SARS-CoV-2 Is Not an ‘Airborne’ Virus

According to a CNBC article published on April 23, 2021, you are at just as much risk of being infected with SARS-CoV-2, the coronavirus that causes COVID-19, if you are 60 feet away from someone who is spreading the virus in an indoor environment as you are if you are 6 feet away. The idea that you can reduce your risk by keeping several feet of distance from others, according to the article, is false.

The ostensible reason for this is that SARS-CoV-2 is not primarily transmitted via respiratory droplets that fall to the ground relatively quickly but via the “airborne” route: smaller aerosolized droplets that can linger in the air for an extended duration and travel farther, dispersing throughout a room.

CNBC claims that it is “now known that airborne transmission plays a huge role in the spread of Covid-19”.

That claim, however, is false.

The CNBC article was reporting about a study published on April 15 in the journal PNAS (Proceedings of the National Academy of Sciences of the United States of America). Titled “A guideline to limit indoor airborne transmission of COVID-19”, the study was authored by Martin Z. Bazant and John W. M. Bush. Notably, for reasons that we’ll come to, it was edited by Renyi Zhang.

The first clue that neither of the authors are virologists, epidemiologists, or infectious disease experts is the title, wherein they mistake the name of the disease caused by SARS-CoV-2 with the name of the virus. One cannot transmit “COVID-19”. One can transmit SARS-CoV-2, which, depending on individual host factors, may or may not lead to the development of the disease called COVID-19.

Bazant is a chemical engineer, and Bush is a mathematician, both out of the Massachusetts Institute of Technology (MIT). Zhang is a chemist out of Texas A&M University. I point this out not to argue that engineers, mathematicians, and chemists have no qualifications or expertise to help further our understanding of how SARS-CoV-2 is transmitted, but simply because there is a huge disconnect between what some scientists in other fields have been saying about it and the prevailing view among infectious disease experts.

Notably, both the US Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) maintain that, while airborne transmission is possible with SARS-CoV-2 under certain circumstances, it is predominantly spread via the droplet route.

The technical description of an “airborne” virus does not include any virus that is merely capable of spreading via aerosols but refers specifically to those that are highly efficient at spreadingover a temporal or spatial distance under typical circumstances. The CDC and WHO maintain that since SARS-CoV-2 does not do so, it does not fall under the category of an “airborne” virus.

The CDC and WHO rightly observe that, contrary to the claim made by CNBC and the authors of the PNAS study, the evidence clearly indicates that close contact with someone who is spreading the virus through coughs, sneezes, or vocalization is a key determinant in the risk of becoming infected.

The CDC and WHO are certainly not infallible institutions. But on this subject, it is their position that happens to accord with the preponderance of evidence available in the scientific literature. The claim that SARS-CoV-2 should be classified as an “airborne” virus because it spreads primarily via aerosols is unsupported.

This new PNAS study provides a useful case study of how the “airborne” claim persists despite being contradicted by the evidence. It goes to show how media outlets like CNBC fail to do real journalism, how some scientists will go so far in their efforts to support their own predetermined beliefs as to make fraudulent claims, and how demonstrably false claims pass peer review in leading medical journals.

The study’s abstract contains the statement, “The importance of airborne transmission of COVID-19 is now widely recognized.” That statement by itself is true. The CDC and WHO both acknowledge the “importance” of airborne transmission, for example.

However, the introductory section takes that claim further, stating that “There is now overwhelming evidence that indoor airborne transmission associated with relatively small, micron-scale aerosol droplets plays a dominant role in the spread of COVID-19 (4, 5, 7, 17–19, 22), especially for so-called ‘superspreading events’ (25–28), which invariably occur indoors (29).” (Emphasis added.)

(Note once again that where they say “COVID-19”, they mean “SARS-CoV-2”.)

The whole study is premised upon this claim that airborne transmission not only can occur but that it is a dominant mode of transmission. The conclusion that the risk is the same whether you are 6 feet or 60 feet away is dependent on the premise that aerosol spread is the predominant mode of transmission.

However, the claim that this premise is supported by “overwhelming evidence” is demonstrably false. To show that it is false, all we need to do is to examine the sources cited by the authors to support their assumption.

