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Airborne Transmission of COVID-19, Highly Possible - Scientists

Medically reviewed by Ika Villanueva Caperonce, MD · Infectious Disease · Makati Medical Center

Written by Lorraine Bunag, R.N. · Updated Jun 28, 2021

Airborne Transmission of COVID-19, Highly Possible - Scientists

Even with our efforts to reduce the spread of the COVID-19 virus, it seems like the virus is always one step ahead. Now, hundreds of scientists are claiming that the virus stays in the air long enough to infect people. Is the airborne transmission route of COVID-19 possible?

Recent Development

Just recently, The Lancet compiled evidences supporting the claim that the airborne transmission route of covid-19 is possible.

Among those they highlighted was how “superspreader events” seem to occur mostly indoors. Secondly, there were instances when an uninfected person was infected by someone who they never came in contact with. Apparently, the involved were staying in the adjacent rooms of a quarantine facility. Hospital staffs contracting the infection despite wearing PPEs also seem to support the airborne transmission route of covid-19.

Perhaps, the most interesting evidence is how one laboratory study showed that the SARS-CoV2 virus can remain infectious in the air for up to 3 hours. Experts argued that large respiratory droplets don’t behave that way as they usually fall quickly to the ground.

COVID-19’s Transmission According to the WHO

According to the World Health Organization (WHO), respiratory infections, such as COVID-19, spread primarily through droplet and contact transmission. Let’s briefly define these two modes of transmission:

Droplet Transmission

To discuss droplet transmission, let’s first understand what we mean when we say “respiratory droplets.”

  • Respiratory droplets are the tiny invisible particles we produce upon exhalation.
  • These droplets are derived from our nose and mouth and could be expelled via talking, sneezing, singing, or coughing.
  • The droplets are measured in microns, which are extremely tiny.
  • Imagine, 1 micron is equivalent to 1 millionth of a meter.
  • The droplets linked to the coronavirus are about 5 microns or bigger. They are what we call “respiratory droplets.”
  • If the particle size is less than 5 microns, then it’s called “droplet nuclei”. Others would like to refer to it as “aerosols”.

It’s important to note that droplet transmission is different from the possible airborne transmission route of COVID-19.

In a nutshell, the respiratory droplets are big and heavy that they will not have the power to stay in the air long enough to infect people. In other words, the droplets will immediately fall to the ground or surfaces.

airborne transmission route of covid-19

However, if an infected person coughs, sneezes, or talks without a mask on, and someone, especially one who is not wearing a face shield or mask, is within one meter, the risk of transmission is higher.

When the COVID positive person expels the droplets, the people nearby risk getting the virus-laden droplets into their eyes, nose, or mouth.

Droplet transmission is the primary reason why the DOH is so strict about physical distancing and wearing of masks.

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Contact Transmission

Contact transmission occurs when respiratory droplets fall on to different surfaces. The virus-laden droplet can stay on the surface for hours or days. Afterward, someone can touch the surface and get the droplet to their eyes, nose, or mouth should they forget to wash their hands.

How Long Do Coronaviruses Stay on Different Surfaces?

There has been no consensus as to how long COVID-19 particles can remain on surfaces. But previous studies have noted the behavior of other coronaviruses on surfaces and found the following:

  • Copper surfaces – 4 days
  • Cardboard and paper – 24 hours
  • Wood – 4 days
  • Plastic and stainless steel – 3 days
  • Glass – 5 days

Contact transmission is the reason why we should disinfect surfaces frequently touched objects and surfaces, like door knobs, phones, light switches, and delivered groceries. Additionally, we should never touch our face unless we have thoroughly washed our hands first.

What does it Mean When We Say “Airborne?”

Now that it’s clear what droplet and contact transmissions are, it’s time to discuss the possibility of the airborne transmission route of COVID-19.

When say “airborne,” it means that:

  • The virus is present in droplet nuclei, which are smaller (less than 5 microns).
  • The virus-laden droplet nuclei stay in the air longer as they are smaller and lighter.
  • Even people who stay farther than 1 meter from a symptomatic patient can still get infected

Although more research is needed, over 200 scientists, so far, are aiming to let more people know that the COVID-19 virus “can float in the air.” And they are appealing to the CDC and WHO to back their claims.

So, Is There an Airborne Transmission Route of COVID-19?

In a recent turn of events, 239 experts across 32 countries wrote an open letter to WHO. The letter included the details of different pieces of evidence suggesting that there is an airborne transmission of the COVID-19 virus.

Before this, a group of 36 scientists led by Dr. Lidia Morawska encouraged WHO to reconsider the possibility of airborne transmission for the coronavirus. The WHO responded quickly and arranged a meeting with the group.

However, reports say that scientists who support handwashing over aerosol precautions dominated the meeting. And in the end the WHO didn’t change their stand.

Still, Dr. Morawska highlighted the following incidences, saying that airborne transmission is possible especially in “enclosed space and crowded places.”

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Events Suggesting the Possibility of Airborne Transmission

  • On March 10 in Mount Vernon, a group of choir singers met in their church for their regular Tuesday night practice. A total of 61 singers made it to the rehearsal and one of them suffered from cold-like symptoms. Later on, that person tested positive for COVID-19 and infected 52 more people, 2 of whom died.
  • In Guangzhou, China, 9 people tested positive for the coronavirus after dining near each other in an air-conditioned restaurant. The researchers believed that the air-conditioner “blew the viral droplets farther than what they might have normally gone.”
  • In Toennies meat plant in Guetersloh German, at least 1,500 staff got infected and the culprit, according to experts, could have been the circulating air inside the enclosed meat plant.

Marowska on Why It’s Hard to Face the Reality

In a paper titled, Airborne transmission of SARS-CoV-2: The world should face the reality, Dr. Morawska together with another research, Junji Cao, emphasized the importance of “facing the reality” about the possibility of COVID-19’s airborne transmission.

The researchers understand that one reason why public authorities refuse to acknowledge the possibility of airborne transmission is because they are having a hard time in “detecting” the virus in the air. After all, successfully making a study about it requires deep knowledge in the complicated principles of airflow.

The problem is the long sampling times for the studies are quite impractical. Additionally, the microbiologists who typically collect the samples are often not experts in airflow dynamics.

However, they reiterated that it’s only possible to take the necessary precautions if the national bodies responsible for the management of the pandemic acknowledge the probability of airborne transmission.

WHO on the Airborne Transmission Route of COVID-19

Despite the urging from various scientists, Dr. Benedetta Allegranzi of WHO stands by their previous claims. They stated that although they support the possibility of the airborne transmission route of COVID-19, “it is not supported by solid or even clear evidence”.

However, they also agree that airborne transmission is possible during hospital treatment or procedures that produce aerosols, like:

  • Endotracheal intubation
  • Turning a patient to prone position
  • Open suctioning
  • Bronchoscopy
  • Disconnecting the patient from a ventilator
  • Tracheostomy
  • Cardiopulmonary resuscitation

If the Airborne Transmission Route of COVID-19 is True, What Can We Do?

While there is no “incontrovertible proof” about the possibility of airborne transmission route of COVID-19, there is also no evidence to suggest that aerosols are not infective.

Because of this, scientists are pushing for the “precautionary principle.” The precautionary principle is the idea that while we still don’t have enough evidence for airborne transmission, we should still assume the worst and apply the best possible protection against the virus.

While we fully understand the importance of handwashing and face masks, we could still do things to lower our risk of contracting the virus. And that is to avoid enclosed spaces and crowded places as much as possible and improve indoor ventilation at home and work.

Key Takeaways

A growing number of scientists believe that the airborne transmission route of COVID-19 is possible, especially in enclosed and crowded places.

The WHO still urges for more evidence and investigation and still maintain that COVID-19 is mostly transmitted via contact and droplet transmission.

However, if you can avoid it, avoid crowded and enclosed spaces with poor ventilation. It’s better to be extra careful as we await more research that will help us better understand COVID-19.

Learn more about COVID-19 here. 


Hello Health Group does not provide medical advice, diagnosis or treatment.

Medically reviewed by

Ika Villanueva Caperonce, MD

Infectious Disease · Makati Medical Center

Written by Lorraine Bunag, R.N. · Updated Jun 28, 2021

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