the WHO to address airborne transmission. Their plea fell on deaf ears.
Personally, I ran into this issue with a public health official in Ontario. I was advocating for fixing ventilation and use of HEPA filters at a school in August 2020. The school initially rejected my guidance based on public health advice. After discussions with the public health official who advised against spending resources on indoor air quality, he told me that only built environment people think it’s airborne and that ventilation helps. Just like cleaning companies think cleaning helps.
John Conley
An important player in rejecting airborne transmission and dismissing non-medical scientists was Dr. John Conley. His influence at the WHO and continued rejection of the evidence around airborne transmission was detailed in this article. He later complained to the CBC accusing them of character assassination.
People at the initial meeting between the WHO and Group 36 have stated that he yelled at Lidia Morawska when she was trying to warn the WHO about airborne transmission, saying “WHERE IS YOUR EVIDENCE LIDIA?”
The correct position would be to use the precautionary principle until there is incontrovertible evidence that it is not airborne.
Scaring the Public
When COVID-19 hit, it appears that public health and infectious disease doctors felt it was their job to reassure the public and reduce anxiety. Therefore, they did not want to label it airborne.
As indicated in this article about naming pathogens as being airborne:
Some of the scientists argued that it would be problematic to use ‘airborne’ for all pathogens that spread through the air. “They think it’s too scary, too frightening, has too many connotations and it will cause panic, so they chose ‘through the air’”.
Hospital Capacity and PPE Shortages
When a disease is labeled as being airborne, airborne precautions at hospitals require patients to be preferably placed in airborne infection isolation rooms. Respirators (like N95s) should also be used. At the beginning of the COVID-19 pandemic, there was a concern about capacity and hospitals, a shortage in PPE and an insufficient supply of respirators.
Concerns about PPE shortages for hospitals were also factored in when telling the public not to wear masks in early 2020. This was explicitly admitted by Dr. Anthony Fauci after he initially recommended against masking and later changed his position:
The critical issue was to save the masks for the people who really needed them because it was felt that there was a shortage of masks.
Aside from capacity considerations, hospitals in Canada restricted PPE access to nurses, as detailed here:
The basis for their restrictions was their belief that COVID-19 spread mostly through droplets and contact and not through the airborne route in healthcare settings. 30 doctors signed and attested to this erroneous belief. This was done in 2021, long after there was significant evidence that airborne transmission was significant.
The Failure Continues
This isn’t just a story about the failures in 2020 and 2021. In 2024 there is now a MERS outbreak in Saudi Arabia. WHO recently published an airborne risk calculator and documents explicitly stating respiratory pathogens, including COVID-19 and MERS spread through the air. Nevertheless, with a MERS outbreak, they recommend droplet precautions and airborne precautions for aerosol generating procedures! They haven’t learned a thing.
Lasting Legacy
Although a scientist from the WHO expressed regret over their failure with airborne transmission, not a single public health agency has apologized for getting it so wrong. It appears that instead of protecting the public, their main goal is to protect their reputation.
Respirator bans were widespread in Canada. In hospitals, vaccine clinics and other workplace settings, people were not allowed to enter wearing N95s and had to put on surgical masks which are not designed to mitigate airborne disease transmission. Teachers faced suspension because they wanted to wear proper airborne PPE. I was personally prohibited from wearing a N95 at my work. Horrible policies, all based on the advice of public health.
The biggest failure from this pandemic is not permanently addressing indoor air quality. The solutions to this would be implementing ASHRAE 241 — control of infectious aerosols, and a clean indoor air act to monitor and ensure acceptable indoor air quality. The engineering community also deserves some blame as these standards and frameworks have only been provided in 2023 when they would have been most valuable in 2020.
However, having transparency about indoor air quality through air quality monitoring was something that could have been done from the beginning. Requiring buildings to comply with an acceptable standard for indoor air quality, even if it was not as accurate as ASHRAE 241, would also have been an important step that could have been taken.
Paradigms, dogmas and rejection of evidence. Arrogance, ignorance, hubris, bad science, myths and gatekeeping. No trust in vaccines, no trust in masks and no clean air. Permanently stuck with the fastest spreading airborne disease in history. This is what the public health and IPAC world has left as a legacy from the COVID-19 pandemic.
