The public guidance on “airborne” vs “droplet” transmission is deeply harmful. Public health officials have too-narrowly defined the word “airborne”. In choosing jargon over plain language, they’ve misled the public.
To minimize confusion some scientists are calling for the clearer terminology for describing transmission through the air. A recent letter in Science argued that we should use the terms “aerosols” vs. “droplets” with a size threshold of 100 µm which “more effectively separates their aerodynamic behavior, ability to be inhaled, and efficacy of interventions”. [1]
I understand the distinction, but the terminology should be renamed imho, to something like "epidemiologist airborne". Because to the layperson it definitely is transmitted "through the air", implying again in everyday terms "airborne transmission".
After this pandemic, doctors and scientists are going to have to come up with more media-friendly terms from now on.
The problem is that "airborne droplets" and "airborne" sound too similar and it's very hard for regular people to understand what that means. "Airborne droplets" means that viruses need saliva to transmit between people. "Airborne" means that the virus only needs dust particles to transmit to other people. Measles is airborne transmission, which means that if someone with measles enters a room, that room can be infectious for 12+ hours because viruses will be infectious in the dust. If someone with coronavirus sneezes in a room, the large heavy droplets will quickly fall to the ground. If you breathe in the droplets then you can catch the virus, but these only stay in the air for seconds. However, there are microdroplets which stay in the air for 30+ minutes depending on the air currents.
So there is a distinction between them. If coronavirus were truly airborne, then we would all need to wear masks all the time, even when no one is around. No where would be safe and we would have to implement extremely strict lockdowns.
But the fact that scientists and doctors have chosen to use the term "airborne" in both have made it extremely confusing and given how quickly information and misinformation is disseminated these days, they need to choose terms with care from now on.
> Please understand that airborne has a scientific meaning, and that is the terminology that scientists use. There is no actual clinical evidence of the airborne transmission of COVID.It is spread through large droplets.
At this point, it's expert consensus that airborne transmission of COVID is a significant if not the major route of transmission[1].
If you asked 10 average people what they think "airborne" means in this context, I doubt they'd say there is a difference between wet and dry transmission. I'd say for the purposes of argument, if a guy coughs violently on you because he's sick there is risk you could get Ebola. If a guy vomits in the subway car, apparently there is a risk of Ebola transmission. I've been on the subway cars and in taxi cabs it happens more than you think. Do you think they bleach all of those things adequately? No way, the financial incentives don't align to properly do it.
The government is using semantics and spin to their advantage by saying it isn't airborne via dried viral transmission. The WHO agrees[1] that it also isn't airborne, but also admits surfaces can transmit the virus.
Most officials omit this detailed explanation since they have no adequate explanation of how to decontaminate the urban environment en masse if an outbreak does occur.
In the end we all have to assess our own risk profiles. Will I stand or sit next to somebody coughing? I doubt it. Or will I take mass transit if I can easily walk to where I need to be by leaving a bit earlier? Nope.
Years later I still run into people not aware of the semantics and the difference between a disease being an aerosol and a disease being airborne. Which smacks of poor communication.
The title while technically correct stokes fear more than anything else. The article goes into depth on how “airborne” is not terribly different than what we know now about aerosols hanging in the air. Most people will read the title and react at too large of a scale, while the only real insight should be that in crowded indoor places with poor ventilation (offices, restaurants), you may be able to get infected even when socially distancing.
That is much more reasonable and solvable. Airborne is a overused Hollywood term that makes most people think it floats on the wind and infects you anywhere, anytime.
I appreciate the distinction you're making here. I don't have enough facts to prove or disprove it.
But, I'd like to ask: are you suggesting that aerosolized droplets cannot be seriously spreading this disease because they will evaporate almost instantly?
I ask because there is quite a bit of research suggesting that aerosolized droplets are spreading the disease, and can hang int the air for a substantial period of time. Do you think this is wrong? If it is wrong, why do you believe people are suggesting aerosolized transmission?
I don't think anybody's claiming it's the primary source of transmission, but the way you keep phrasing it, it's like we have to choose between droplets or aerosol transmission. There's at least limited evidence it can be transmitted both ways, and maybe it's better to err on the side of caution?
Well that March 2020 quote is still correct, isn't it? You as a layperson just think that airborne means something it doesn't mean for virologists (aerosol transmission <> airborne virus).
So the tweet certainly was a typical science communication error, i.e. they forgot that words can have different meanings in different milieus, but it wasn't wrong.
Aye, that brings up another issue. What exactly does “airborne” mean? The assumption early on was that Covid was not airborne, and required droplets of a certain size, though I think that changed over time.
Airborne transmission is different from droplet transmission as it refers to the presence of microbes within droplet nuclei, which are generally considered to be particles <5µm in diameter, can remain in the air for long periods of time and be transmitted to others over distances greater than 1 m.
It’s not a mere semantic debate - if I understand correctly (not a virologist or anything) the implications are huge.
Droplets are ejected from the face and basically fall straight to the ground. This is what makes things like six feet “socially distancing” rules effective - you basically need to be in a direct, face-to-face interaction with someone to spread the virus. Airborne transmission in the technical sense means that the virus can float along in the air, potentially for hours in a poorly ventilated space: most social distancing NPIs become nearly meaningless. Staying outside or improving indoor ventilation become the big things that matter.
Also, droplets are large and are stopped effectively even by the sort of cheap, relatively loose-fitting masks people are wearing. If airborne transmission is a major problem, that’s no longer really the case; we all need N95s to make much of an impact.
I also think that part of the resistance to calling Covid transmission "airborne" has to do with containing mass hysteria. Droplets are "things," matter we can wipe away, dodge like bullets in The Matrix. A virus being airborne instills an even greater level of fear then is already apparent, because "airborne" takes the control out of it. "How can we clean the air?" Air isn't a "thing." Even the arguments for the airborne theory (which I'm partial to believe) are basically trying to make manageable a concept that seems impossible to manage--the cleaning of the air, the idea that airborne does not necessarily mean "out of our control."
The traditional classification system for disease transmission is "contact", "droplet", and "air borne". This is the system that has been taught for well over half a century to every doctor and epidemiologist in the world. But the system is overly simplistic.[1] And that's because the system is based on faulty models from the 1950s that were never revisited or questioned until relatively recently.[2]
During the Ebola outbreak it was still medical heresy to question the droplet/air borne dichotomy. There were just a handful of scientists (one very loud one--Osterholm, I think) pressing the issue. Subsequent research after Ebola vindicated their arguments, but it can take a long time for good science to displace bad science, especially in the conservative medical community, and especially when the new science doesn't make for simple decision trees. The irony is that the old models made (and still make) typically conservative health professionals overly optimistic about the difficulty of transmission of various types of diseases.
[1] See, e.g., Michael T. Osterholm, et al, "Transmission of Ebola Viruses: What We Know and What We Do Not Know", February 19, 2015, https://mbio.asm.org/content/6/2/e00137-15#sec-7 (links directly to the section "The Complexities of Aerosols and Droplets: A Changing Paradigm").
[2] "Medical and infection control professionals have relied for years on a paradigm for aerosol transmission of infectious diseases based on very outmoded research and an overly simplistic interpretation of the data. In the 1940s and 50s, William F. Wells and other 'aerobiologists' employed now significantly out-of-date sampling methods (eg, settling plates) and very blunt analytic approaches (eg, cell culturing) to understand the movement of bacterial aerosols in healthcare and other settings. Their work, though groundbreaking at the time, provides a very incomplete picture." Lisa M. Brosseau, Rachael Jones, "Health workers need optimal respiratory protection for Ebola", September 17, 2014, http://www.cidrap.umn.edu/news-perspective/2014/09/commentar....
EDIT: And here's a 2019 paper about aerosol transmission of influenza, disputing the droplet orthodoxy, that suggests the continuing predominance of the old models: Timo Smieszek, Gianrocco Lazzari & Marcel Salathé, "Assessing the Dynamics and Control of Droplet- and Aerosol-Transmitted Influenza Using an Indoor Positioning System", February 18, 2019, https://www.nature.com/articles/s41598-019-38825-y ("virtually all studies assessing the dynamics and control of influenza assume that it is transmitted solely through direct contact and large droplets, requiring close physical proximity").
There's one key paragraph buried in the article that will help a lot of people:
> However, to date, there is also no evidence of truly long-range transmission of COVID-19, or any pattern of spread like that of measles. Screaming “it’s airborne!” can give the wrong impression to an already weary and panicked public, and that’s one reason that some public-health specialists have been understandably wary of the term, sometimes even if they agreed aerosol transmission was possible. Cowling told me that it’s better to call these “short-range aerosols,” as that communicates the nature of the threat more accurately: Most of these particles are concentrated around the infected person, but, under the right circumstances, they can accumulate and get around.
Translation: people can get infected further away than with larger droplets -- especially in stuffy, enclosed environments -- but distance still reduces the risks.
reply