The “smoking gun” of airborne COVID transmission

The article refutes a systematic review on “the role of airborne transmission of SARS-CoV-2” carried out by the epidemiologist at the University of Oxford Carl J. Heneghan and other scientists. This work, pending peer review, was funded by the World Health Organization (WHO) and published last month as preprint. It argues that “the lack of recoverable viral culture samples of SARS-CoV-2 prevents firm conclusions from being drawn about airborne transmission.”

“This conclusion, and the wide dissemination of the findings of the review, is worrying due to the implications for public health”, respond the authors of the article in “The Lancet”, who sign, in addition to José Luis Jiménez, Trish greenhalgh (physician and specialist in Evidence Based Medicine, University of Oxford), Kimberly Prather (aerosol scientist, Univ. of California), Zeynep Tufecki (sociologist and disseminator, Univ. of North Carolina), David fisman (epidemiologist, Univ. of Toronto), and Robert Schooley (infectious disease physician and editor-in-chief of the journal “Clinical Infectious Diseases”). These scientists argue that the WHO-commissioned review “is too narrow-minded and ignores the evidence of many kinds” in favor of airborne contagion.

Infections between animals connected by a duct have been demonstrated

They argue that airborne transmission of respiratory viruses is difficult to demonstrate directly, and that heterogeneous findings from studies seeking to detect viable airborne pathogens are therefore insufficient grounds to conclude that a pathogen is not transmitted by this route, if all the evidence indicates otherwise. “Decades of painstaking research, which did not include the capture of live pathogens from the air, demonstrated that diseases once thought to be spread by droplets are transmitted through the air,” they note.

The Lancet article lists 10 streams of evidence that support the hypothesis that SARS-CoV-2 transmission is primarily airborne:

Super contagion events

They are considered the “engines” of the pandemic, and include multiple infections that occurred in choir concerts, cruise ships, slaughterhouses, nursing homes and prisons, among other places. Their detailed analysis cannot explain drop or surface contagion and suggests that the airway is dominant.

Quarantine Hotels

Have been verified contagions between isolated people in adjacent hotel rooms but they had never been in direct contact.


The spread of the virus by asymptomatic or presymptomatic patients who do not sneeze or cough, it accounts for between a third and 59% of new cases, which supports that airborne transmission is dominant. It is known from direct measurements that a person emits thousands of aerosol particles and a few droplets when speaking.

Much greater contagion indoors

The contagion indoors it is substantially higher than outdoors, and ventilation reduces transmission of the virus.

Hospital contagions

Infections have been documented in health facilities where staff took precautions against contact and droplets, but whose protective equipment was designed against contagion by drops and not by aerosols.

“It is a slap in the face to the WHO, to its narrow-mindedness and resistance to accept the evidence” José Luis Jiménez – Professor of Chemistry U. Colorado


Viable virus detected in laboratory

Viable virus has been detected in the air for 3 hours, and in rooms occupied by patients who had not undergone aerosol-generating medical procedures (intubation, for example). Collecting virus samples is technically complicated, because some techniques are ineffective and the virus can be inactivated by dehydration or impact. “Measles and tuberculosis, two primarily airborne diseases, have never been cultivated from room air,” the authors argue.

Filters and air ducts

The coronavirus has been found in them, in hospitals with COVID-19 patients. The virus could only reach those places by means of aerosols.

Animal experiments

It has been proven that one animal can transmit SARS-CoV-2 to another in a separate cage and only connected by an air tube.

Absence of studies refuting the aerosol hypothesis

The authors assure that there are no studies that refute the hypothesis of airborne transmission of SARS-CoV-2. The fact that some people who share the air do not catch it may be, they argue, because certain individuals barely breathe out the virus. Only a minority spread it in large numbers.

Little evidence in favor of droplets and fomites

They argue that the fact that there are more infections in proximity is not due to droplets, but to the higher concentration of aerosols in the vicinity of the emitter. “The erroneous assumption that transmission through proximity involves large respiratory droplets or fomites [objetos] it has been used for decades to deny airborne transmission of tuberculosis and measles, ”they argue. They point out that this has been a “medical dogma”, as has the “arbitrary limit” of 5 microns between aerosols and droplets, when particles up to 100 microns in size are aerosols.

José Luis Jiménez concludes that this and other publications in the most prestigious journals “are a slap in the face to the WHO, whose narrow-mindedness and reluctance to accept the overwhelming evidence of airborne transmission – as well as to clearly state that transmission by surfaces is rare. – It is causing greater infections and making it difficult to control the pandemic ”. Jiménez urges the WHO to rectify, “given the slowness of vaccination in many countries and the appearance of new, more contagious and lethal variants, and the possibility that vaccines will work less well against some of these variants, present or future.”

The “BMJ” also affects aerosols

An editorial written by experts from the “British Medical Journal” (“BMJ”), another of the most prestigious medical journals, argues that any future attempt to reduce the spread of COVID-19 must focus on addressing the close transmission of the virus through the air. , which is considered the main route for its circulation.

Breathing experts from the “BMJ” argue that It is now clear that SARS-CoV-2 is more likely to be transmitted between people at close range through inhalation rather than contact with longer-range surfaces or air routes, although these pathways can also be causative.

The COVID-19 pandemic “has helped redefine the airborne transmission of viruses,” say experts from the universities of Leicester, Napier (Edinburgh), Hong Kong, Virginia Tech (USA), and the NHS Lanarkshire Medical Center ( Edinburgh).

After alluding to the confusion about the definitions of airborne infection transmission of the last century, the authors emphasize that “if a person can inhale particles, regardless of their size or name, they are inhaling aerosols. And although this can happen at a long distance, it is more likely to happen when you are close to someone, because the aerosols between two people are much more concentrated at a short distance, as is the case when you are near someone who is smoking.

For all of it urge to ventilate the interiors and to use masks with high quality filtering and optimal fit to the face.


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