The first is a commentary published in Clinical Infectious Diseases in November 2020 that appealed “to the medical community and to the relevant national and international bodies to recognize the potential for airborne spread of coronavirus disease 2019 (COVID-19).” (Emphasis added.)

(Note, once again, that it makes no sense to refer to the spread of the disease caused by the virus. It is the virus that spreads, not the disease. The terms “virus”, “infection”, and “disease” are not synonymous. Many people who become infected never develop the disease. Their immune systems efficiently eliminate the infection without them ever developing any symptoms.)

This open letter merely argued that airborne transmission was a theoretical possibility. It provided some evidence to support the conclusion that it can occur, but it does not support the claim that this is the predominant mode of transmission.

The second source cited is another commentary published in the journal Environment International on April 10, 2020. This paper argued that “there is evidence” that airborne transmission “is a significant route of infection in indoor environments.” It drew the conclusion that “it is highly likely that the SARS-CoV-2 virus also spreads by air”. Its authors expressed their opinion, “we strongly believe that the virus is likely to be spreading through the air.”

Once again, the article merely argued that airborne transmission could probably occur indoors, and it does not support the claim that this is the predominant mode of transmission.

The third source cited is a review published in Environmental Research on June 13, 2020, which cited some case studies in which it was evident that airborne transmission played “a profound role”.

However, just because this was true in some case studies does not mean that it is typical. The review does not claim that airborne transmission is the predominant mode.

On the contrary, this source contradicts the claim made in the PNAS paper, acknowledging that studies had “corroborated that COVID-19 is transmitted primarily between people through respiratory droplets and contact routes”.

(Note again that these authors, too, meant “SARS-CoV-2” and not “COVID-19”.)

The fourth source cited is a study published in Environmental International on May 11, 2020. Its authors noted with respect to airborne transmission that there was “evidence in the scientific literature of the role it can play”, but that it was “still not sufficiently investigated”. It was a modeling study that simulated viral spread and concluded that proper ventilation played a key role in reducing the potential risk of indoor airborne transmission.

The study merely observed that airborne transmission could occur in enclosed spaces with poor ventilation and, once again, does not support the claim that this is the predominant mode of transmission.

The fifth source cited is a study published in the International Journal of Environmental Research and Public Health on April 23, 2020. It noted that a few studies had been published that supported “the hypothesis of virus transmission over a distance of 2 m from an infected person”; there was “reasonable evidence about the possibility of SARS-CoV-2 airborne transmission”; it was “plausible that small particles containing the virus may diffuse in indoor environments covering distances up to 10 m from the emission sources, thus representing a kind of aerosol transmission.” (Emphasis added.)

Once again, the study merely presented evidence supporting the hypothesis that SARS-CoV-2 could be spread over a distance greater than two meters and does not support the claim that this is the predominant mode of transmission.

The sixth source cited is a study published in Environmental International on September 6, 2020, that merely observes that aerosol transmission, as opposed to droplet transmission, appears to best explain how the virus was spread in a number of case studies that had been described as a “superspreader event”.

The authors argued that it was likely not any unique characteristics of the spreader that was responsible for transmission having occurred but rather the unique nature of the event and the environment in which it took place. Specifically, these case studies provided strong evidence that airborne transmission could occur under certain conditions, such as people being gathered in an enclosed space with poor ventilation or engaged indoors in an activity like singing together.

Yet again, the study does not support the claim that aerosol spread is the predominate mode of community transmission.

The seventh study cited to support the claim is the only one that actually concludes that airborne transmission is the predominant mode, as opposed to merely acknowledging the hypothetical possibility or citing case studies providing strong evidence that it can occur in enclosed spaces with poor ventilation or where people are gathered and speaking loudly or singing together.

Published in the same journal, PNAS, on June 11, 2020, it was titled “Identifying airborne transmission as the dominant route for the spread of COVID-19”. (The authors, again, meant “SARS-CoV-2” as “COVID-19” is not the name of the virus.) The lead author of this study was none other than Renyi Zhang, the person credited as having edited the more recent PNAS paper repeating the same claim. The authors of the new study also acknowledge Zhang for having provided “important references.”

While Zhang’s prior study does claim that the airborne route is the predominant mode of transmission, it utterly fails to make that case.

