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Jul 07, 2021

6 common myths about airborne transmission of infections

The discussions that have arisen in the waves of the pandemic question whether the virus is airborne or not, where multiple researchers and authorities often have a broad spectrum of different opinions and ideas.  Recent studies shows that the Covid-19 indeed is also airborne, thus washing hands and using face masks is to simplify the prevention measures.

No one knows exactly how this COVID-19 virus behaves, and the long-term consequences cannot be seen yet, the only thing we know for certain is that we will learn more about the virus in the future.

A group of researchers recently published an article on the topic Dismantling myths on the airborne transmission of severe acute respiratory syndrome coronavirus (SARS-CoV-2

The experts behind the study; all specialized within aerosols, ventilation, engineering, physics, virology, and clinical medicine gathered their knowledge in a review on how to prevent the spread of Covid-19 in healthcare as well as in the community. They state that it is important that we know more about airborne transmission mechanisms to find modern strategies for infection prevention.

The myths that were presented are more or less common in different situations, and the experts want to open our eyes on the fact that these statements are wrong based on current evidence. 

Let us bust the myths!

Myth 1: “Aerosols are droplets with a diameter of 5mm or less”

The diameter spectrum of aerosols spans from <1 mm >100mm. Respiratory aerosols are droplets formed from saliva and when desiccating to 20-40% of their original size they leave residues called droplet nuclei. 

Depending on the volume and direction of airflow many “large” particles can swirl around in the air much longer than the widely accepted 1-2 meters before falling to the floor. With this in mind you have to take into consideration that the aerosol and droplet distribution pattern will vary depending on the airflow. 

Myth 2: “All particles larger than 5 mm fall within 1-2 m of the source”

In a room with still air aerosols of 5-10 mm fall to the floor from 1.5 meters within 8 to 30 minutes. Most rooms have air currents of 0.1-0.2 m/s making these aerosols too small to touch the floor within 1-2 meters from the source, since a droplet in these rooms must be at least 50 mm to have a chance to land within 1-2 meters from the source. Smaller particles may even move upwards due to body heat, people movement and airflows et cetera, and can be carried over long distances and finally inhaled.

Myth 3: “If it’s short range, then it can’t be airborne”

Inhalation of contaminated aerosols can occur anywhere, but it is more likely that it will occur near the source where the concentration of aerosols is higher. If you compare it to smelling, it is likely the same phenomenon. You make notice if your friend had garlic for lunch or just smoked a cigarette when you are nearby. But if you move away, the smell fades out. If you can smell it you can inhale it, and the same goes for viruses in exhaled breath. 

Myth 4: “If the basic reproductive number, R0, isn’t as large as for measles, then it can’t be airborne”

The R-number is not related to whether a transmission is airborne or not, it only represents how many people that became infected from one infected person. And also, you can only count on the reliability of R0 if you have the possibility to identify the transmission from one person to another. 

Myth 5a and 5b: “If it’s airborne then surgical mask (or cloth face coverings) won’t work”
“The virus is only 100nm (0.1 mm) in size so filters and masks won’t work”

Studies have shown that masks are effective in both limiting exhaled particles and limiting inhalation of particles from others. 

Secondly, the virus particles often travel with a partner such as fomites, water or protein from saliva. These particles are much larger than the virus particles and are thus captured by masks or other filters. 

Myth 6: “Unless it grows in tissue culture, it’s not infectious”

Virus has been found in aerosol samples from patient rooms by different research groups. These studies very likely underestimate the amount of viable virus due to the difficulty of sampling enough virus culture to detect it at all.

Besides the usage of mask and gloves it is important to have a sufficient ventilation to minize the risk of infections. The air supply in hospitals must not only be filtrated with HEPA filters to avoid spread of particles, but also be adapted to the number of persons in the ward, movement, door openings and temperature. It is not only about a sufficient number of air changes per hour, but also the direction of the airflow should be controlled to protect both patients and staff from airborne infections.

Avidicare has many years of expertise on how to control the airflow to secure a safe environment for patients and staff. Talk to us today to learn more about how we can help you and your healthcare facility.

To get an in-depth explanation why these claims are nothing but myths, see the complete article here