How a quirk of scientific jargon is confusing and endangering us.
A single case of measles can cause 12-18 other cases, because measles is “airborne” — particles of the virus linger in spaces for hours after sick people breathe or cough them out. This characteristic is uncommon, and it makes the measles virus one of the most infectious known to humans. Because airborne diseases spread so quickly, civilians and scientists alike have been nervously wondering: Is the SARS-CoV-2 coronavirus airborne?
The answer, however, is complicated. First, not everyone agrees on what airborne means. The WHO and many infectious disease researchers use a highly specific definition for “airborne” that’s not intuitive to most people. This leads to situations such as this: The CDC has recommended Americans wear face masks in certain public settings to prevent catching or spreading the disease, even though the coronavirus might not meet the CDC’s definition of airborne.
Second, the evidence needed to declare the coronavirus officially “airborne” could take years to gather, while possibly endangering people. After a large choir in Washington rehearsed together, 45 of the 60 members got sick, even though nobody was symptomatic at the time.
On an episode of Reset, host Arielle Duhaime-Ross spoke to science writer Roxanne Khamsi about the origins of the “airborne” debate, and whether we should stop using the term altogether. Below, we’ve shared a lightly edited transcript of their conversation.
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Arielle Duhaime-Ross
What exactly does airborne mean?
Roxanne Khamsi
So there is not a great answer to that question. I think that you can take a very simplistic view, which means airborne means something is in the air. I mean, if you open the dictionary, that’s what it means. … But a lot of virologists and especially a lot of public health officials have the idea that something is airborne if it is spread by aerosol and not by droplet. Now, you’re wondering, like, what is the difference between droplets and aerosols, right?
Arielle Duhaime-Ross
Yeah, that is 100 percent what I’m thinking right now.
Roxanne Khamsi
So traditionally, public health officials, at least recently, have been defining the droplet as something that’s like a ball of mucus and virus and salts that is larger than five microns in diameter that you’re kind of coughing up or spewing out. And anything smaller than that could be an aerosol that floats around … in the air because it’s lighter. Imagine like a feather or like floating in the air.
Arielle Duhaime-Ross
Okay, so there are large droplets that can float around in the air, and there are fine aerosols that last longer in the air. That’s the distinction?
Roxanne Khamsi
Right. And if you trace back where they came up with this, it goes back to these equations from the 1930s where people were trying to figure out tuberculosis and how it spread. So we’re talking about a really antiquated point of view on these things. I asked the WHO, how do you know that this [coronavirus] isn’t airborne? How do you know it’s only in droplets? And I did not get a good answer from them.
Arielle Duhaime-Ross
So why are some scientists still saying that we don’t know if the virus that causes Covid-19 is airborne?
Roxanne Khamsi
Because we don’t. The thing is, we actually don’t have evidence to say whether it’s airborne or not. In a normal setting, I mean, in settings where people are getting intubated and that’s kind of spewing this thing into the air, even the WHO says there is a risk of it being airborne in those situations, but we’re operating in an absence of evidence.
Arielle Duhaime-Ross
What I’m getting from you is that … you can’t tell me right now whether it is or it’s not. We just don’t know.
Roxanne Khamsi
Exactly. So the people I spoke with who witnessed SARS almost 20 years ago and dealt with that public health disaster, they’re saying that we should operate on the precautionary principle, that this is more easily airborne than we’re saying it is or assuming it is because it technically does travel in the air. So it is, quote unquote, airborne.
Arielle Duhaime-Ross
So is this just a language thing? Is it just that most virologists think of something being airborne as being transmitted through fine aerosols as opposed to large droplets?
Roxanne Khamsi
Completely. We’re talking about a failure of language, in my opinion. So we’re talking about a word that is failing us because it can’t really capture all the nuances of the different situations. If you’re standing in front of an ocean and you feel the splash of the huge droplets of Seaspray, those are pretty big droplets, but it’s the wind that’s carrying it to your face. So could we not consider those airborne? I think that’s what a lot of the people that study this type of transmission are saying.
Arielle Duhaime-Ross
Why do you think understanding this whole airborne situation when it comes to Covid-19 — and the virus that causes it — why do you think that’s important?
Roxanne Khamsi
I think it’s important to understand how easily transmissible this virus is in the air, first and foremost for public health workers. If we say, as the CDC said, it’s okay to wear bandanas in some … situations if you’re encountering patients or whatnot, I think that’s a problem.
[Note: The CDC has advised health care professionals on contingency plans for personal protective equipment, saying that workers may use homemade masks such as a bandana or scarf “for care of patients with COVID-19 as a last resort.” The CDC adds that homemade masks are not considered protective equipment.]
Author: Daniel Markus
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