I happen to have written an article thoroughly debunking that study, which I published on July 10, 2020, and which is titled “Study Fraudulently Claims SARS-CoV-2 Is Mainly Airborne”.

I encourage you to read that article to see just how illogical and deceptive the study is; but, in sum, to arrive at the desired conclusion, Zhang and his coauthors depended on a counterfactual assumption that the cumulative number of cases in a couple of selected locations, including New York City, would have continued to grow indefinitely in a linear manner had it not been for executive mask-wearing orders.

They observed that “social distancing” policies, which had been implemented prior to the mask mandate, were not associated with a flattening of cumulative case numbers. They reasoned that, since people were maintaining social distancing, the continued spread of the virus could not be explained by droplet transmission, and therefore it must be airborne.

Their conclusion that the lockdown did little to nothing to reduce the spread of the virus is logically sound, but the suggestions that the subsequent mask mandate was the cause of the reduction in case numbers, that masks are highly effective for preventing transmission via aerosols (as opposed to droplets), and that the daily case numbers would have remained steady if the mask mandate had not been issued are not.

Examining the data from New York, I showed in my article how their underlying assumption is not merely counterfactual but falsifiable. In fact, the case numbers had already been declining before the mask mandate. It’s a terrible study, riddled with factual and logical errors to such an extent that I do not hesitate to describe it as scientific fraud.

And that is the only one of the studies Bazant and Bush cite that even so much as appears to support the claim for which it is cited.

After citing those seven studies to support the claim that aerosol spread is the “dominant” mode of transmission, but which emphatically do not support that claim, they add that this is “especially” true “for so-called ‘superspreading events’, which invariably occur indoors.”

It is unnecessary to examine the sources cited to support that aspect of the claim since it is tautological that, in the relatively few case studies where transmission is believed to have occurred via aerosols rather than larger respiratory droplets, it is airborne transmission that played the dominant role.

To generalize such transmission events, documented to occur only under certain circumstances, is a fallacy of composition. Just because airborne transmission occurred in those unique events does not mean that it explains how community spread typically occurs. To generalize the findings of those case studies to any situation in which two or more people are together in an indoor environment is unscientific.

In addition to my article exposing the fraudulent nature of the prior PNAS study, I have written several other articles exposing how the media have used the claim that SARS-CoV-2 is an “airborne” virus to instill fear into people in order to manufacture consent for authoritarian “lockdown” measures. See in particular my articles “How the New York Times Lies about SARS-CoV-2 Transmission: Part 1” (July 29, 2020), “How the New York Times Lies about SARS-CoV-2 Transmission: Part 2” (August 3, 2020), “How the New York Times Lies about SARS-CoV-2 Transmission: Part 4” (August 21, 2020), and “Should You Be Afraid of Airborne Transmission of SARS-CoV-2?” (December 9, 2020).

In conclusion, CNBC’s claim that airborne transmission has been proven to play “a huge role” in the community spread of SARS-CoV-2 is demonstrably false. The referenced study does claim that studies have established airborne spread as the predominant mode of transmission, but that claim is demonstrably false.

(Evidently, despite the controversial nature of their claim, the author of the CNBC article, Rich Mendez, took the study authors at their word, without questioning their premise and without checking their sources to see whether what they were saying was true; which is to say, without doing any kind of real journalism.)

Five of the sources cited to support the premise merely acknowledged the possibility of airborne transmission without suggesting that this is the predominant mode.

One contradicted the claim by acknowledging that studies had established droplet transmission as the predominant mode.

And the only one that even appears to support the claim is similarly grounded in a demonstrably false premise.

In this matter, the CDC and WHO are correct to point out that the cumulative evidence shows that the virus is predominantly spread via respiratory droplets, whereas airborne transmission plays a more minor role; while it can occur under certain circumstances, most transmission events are readily explained by droplet transmission occurring when people are in close proximity to each other for an extended duration.

Contrary to the claim made by CNBC and the reported PNAS study, under typical circumstances, close contact is a key determinant in the risk of transmission occurring.

The key takeaways are that the media routinely prefer to do political advocacy through fearmongering rather than doing journalism, scientists frequently succumb to their own confirmation biases, sources cited frequently do not support the claims for which they are cited, and the peer-review process for medical journals frequently enables demonstrable misinformation to be propagated by the media as “science”.