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jljcolorado's profile
Prof. Jose-Luis Jimenez
Prof. Jose-Luis Jimenez
Prof. Jose-Luis Jimenez
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@jljcolorado

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Prof. Jose-Luis JimenezVerified account

@jljcolorado

Dist. Prof. Chem. & CIRES, Univ. Colorado. #HighlyCited2021, Fellow AAAR & AGU. Aerosols, pollution #EndFossilFuels #COVIDisAirborne http://Bit.ly/FAQ-A  http://Bit.ly/c-est 

Boulder, CO
colorado.edu/chemistry/jose…
Joined July 2009

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    1. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

      1/ Understanding CDC’s updated guidance that aerosols are the main mode of SARS-CoV-2 transmission CDC recently updated its guidance. It is worded in a confusing way & this makes it a little self-contradictory. This is causing some confusion, so I’ll try to explain it here

      18 replies 397 retweets 787 likes
      Show this thread
    2. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

      2/ Bottom line 1 : most important new text is: “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.” Particles here (and this thread) = either aerosols or droplets (NOT virions)pic.twitter.com/PCV9Fpx80L

      1 reply 44 retweets 162 likes
      Show this thread
    3. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

      3/ **Inhalation = aerosols**, period, full stop. We’ll review the history later. They also use the word "droplet," but not consistently with current or historical WHO/CDC definitions, we'll get to that soon

      1 reply 25 retweets 121 likes
      Show this thread
    4. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

      4/ Bottom line 2: Also very important text: “Airborne viruses, including COVID-19, are among the most contagious and easily spread. Some viruses are highly contagious, like measles, while other viruses do not spread as easily.pic.twitter.com/CWi05fWeA2

      3 replies 34 retweets 122 likes
      Show this thread
    5. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

      5/ The virus that causes COVID-19 appears to spread more efficiently than influenza, but not as efficiently as measles, which is highly contagious.” (yours truly has been stating the idea in last sentence for months, e.g. https://www.medscape.com/viewarticle/934837?src=uc_mscpedt&faf=1#vp_1 …)

      3 replies 27 retweets 156 likes
      Show this thread
      Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

      6/ So **Inhalation is thought to be the main way the virus spreads.** What particles can be inhaled? Inhalation is the flow of air into our respiratory system due to breathing (https://en.wikipedia.org/wiki/Inhalation )

      10:50 PM - 20 Sep 2020
      • 23 Retweets
      • 98 Likes
      • Dreamer 2.0 🌻🧚‍♀️🌻 Riikka Kevo 🌬 #COVIDisAirborne🦠 Karen Cohn #BetterMasksInSharedAir #CleanSharedAir INGENIERIAYPDI Montana Gal g 🇺🇸🇫🇷 The Dystopic Redhead Vanessa P Misaki
      2 replies 23 retweets 98 likes
        1. New conversation
        2. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          7/ EPA gives us the summary of a lot of research on deposition of inhaled particles in the respiratory tract at https://www.epa.gov/pmcourse/particle-pollution-exposure … So basically particles up to ~100 um can be inhaled. Larger particles cannot.pic.twitter.com/i25qw30oKW

          1 reply 20 retweets 83 likes
          Show this thread
        3. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          Prof. Jose-Luis Jimenez Retweeted Linsey Marr

          8/ Droplets are defined as particles that fall in 1-2 m & infect by impact on eyes, nostrils, or mouth Let’s review the history of "droplet" for disease transmission (we are very close to submitting a paper on this history, so it is fresh in my mind):https://twitter.com/linseymarr/status/1278036517890347008 …

          Prof. Jose-Luis Jimenez added,

          Linsey MarrVerified account @linseymarr
          We're rehashing the same arguments from 100 years ago. Hopefully we'll learn this time around. Collaborating with historians @EThomasEwing Katie Randall and Lydia Bourouiba @jljcolorado to look at history on airborne transmission and why we haven't made much progress in 100 yrs. https://twitter.com/EThomasEwing/status/1278028106809434116 …
          2 replies 22 retweets 90 likes
          Show this thread
        4. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          9/ “Droplets” in disease transmission arose from the work of Carl Fuggle in 1890s. Using collection on agar plates, he showed that bacteria expelled from the mouth were observed close but not far from the subjects.https://zenodo.org/record/1686460#.X2gmwmhTljE …

          1 reply 16 retweets 72 likes
          Show this thread
        5. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          10/ Charles Chapin, President of the American Public Health Association, wrote a seminar book in 1910. Correctly concluded that close proximity led to respiratory infection, and that social distance worked to reduce it. That’s where social distance comes from, and it works

