How the CDC Flubbed Its Messaging on COVID Transmission

What explains the reluctance to come right out and acknowledge that we appear to be dealing with aerosol/airborne transmission of the coronavirus?

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For months now, virologists and epidemiologists have been debating a simple question about COVID-19 transmission: How small does a particle exhaled by an infected person have to be before it’s too small to spread the virus? We know that ballistic droplets, the comparatively large globules expelled when breathing, speaking or singing that fall to the ground quickly, generally don’t travel farther than six feet, and are the basis of virus-fighting guidelines like social distancing and masking. But some scientists have argued for months that there’s evidence to suggest the virus that causes COVID can also hitch a ride on droplets small and light enough to hang in the air for hours, and that these “aerosols,” as they are called, might be a substantial contributor to the spread of the pandemic.

Back in July, the World Health Organization acknowledged that aerosols might play a role in spreading COVID: “We have to be open to this evidence and understand its implications regarding the modes of transmission.” Then, this past weekend, the CDC went even further. In a change to their online primer for how the coronavirus spreads, they described COVID-19 as an “airborne disease”—in other words, a disease transmitted primarily through aerosols.

“There is growing evidence that droplets and airborne particles can remain suspended in the air and be breathed in by others, and travel distances beyond 6 feet (for example, during choir practice, in restaurants, or in fitness classes),” the updated language read. “In general, indoor environments without good ventilation increase this risk.”

Soon after the change was released, however, the CDC abruptly changed tack, claiming the update had been posted in error. “Unfortunately an early draft of a revision went up without any technical review,” Jay Butler, the CDC’s deputy director for infectious disease, told reporters Monday.

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  1. Midge

    Droplet size obviously exists on a continuum from ballistic gobs to tiny aerosols. Protocols, on the other hand, tend to be discrete. Not just discrete, but also few in number, so it's feasible for all medical personnel to recall them as needed. And the word I've heard is that medical protocol so far just hasn't had a good category for SPATs.

    Classic airborne transmission (CAT for short) is like measles: the aerosols are *very* tiny and *very* infectious. (Diseases like measles might even lower the viscosity of people's secretions to increase the fineness of aerosols produced.) There's a familiar protocol for managing CATs (unlike actual felines, who reject management). And then there's a familiar protocol for managing diseases spread by ballistic droplets. What there hasn't been, apparently, is a familiar widespread protocol for managing a SPAT (small airborne particle transmission), a form of transmission between large droplet transmission and CAT. Up till now, the protocol for "airborne transmission" has been CAT protocol, "treat it like measles" (that is, like measles in an unvaccinated population), but that would be overkill for a SPAT like Covid-19. Quoting someone who should know:

    "It’s important to distinguish SPAT from 'classic airborne transmission' (let’s call it CAT). The CAT pathogens (TB, measles, VZV) have very different transmission dynamics than SPAT pathogens, as I outlined here (R0s of >10, household transmission rates of 50-90%). The distinction is important because for most healthcare epidemiologists, using the term 'airborne' implies a common set of 'one-size fits all' interventions to prevent transmission, interventions that require resource-intensive engineering controls and PPE requirements. It is not at all clear that such interventions are required to prevent transmission of SPAT pathogens. In fact, most evidence (and real world experience) suggests that they are not. This is why the droplet-airborne dichotomy has served us fairly well over the years—either because droplet precautions appear to be pretty effective at preventing SPAT, or because SPAT is rare even among those viruses capable of it."

    https://haicontroversies.blogspot.com/2020/07/a-tiresome-spat.html

    The smallest physical units might be quantized (hence quantum physics) but macro-reality effectively happens on a continuum. Lived reality is both continuous and non-narrative. But the minds we use to perceive it latch onto narratives and categories. This is true even of minds trained for STEM fields, and what is a protocol but a story to follow for handling a particular category of scenario? A center for disease control may do plenty of research, but its first duty is to have good protocol to, well, *control* disease, including dissemination of easy-to-follow protocol for the mass public. Lacking a well-worn protocol for SPATs, the human mind has been trained to respond to "airborne" with CAT protocol, to mentally categorize all airborne transmission as CAT. And no denial of Covid-19's impact is necessary to see that mentally categorizing it as a CAT when it's not would needlessly spread fear and drain resources.

