Even more unsettled (and unsettling) science…

The CDC does another u-turn, turning a near-full 360 on how COVID is transmitted.

Spoiler Alert: It has to do with masks.
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So, how is COVID transmitted?

Initially, the science community (think: Fauci channeling China’s disinformation) told us not to worry … that COVID was not transmitted human-to-human.

Then, we were told that it was transmitted human to human (to human) … via large droplets that contaminate surfaces (think: countertops and doorknobs) and hands … and transfer by handshaking and face-touching.

We bought into that … we started washing our hands and cleared store shelves of hand sanitizers and surface disinfectants (which are still in short supply).

Then, we were told that COVID is transmitted via large droplets that are delivered when infected people cough, sneeze and spray-talk on us.

That conclusion ushered in social distancing and masks went from “won’t help, might hurt” to “best line of defense”.

That’s where we were, but a short-lived CDC guidance revision threatened to upset a big apple cart.

Here’s the back story…

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In mid-July, there was a scientific paper published that concluded:

There is significant potential for inhalation exposure to viruses in microscopic respiratory droplets (microdroplets) at short to medium distances (up to several meters, or room scale). Source

Over 200 scientists signed a letter supporting that conclusion.

But, the WHO gave it a lukewarm reception. saying:

Airborne transmission of the virus may play a role in infection, especially in poorly ventilated rooms and buildings, but we do not yet declare aerosols as a definitive contributor. Source

In other words: “We’ll think about, but, for now, keep handwashing, disinfecting and wearing masks”.

Fast-forward to a couple of weeks ago…

The CDC posted a revision to their guidance, saying that COVID is spread:

…through respiratory droplets or small particles, such as those in aerosols, produced when an infected person coughs, sneezes, sings, talks, or breathes.

These particles can be inhaled into the nose, mouth, airways, and lungs and cause infection.

This is thought to be the main way the virus spreads.  Source

In other words, the CDC was signing on to the scientists endorsed conclusion in the July research paper.

But, the CDC quickly  retracted its revised guidance.

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Now, fast forward to earlier this week.

The CDC reposted its revised guidance with a significant change.

Instead of saying:

Aerosol microdroplets are thought to be the main way the virus spreads. 

The revised-revised guidance reads:

It is much more common for the virus that causes COVID-19 to spread through close contact with a person who has COVID-19 than through airborne (aerosol)  transmission. Source

Why the change?

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My hypothesis…

In prior posts regarding mask efficacy, I’ve said:

My best science source does work with both the NIH and the Chinese science community.

Their assessment: masks are about 15% effective inhibiting the exhaling or inhaling of the coronavirus.

Why so low?

If COVID is transmitted via large droplets, masks should stop their flow, right?

That’s the rationale for wearing masks.

But, if COVID is transmitted through the air via microscopic respiratory microdroplets (i.e. aerosols) … then ordinary masks are less effective than thought.

One analogy I’ve heard:

“It’s like using a chain link fence to keep out mosquitoes”.

Think about that for a second…

That means that the CDC’s original innocuous sounding guidance had the potential to re-open the mask debate.

Of course it had to be retracted, revised and re-posted, right?

One Response to “Even more unsettled (and unsettling) science…”

  1. Neel Master Says:

    There is a group of scientists who got together because they believed WHO and CDC were moving too slowly in acknowledging the likelihood of aerosol transmission.

    However, they DON’T conclude, as you suggest above, that mask-wearing is no longer important if aerosol transmission is the dominant vector.

    See the Google doc linked in this blog post, section 7 specifically covers mask-wearing and its effect on aerosol transmission.

    https://kottke.org/20/10/how-to-protect-yourself-from-the-aerosol-spread-of-covid-19

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