Thread by @jljcolorado

1/ @WHO has published a report on updated terminology for disease transmission

I've seen some debate about it. My take:

- Terminology itself is ok. Big progress
- But no recommendations of how to protect!

Report:

Press release: who.int/publications/m…
who.int/news/item/18-0…

2/ The report was likely the result of intense pressure on @WHO during the pandemic:

- They denied that #COVIDIsAirborne on March 2020
- They finally accepted it 2 years later

nature.com/articles/d4158…

@WHO 3/ To their credit, @WHO did invite some of their critics to be part of the committee.

What was the terminology before. In medical circles:

- droplet transmission: if it happened in close proximity, or if particles were > 5 microns

- airborne transmission: if it happened far

@WHO 4/ This old medical terminology was physically incorrect and made no sense whatsoever.

This is when I got involved on Twitter, trying to explain why it was just complete rubbish

E.g. my "angry birds"thread in Aug. 202:

https://twitter.com/jljcolorado/status/1292880342227984385

@WHO 5/ The old terminology had arisen in a period (~1920-2020) of extreme skepticism about the importance of airborne transmission.

We explained that in our peer-reviewed paper in the history, summarized in my pinned Twitter thread:

https://twitter.com/jljcolorado/status/1562112453948755974

@WHO 6/ @katierandall, @linseymarr, yours truly et al. investigated the origins of the "droplets vs aerosols" medical terminology in more detail

There is a peer-reviewed paper, but for most people the GREAT journalistic article by @MeganMolteni may be best:

wired.com/story/the-teen…

@WHO @katierandall @linseymarr @MeganMolteni 7/ In this context, what does the new @WHO report say?

- Acknowledges that infectious respiratory particles (IRPs) can be exhaled while breathing, talking etc. NOT just coughing and sneezing. GOOD!

@WHO @katierandall @linseymarr @MeganMolteni 8/ Describes transmission by the PHYSICAL mechanism by which the particles reach the susceptible person. GOOD!

[This was first proposed in a paper by Prof. Yuguo Li during the pandemic]

- Direct deposition of particles by ballistic trajectory (part of the old "droplets"). GOOD

@WHO @katierandall @linseymarr @MeganMolteni 9/ Airborne transmission / inhalation: when we breathe infections particles in, of any size and at any distance. Including in close proximity. GOOD

- In particular this removes the old (from 1910, see history thread) repeated error that transmission in close proximity = droplets

@WHO @katierandall @linseymarr @MeganMolteni 10/ Both the direct deposition (old "ballistic droplets") and the airborne transmission / inhalation are grouped as "through the air transmission"

This is awkward but not that important, in principle.

11? @carlzimmer has written a short article in @nytimes explaining all this, with some more links of interest:

nytimes.com/2024/04/18/hea…

@carlzimmer @nytimes 12/ A pearl on that article: a medical expert complaining that the old terminology was nice because it was simple to apply EVEN IF IT WAS WRONG

[Even it people in hospitals got sick and died because of the wrong protections -- OMG!]

Not that uncommon...

nytimes.com/2024/04/18/hea…

@carlzimmer @nytimes 13/ So overall, while not perfect, and with that awkwardness that can often arise of a "written by a large committee with strong internal disagreements", I view this as progress

@WHO still has not apologized for their huge errors. I hope they do one day. But this is progress

@carlzimmer @nytimes @WHO 14/ Now, the more important decision is WHAT DO WE DO WITH THIS?

WHEN should we use protections for airborne inhalation, such as N95/FFP2 respirators, enhanced ventilation / filtration, CO2 meters etc?

The @WHO report explicitly says that they do NOT take a position on that

@carlzimmer @nytimes @WHO 15/ Conceptually, we need a needle at a point between 2 extremes:

- A (theoretical) mild disease w/ minor airborne component. Airborne protections may not be worth the costs

- (theoretical) extremely deadly disease w/ major airborne component: definitely airborne protections

@carlzimmer @nytimes @WHO 16/ The key question, that this report doesn't take a position on, is:

When is a disease serious enough to recommend airborne protections?

@WHO doesn't want to recommend N95s if poor countries don't have them. Fears health care workers there would refuse to work w/o them

@carlzimmer @nytimes @WHO 17/ But as we have been seeing with the @CDCgov and its #HICPAC committee in the US, which is precisely trying to decide that question...