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    Adam

    Excellent COVID work as usual Andrew!

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    Logical

    For the sake of the country, please listen to me one time.

    The evidence of aerosolized transmission was no clear in Feb/March time frame, though suspected.

    That's why, Fauci, the Surgeon General, and others discouraged the use of masks for PRESERVING LIMITED SUPPLIES FOR THE HEALTH WORKERS.

    We subsequently understood that aerosolized transmission is the predominant mode.

    THEREFORE, anything on your face TRAPS the aerosols thus preventing outright or reducing substantially the chance of YOUR infection from transmitting.

    I am not not an epidemiologist but I have a Ph.D. in materials; in case you ask who the F are you. I have significant training in small particle diffusion mechanisms.

    Please wear a mask.

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    1. Mary Stine

      Thank you sir, good to hear from an expert in materials.

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    2. 2357958

      Health care workers were never going to wear cloth masks. Why did Fauci not tell the public to wear cloth masks?

      I know we've collectively memoryholed pre-2020 mask science, but Fauci was telling the truth when he said masks don't work. That was the prevailing consensus over decades about masks.

      Prove me wrong. Show studies and/or recommendations for masks from pre-2020. There's plenty of studies and recommendations. They just all happened to be anti-mask (excepting medical/N95 masks in healthcare settings). The only ones pro-mask mysteriously showed up post-covid.

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        Logical

        Who is talking about cloth masks for healthcare workers?
        Good luck with your theories.

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        1. 2357958

          You said that Fauci discouraged mask use to protect the supply for healthcare workers. If Fauci was really doing that, why didn't he recommend cloth masks to the public? My entire point is that healthcare workers were never going to wear those (and they're usually homemade anyway). How would encouraging cloth masks threaten supplies for healthcare workers?

          The explanation offered for Fauci doesn't add up.

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  4. Scott N.

    Re: masks, I think one problem is the fact that this is a fundamentally different virus situation than say, Ebola, where 1 particle has a high likelihood of killing you, so ANY breach is likely to be lethal. Richard Preston's excellent but chilling accounts tell this tale. With COVID, it's about the viral load, so it's how most people, even most vulnerable elderly will survive and may even be mostly asymptomatic, but even a young & no-conditions nurse or doctor can be struck down.

    Where the messaging has also been poor is that there's a middle ground between N95 and most cloth masks - nonwoven surgical masks (even those marked as "non-medical" or "general purpose", which tests show block a lot more viral particles.* Moreover, there are various mask braces that can be made or purchased^ that seal up the sides to make a surgical mask a near-95 or at least drastically better than a cloth or loose-fitting one. The biggest problem with disposable surgicals of course, is the waste/landfill problem; however, that's a separate issue. The other upside is that they're a lot more breathable than most cloth ones.

    Masks don't even need to be that effective to blunt a curve, since an exponential outbreak works in both directions, where small decreases in the transmission plays an outsized role both in terms of outright spread and in terms of case severity for those who do get it.

    The security theater with COVID hasn't been the masks, but instead much more the surface cleaner shortage. Relentless surface cleaning isn't as important as ventilation, and that does seem clear now.

    I also quite agree it was bad on Fauci and the SG to not wear masks early.

    * https://olv.duke.edu/news/researchers-created-a-test-to-determine-which-masks-are-the-least-effective/ - Duke study on mask types & https://medium.com/@fixthemask/why-are-melt-blown-fabric-masks-better-than-cloth-masks-cf7975bc7edf

    ^ https://www.fixthemask.com and https://www.bellus3d.com/solutions/mask-fitter are two examples

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  5. Joe1776

    I think that many experts don't know the answers and they are trying to be careful. The important thing is that people are getting logical advice as we find out more and have been for the most part since the beginning. Wear a mask inside when in public spaces and outside when you can't socially distance. Outdoors is safer then indoors. Elderly people and those with certain pre existing conditions are most at risk etc.

    The big exception was when Fauci and the Surgeon General were telling us not to wear masks early on. Fauci explained that he lied because they did not want medical staff to run short. Other than that the behaviors the experts endorsed have been fine and about as widely known as can be expected.


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    Tracie

    "We know that ballistic droplets, the comparatively large globules expelled when breathing, speaking or singing that fall to the ground quickly, generally don’t travel farther than six feet, and are the basis of virus-fighting guidelines like social distancing and masking. But some scientists have argued for months that there’s evidence to suggest the virus that causes COVID can also hitch a ride on droplets small and light enough to hang in the air for hours, and that these “aerosols,” as they are called, might be a substantial contributor to the spread of the pandemic."
    ______________________________________

    Really appreciate the distinction b/t droplets and airborne particles laid out from the first paragraph of this article. If we're going to have these words thrown around, it's really important to understand what they mean.

    However, if it gets definitively declared airborne, most people with children in school can expect to have them home the rest of the year.

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    Pat Riot

    In today's Republican installment of, "Donald Trump Does Not Exist"...

    This week, Trump's new message to Americans is, "almost nobody died from COVID in America". If nobody has died from it, then all Federal efforts to combat the virus are, of course, a waste of time. As are all efforts to mitigate the virus nationwide.

    And that's what the President is telling his followers. And that explains his administration's continued efforts to sabotage the efforts of agencies like the CDC.

    How people can defend this murdering monster is beyond me.

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  8. Pearse

    It sounds like a classic case of anointed experts not trusting the benighted plebes.

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  9. Jess

    Aerosols are simply particles smaller than 5 micrometers. Particles bigger than that are typically called droplets. We know the virus is transmitted in particles emitted by contagious people. The question is: What size particles cause the most transmission? Naturally, this is very difficult to study. You can’t randomly assign thousands of people to be sprayed with either the virus or a placebo in different sized particles.

    Besides, in reality, there is no clear dichotomy between large droplets and small aerosols. There is a continuous spectrum of particle sizes, and other important factors must be considered, such as the volume and speed of exhalation.

    Does the answer to this question of particle size really matter as far as recommended public health measures?

    We know that gathering outdoors is far safer than indoors, and that good ventilation is important if you have to be indoors. I don’t see how particle size calls that into question. As far as mask wearing, any mask than can block any sized particles is better than nothing. In fact, there is a hypothesis that even if a mask doesn’t block all particles, the wearer receives a lower dose of particles which can lead to milder disease.

    As far as distance, some infection may happen indoors at a distance further than 6 feet, but close contact still appears to be the dominant means of spread. Should we make the distance recommendation larger? That might be the most conservative measure, but schools are already struggling to maintain the six feet.

    I think the CDC statements on aerosols would have the most effect in health care settings. If aerosols are a big means of transmission than everyone needs an N95 (still in scare supply), and all Covid patients must be isolated in negative pressure rooms. As far as public health for citizens, I would prefer that the CDC stick to concrete and consistent recommendations, and stay away from the nebulous questions of particle size

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      Pat Riot

      It's not all or nothing (for the four thousandth time since this pandemic started).

      Reducing the amount of materials emitted and blocking the airflow *does* reduce the amount of material put into the air and thus the likelihood of spreading.

      And there absolutely *is* a difference between one molecule of the virus and millions, the latter making it more likely you will develop an infection and/or a more severe one. So getting a "small" drop on you is much less dangerous than getting a "large" drop on you.

      It's so absurd that we have to go over this eight months into our pandemic here in the United States, but hey, that's why we're #1.


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      Carl M

      Very thoughtful and well-informed comment.

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  10. Mike M

    I'm glad you stay on this story, because in the years to come learning from what is happening here can help us do a better job in the future. Watching this bungling in real-time has been disheartening.
    My best guess as to what happened here is 1) That there is more good evidence of some transmission from virus containing aerosol drops. 2) The report was released before they decided what do with that information, and what practical recommendations they could make to an exhausted public.
    Messaging fatigue has set in. I really think the public not really much interested in additional guidance about what to do with respect to COVID. It get the sense that we have just decided to power through with what we are doing now. In that light, how much difference do you think warning us that the already invisible droplets are even smaller would make? Hospitals might take note and step up air filtration, but they would be fools not to have already done so. I think the level of masking, distancing and limits to social gatherings have maxed out. It's vaccine or bust. Personally. I'm grateful to live in a time where vaccine is at least an option.

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