Droplet or airborne? WHO says it’s ‘through the air’ 

Editor’s note: The following is a narrative adaptation of a thread on X in response to the World Health Organization’s (WHO) report on the language regarding airborne transmission.

The WHO report released Thursday is an attempt to standardize terminology used to describe the transmission of pathogens through the air. “Airborne,” “airborne transmission” and “aerosol transmission” were all used during the COVID-19 pandemic, contributing to confusion about how pathogens are transmitted.

The language wordsmithing in the report can be summarized as: “through the air” is the old “droplet” and “airborne” transmission modalities combined. “Inhalation” is the new “airborne.” “Direct deposition” is the new “droplet.”

The report gathered viewpoints from experts spanning a range of disciplines. Here are my thoughts on the great to the good to the bad to the horrible in the report.

The great: Finally, an acknowledgment that short-range airborne transmission is an integral component of all (not just COVID) airborne transmission. This is huge. It means that workers, especially health-care workers, need respirator masks (FFP2/3, N95) when interacting with patients with concerns for respiratory infections.

More great: Recognizing that aerosol behaviour exists for particles 100 microns and smaller, not the incorrect 5-micron cutoff previously used.

The good: An explicit acknowledgment that COVID is airborne. We’ve known this from the beginning, but only in the last month has the WHO really stopped hedging the language on this. No apology for the impact of the error though. That would have been nice, if wholly unexpected.

The bad: Ventilation is the only modality mentioned for airborne mitigation. No mention of filtration or sterilizations (UV/far-UV). It is strange to leave such a huge gap.

“Inhalation” is the new “airborne.” “Direct deposition” is the new “droplet.”

More bad: More multi-disciplinary engagement is needed. While it’s excellent to have airborne scientists and engineers included with the traditional WHO medical doctors, there are some key disciplines still missing: no occupational hygienists (the true mask experts), no economists or ethicists. We need all brains engaged on wicked problems.

Even more bad: The suggestion that “through the air” or “inhalation” are clarifying language over the word “airborne” is disingenuous at best. We have had good functional language here, this will obfuscate things for no discernible purpose.

Horrible: No consensus on the use of the precautionary principle, the social responsibility to protect the public from exposure to harm. This was a key problem for the SARS1 outbreak in 2003 and remained very much so in the current pandemic. To still push back on a basic public health principle is unfathomable.

Ongoing horrible: The use of “equity” to try to explain why respirator masks aren’t necessary. This would be akin to saying because there are inadequate worker protections in a foreign country, all workers around the world should have inadequate protections. Equity means everyone gets excellent protections. not reducing protections to the lowest possible common denominator. “Everyone should have an equally bad risk of getting this disabling/deadly disease” should not be a thing.

In summary, the WHO is moving forward on airborne transmission (slowly). But language changes seem forced, unnecessary and only seem to benefit those who were unable to use the word “airborne” (and recommend precautions) early in the pandemic.

I hope that the words “proposed” and “first step in a multi-step process” means that there are ways of improving things, that we are not on an inevitable path. I beseech the WHO to put public and health-care worker safety at the forefront of all discussions going forward.

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Joe Vipond


Dr. Joe Vipond is an emergency doctor in Calgary, a clinical assistant professor at the University of Calgary, and the co-founder of the Canadian Covid Society and Masks4Canada.

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