          2 replies 20 retweets 87 likes
          Show this thread
        6. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          11/ But why does social distance work? Unfortunately, he incorrectly attributed this observation to “sprayborne” transmission, due to Flugge’s droplets. And the said that “airbone” transmission was nearly impossible. A fateful error. Chapin's book: https://archive.org/details/sourcesmodesofin00ch …

          1 reply 20 retweets 74 likes
          Show this thread
        7. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          12/ Chapin: “former ideas [that] diseases may be air-borne are entirely erroneous; that most diseases are [...] spray-borne only for two or three feet, a phenomenon which after all resembles contact infection more than it does aerial infection as ordinarily understood.”pic.twitter.com/6ndVxeguSZ

          1 reply 12 retweets 66 likes
          Show this thread
        8. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          13/ Let’s take that in for a moment. According to Chapin, SPRAY-borne infection, due to Flugge’s droplets, explains “contact infection," i.e. infection in close proximity (2-3 ft). AIR-borne does not.

          1 reply 12 retweets 63 likes
          Show this thread
        9. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          14/ Chapin says not enough evidence to rule out airborne infection. But still states that airborne infection is nearly impossible (“we are warranted to discard it as a working hypothesis”).

          1 reply 10 retweets 62 likes
          Show this thread
        10. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          15/ Why does he discard airborne infection? Because he new that social distance + hygiene worked and: “It is impossible, as I know from experience, to teach people to avoid contact infection while they are firmly convinced that the air is the chief vehicle of infection.’’pic.twitter.com/PrWUPPf4Bx

          1 reply 18 retweets 82 likes
          Show this thread
        11. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          16/ Chapin’s position becomes the new paradigm, and it has reigned successfully until now. Airborne transmission is resisted, as it has for COVID-19. Only very contagious diseases (+TB) are proven, as evidence becomes undeniable.

          1 reply 14 retweets 72 likes
          Show this thread
        12. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          17/ Leading to *confusion of this artifact of history (only v contagious accepted as aerosol), with a law of nature.* Stated in arguments like "if COVID-19 was aerosol, spread would be much larger, R0 would be much larger, we would see long-range transmission" etc. All false

          1 reply 17 retweets 85 likes
          Show this thread
        13. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          18/ Wells in 1934 at Harvard studies the droplet vs aerosol problem. He correctly determines that the aerosol-droplet separation is at ~100 um. https://academic.oup.com/aje/article-abstract/20/3/611/280025?redirectedFrom=fulltext …pic.twitter.com/vF5yGiJiCr

          1 reply 17 retweets 70 likes
          Show this thread
        14. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          19/ Wells clearly defines droplet and airborne infection, consistent with Flugge and Chapin (who had defined “droplet infection proper”). (Note that “proper droplets” are larger than 100 um, and thus we know now they are not inhalable).pic.twitter.com/7BYAbruZRO

          1 reply 12 retweets 61 likes
          Show this thread
        15. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          20/ Back to the present: CDC defines droplet infection as caused by projectiles E.g. see slide from the presentation by Dr. Butler (CDC's Deputy Director for Infectious Diseases) at recent workshop of the US National Academies of Sciences, Engineering, & Medicine (pres. #5):pic.twitter.com/yIZlFQVBGE

          1 reply 18 retweets 64 likes
          Show this thread
        16. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          21/ As recently as this @NASEM workshop on 26-Aug-2020, CDC was stating (via Dr. Butler) that SARS-CoV-2 was spread mainly through “droplets that can land in the mouth, noses, or eyes of people” https://www.nationalacademies.org/event/08-26-2020/airborne-transmission-of-sars-cov-2-a-virtual-workshop …pic.twitter.com/hBULb5VIjI

          3 replies 20 retweets 62 likes
          Show this thread
        17. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          22/ Consistent with historical practice at CDC. E.g. as summarized in 2007 paper from Y. Li’s group (https://onlinelibrary.wiley.com/doi/10.1111/j.1600-0668.2007.00469.x …), leader in disease transmission. “Droplets [..] are propelled a short distance through the air, and deposited on the host’s [eyes, nostrils], or mouth”pic.twitter.com/WkAE9qvRph

          2 replies 10 retweets 54 likes
          Show this thread
        18. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          23/ The same is true for the WHO, e.g. their famous video showing the ballistic “angry birds” flight of the droplets (https://twitter.com/WHO/status/1244258441880797184 …):pic.twitter.com/ftKA8RFPws

          1 reply 11 retweets 52 likes
          Show this thread
        19. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          24/ And this is clearly what the latest WHO brief says (9-Jul): “droplets can reach the mouth, nose, or eyes” while “within 1 metre”. This is consistent with all the historical definition of droplets. https://www.who.int/publications/i/item/modes-of-transmission-of-virus-causing-covid-19-implications-for-ipc-precaution-recommendations …pic.twitter.com/uveW7BVRWY

          1 reply 9 retweets 55 likes
          Show this thread
        20. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          25/ It is also discussed in the WHO brief that aerosols could be inhaled and lead to infection. Note that the word “inhale” is only present in this document for aerosols, and never for droplets.

          1 reply 9 retweets 56 likes
          Show this thread
        21. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          26/ Also note the dismissive tone about aerosols in the 9-Jul @WHO brief: “hypotheses… theories…” which continues later in the document. In my experience, nobody has read that document and concluded that aerosols were major. Possible maybe, but very uncertain.

          1 reply 9 retweets 52 likes
          Show this thread
        22. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          27/ So it is extremely clear what droplets & aerosols are for disease transmission, per history, CDC, WHO Droplets are ballistic projectiles, fall to the ground 1-2 m, infect by impact on eyes / nostrils / mouth Aerosols float in air for longer times, and infect by inhalation

          2 replies 26 retweets 87 likes
          Show this thread
        23. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          Prof. Jose-Luis Jimenez Retweeted Prof. Jose-Luis Jimenez

          28/ CRITICAL reminder : - to be droplet & fall to ground, need > 100 um. - Being a projectile also requires > 100 um (when talking, a projectile requires > 300 um). See this thread and refs therein:https://twitter.com/jljcolorado/status/1292880342227984385 …

          Prof. Jose-Luis Jimenez added,

          Prof. Jose-Luis JimenezVerified account @jljcolorado
          1/ Aerosols, droplets, & “flexible droplets” Trying to clarify key aspects. Details complex, give bottom lines 1st: Bottom line 1: If fall within 1-2 m of the person (WHO or CDC droplets), then **have to** infect by ballistic impact (“angry birds”). Cannot infect by inhalation pic.twitter.com/rixqF4iSrI
          Show this thread
          1 reply 17 retweets 59 likes
          Show this thread
        24. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          29/ And to be inhalable, need < 100 um. So there is a clear boundary between droplets and aerosols at 100 um For much of the 20th Century, droplets and aerosols were separated at 100 um for infection purposes in guidance and papers, with references tracing back to Wells (1934)

          1 reply 13 retweets 52 likes
          Show this thread
        25. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          Prof. Jose-Luis Jimenez Retweeted Linsey Marr

          30/ But at some point in the later 20th Century, an error is introduced, for reasons we will explain when our history pre-print is available (https://twitter.com/linseymarr/status/1278036517890347008 …) As a consequence of the error, health orgs start stating that the droplet-aerosol boundary is at 5 um

          Prof. Jose-Luis Jimenez added,

          Linsey MarrVerified account @linseymarr
          We're rehashing the same arguments from 100 years ago. Hopefully we'll learn this time around. Collaborating with historians @EThomasEwing Katie Randall and Lydia Bourouiba @jljcolorado to look at history on airborne transmission and why we haven't made much progress in 100 yrs. https://twitter.com/EThomasEwing/status/1278028106809434116 …
          1 reply 13 retweets 58 likes
          Show this thread
        26. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          31/ The 5 um error happened long enough ago, that for many people active today, 5 um is the only definition they may have ever known. And it is still an error.

          2 replies 14 retweets 58 likes
          Show this thread
        27. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          Prof. Jose-Luis Jimenez Retweeted Adam Hamdy

          32/ Fauci admitted recently that the 5 um aerosol/droplet boundary is an error:https://twitter.com/adamhamdy/status/1304120806943928329 …

          Prof. Jose-Luis Jimenez added,

          1:33
          Adam Hamdy @adamhamdy
          Dr Anthony Fauci explains scientists have got it wrong for many years, that aerosolised particles can linger in the air much longer than previously thought, and singing and speaking play a significant role in transmission. How long will it take the UK government to catch up? pic.twitter.com/L8b6AvwD0A
          Show this thread
          1 reply 19 retweets 64 likes
          Show this thread
        28. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          33/ The @NASEM workshop also concluded that 100 um is the correct aerosol-droplet boundary, and that 5 um is incorrectpic.twitter.com/g0CV0UxlmK

          1 reply 8 retweets 51 likes
          Show this thread
        29. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          34/ Indeed 5 um makes no sense. