Key scientific reasons why SARS-CoV-2, which causes COVID-19, is largely transmitted through the air have been listed in a study entitled "Ten scientific reasons in support of airborne transmission of SARS-CoV-2," and published in The Lancet.

Its findings add to the evidence of airborne transmission, which experts noted as "overwhelming" and should compel health officials to provide more stringent and effective measures to further protect the public.

Heated debates on how people catch the virus have been lingering for the past year. When COVID-19 spread throughout the globe in 2020, the general belief among health authorities was that SARS-CoV-2 was mainly transmitted by droplet transmission.

Aerosol vs Droplet COVID-19 Transmission

This perspective was based on a traditional binary between aerosol and droplet viral transmission, Aerosol particles are less than five micrometers and can stay suspended in the air for lengthy periods, and can travel long distances from their source.

On the other hand, respiratory droplets are much larger particles that are brought out from a source through sneezing and coughing. These particles land on the ground in seconds and would not travel.

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During the onslaught of COVID-19, the general presumption was that SARS-CoV-2 had spread through respiratory droplets, and this led public health officials to push such measures as social distancing, repeated cleaning of surfaces, and handwashing, as per the advice of the World Health Organization (WHO).

However, further studies revealed that numerous people had contracted the virus in superspreading events even if they were practicing social distancing.

SARS-CoV-2
(Photo: Wikimedia Commons)

The University of Oxford study published in The Lancet claims that there is strong and consistent proof that SARS-CoV-2 is largely spread airborne. It also argues that a respiratory droplet spread of SARS-CoV-2 is referenced from outdated and flawed transmission models.

Droplet Transmission Debunked in Several Cases

This research is based on evidence from the past year that includes case studies that documented a wide range of virus spread between people in adjacent hotel rooms and superspreading events in indoor locations that cannot be attributed to droplet transmission. The researchers claim that particles as big as 100 micrometers remain suspended in the air for longer durations of time and the traditional, fixed definition of five-micrometer aerosol particles led to a misleading notion of the SARS-CoV-2 spread.

Researchers wrote in the study that the "flawed assumption" that the virus transmission through close proximity would imply that respiratory droplets or fomites had been used to deny that an aerosol spread caused measles and tuberculosis.

They state that such became medical dogma, disregarding aerosol and droplet measurements that show mistakes in the overwhelming number of aerosols produced in respiratory activities, and the boundary particle size between aerosols and droplets.

Widespread Acceptance of Airborne COVID-19 Spread Pushed

These scientists are not alone in their push for widespread acceptance of airborne SARS-CoV-2 transmission. In February, the prestigious science journal Nature slammed public health agencies and the World Health Organization for failing to disseminate relevant information on the airborne spread.

The Nature editorial acknowledged a rising acceptance of airborne-spread COVID-19 while emphasizing that the continued social distancing, surface disinfection, and other droplet transmission measures have been confusing the public. This has led to immense investments in disinfection efforts and not in efforts that would have enhanced ventilation in indoor areas.

The Nature editors note that the lack of clarity in the risks of fomites has "serious implications." They said that costly disinfection efforts continue to be prioritized instead of allotting more resources, underscoring the importance of mask-wearing and laying down measures to enhance indoor ventilation.

The US Centers for Disease Control and Prevention still suggests that COVID-19 is mainly transmitted through droplets.  Although, a recent CDC Science Brief noted, "COVID-19  can sometimes be spread by airborne transmission."

Researchers note that the hypothesis for droplet transmission is still effective and that social distancing and mask-wearing are important tools to avoid infection. But they claim public health executives are diverting resources from implementing effective measures.

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