... this is NOT all about poor countries

https://twitter.com/jljcolorado/status/1750571416414535838

@carlzimmer @nytimes @WHO @CDCgov 18/ During pandemic, many experts told me @CDCgov has long been dominated by hospital industry

Which views infection protection as:

- Cost or savings for hospitals
- Health burden or benefit for health care workers

They choose savings for hospitals, burden for workers

@carlzimmer @nytimes @WHO @CDCgov 19/ Thankfully there has been enough pressure from nurses unions @NationalNurses and their allies that @CDCgov has not yet moved forward with that

It is very important. Curiously very little press coverage, @DrJudyStone of @Forbes being an exception:

https://twitter.com/DrJudyStone/status/1695147547340275924

20/ Responses to some comments below this point:

For COVID-19 is dominantly airborne

Direct deposition not demonstrated for any disease. I think unimportant, only if someone coughs in your face

Surface was long exaggerated, due to not understanding air

https://twitter.com/PrasadKasibhat1/status/1781069187076776010

21/ A new well-researched article on the @WHO new definitions of transmission, including airborne / inhalation, and direct deposition (old "droplets")

By @MeganMolteni, with input from @linseymarr @Don_Milton @JeremyFarrar and yours truly

statnews.com/2024/04/18/cov…

22/ This was NOT news for aerosol scientists and aerobiologists.

But it is a YUGE paradigm shift for infection control. At the start of the pandemic, ease of transmission in close proximity was interpreted by @WHO as droplet transmission, fall to ground

https://twitter.com/microlabdoc/status/1781354978071720277

@WHO 23/ When we met with the @WHO IPC committee headed by John Conly on 3-April-2020, Conly yelled at Lidia Morawska because THEY KNEW it was droplet, and "WHERE IS YOUR EVIDENCE LIDIA?"

So that side of the medical experts accepting physical reality is a big deal. Sad, but still big

@WHO 24/ This is the more important thing though:

- It became clear during the pandemic that the resistance to airborne was NOT only about the science.

- IPC did NOT want airborne precautions more generally used

- Governments were happy to hide behind IPC

https://twitter.com/microlabdoc/status/1781218943576785240

@WHO 25/ IPC (medical infection prevention and control) still DOES NOT want airborne protections used more widely. And they want the POWER over WHEN they should be used (as @microlabdoc points out)

That is still the major problem

https://twitter.com/microlabdoc/status/1781218943576785240

@WHO @microlabdoc 26/ But at least we've removed one important roadblock:

- many in the medical field were genuinely confused about this. Had been taught wrong stuff for decades

- @WHO, @CDCgov and others used that confusion to limit the debate and stall the measures

https://twitter.com/microlabdoc/status/1781218943576785240

@WHO @microlabdoc @CDCgov 27/ As exemplified by the battle of @nationalnurses Union with support of many experts, to get @CDCgov to ACTUALLY protect health care workers from airborne disease...

we are in a new situation, where it is harder for them to hide behind confusing errors

https://twitter.com/jljcolorado/status/1781069527117132100

28/ I see many posts lamenting that they didn't adopt the droplets vs aerosols terms

Personally I liked those. But while aerosols was clear, droplets was misunderstood by IPC. In their mind aerosols in close proximity = droplets that fall to ground

https://twitter.com/PrasadKasibhat1/status/1781157959281856982

29/ We had this debate internally w/ the group of 36 scientists

I pushed to keep droplets & aerosols. Limit droplets to ballistic droplets ONLY

Others: "we will never remove the confusion from droplets. Best to get rid of it, use new term"

Latter won

https://twitter.com/PrasadKasibhat1/status/1781157959281856982

30/ To be clear, I am NOT happy about @WHO

MAIN ISSUE is which airborne protections we use when. @WHO and @CDCgov continue to stall, keep power, decide on unclear grounds

But the narrow issue of terminology WAS A REAL PROBLEM. At least that's improved

https://twitter.com/microlabdoc/status/1781359046525677704

31/ Totally agree w/ this: @WHO, @CDCgov, and almost all health ministries need to APOLOGIZE for their HUGE BLUNDER of denying #COVIDisAirborne

They have lost the trust of many of us. Accepting their errors and apologizing would be 1st step to regain it

https://twitter.com/microlabdoc/status/1781357622857245038

@WHO @CDCgov 32/ I hope I am wrong, but I suspect medical IPC (infection prevention and control) is NOT going to be in a hurry to educate health care workers (HCWs) about these changes

If HCWs understood, they may get uppity and ask for airborne protections!

https://twitter.com/Nucleocapsoid/status/1781360611353317649

@PrasadKasibhat1 And 0.2 is very close. Per our paper (SI of ): ": 0.56 ± 0.13 m, 0.81 ± 0.12 m, and 1.06 ± 0.14 m for intimate, personal and social distances, respectively"

Not sure if people talking a lot in a very crowded subway, 0.2 m from each other?onlinelibrary.wiley.com/doi/10.1111/in…

33/ There is also some ridiculing of new term "puff cloud" by @WHO. I agree w/ Prasad that technically it is OK, was used by Lydia B. of MIT

[Also understandable it sounds silly to non-scientists that are tired of @WHO's inaction on protections!]

https://twitter.com/PrasadKasibhat1/status/1781367286978507060