By: Christopher Sirota, CPCU
Disease experts reportedly would like to make a clear distinction between the COVID-19 virus and diseases traditionally considered airborne diseases, such as tuberculosis and the measles: in other words, COVID-19 does not transmit in the same way.
To be clear, we previously posted that there is reportedly a risk that the novel coronavirus (SARS-CoV-2), which causes COVID-19, may be transmitted through the air from an infected person within so-called aerosols—the very tiny particles of saliva, mucus and water that everyone exhales when, for example, talking, singing, coughing and sneezing. This concern reportedly continues. For example, we previously noted two example studies: one pre-print study that was published in April 2020 that examined air and surface samples around 13 patients that were pulled from the Diamond Princess cruise ship; another, published in June 2020, included comparisons of aerosols produced when wearing different types of masks. Both studies concluded, in part, that some precaution against transmission via virus-laden aerosols is recommended regarding COVID-19 patients in healthcare settings.
That said, an article in Vox explains that not only are experts still debating about labeling the COVID-19 virus as an airborne disease, but that experts have been having a similar debate for nearly 100 years regarding whether or not influenza is truly an airborne disease; the argument is the same, underscoring that the flu does not spread through the air like tuberculosis or the measles.
Droplets and Aerosols
At the beginning of the pandemic, concerns were reportedly focused on viral transmission via large respiratory droplets directly from person to person or from contact with contaminated fomites (e.g. surfaces like doorknobs, bed linens and handrails).
Various studies then refocused concerns to smaller aerosol particles: according to a 2019 BMC Infectious Diseases research commentary, virus-related aerosols "refer to particles in suspension in a gas, such as small droplets in air" that are smaller than 5–10 μm in diameter, a size that is generally understood by experts to be able to penetrate various parts of the human respiratory system. A related April 2020 National Health Institute report regarding healthcare worker exposure to SARS-CoV-2 noted that "[s]neezing and coughing are effective aerosol generators, but all forms of expiration produce particles across a range of sizes."
Back in July 2020, according to a New York Times article, a letter signed by over 200 scientists from over 30 countries urged the World Health Organization (WHO) to alter their recommendations to address potential aerosol transmissions of the novel coronavirus.
Experts Begin to Reconsider "Airborne Transmission" Category for COVID-19
Vox explains the more recent concerns as follows:
When it comes to Covid-19, one of the first questions epidemiologists tried to answer was: Is the virus spread in the dust that floats [as an aerosol] or the big drops that fall?
If it’s the small dust [an aerosol], alarm bells go off. These are the prototypical airborne diseases. They include measles, chickenpox, and tuberculosis, and they are extremely contagious. On average, one person infected with measles will infect 12 to 18 others.
If it’s the big drops, it’s still concerning. Diseases like the flu, whooping cough, the common cold, and coronaviruses are primarily large droplet-borne. With these diseases, only the closest contacts to an infected person get infected because large droplets quickly fall to the ground (within 6 feet or so). It’s also possible for these big drops to fall on surfaces, and those surfaces can become contaminated too. Luckily, in the case of COVID-19, there’s a growing consensus that getting sick from touching contaminated surfaces is rare.
Per the article, it seems that experts still point to the ample evidence which supports the current understanding that COVID-19 spreads when a person inhales viral-laden droplets from an infected person in close proximity. Also, per the article, experts still consider indoor, poorly ventilated locations as having a greater potential of allowing contaminated aerosols to linger in the air.
That said, some experts are reportedly uncomfortable making any distinction between the size of the contaminated particles, opining that it doesn't alter the recommended precautions; however, they further note that categorizing the COVID-19 as a true airborne disease that is as contagious as the measles may trigger unnecessary protocols, and cause more confusion.
Of interest, according to the article, one expert opined that the difference in the viscosity of the mucus created by each different disease (e.g. the measles, tuberculosis, influenza, the COVID-19 virus) may be a factor that determines how potentially contagious an aerosol containing that disease may be.
Aerosol Transmission of the COVID-19 Virus Concerns Linger - July 2020
Researchers Investigate Aerosol Transmission of SARS-CoV-2 Virus - June 2020
Indoor Airflow Model May Help Mitigate SARS-CoV-2 Laden Aerosols - June 2020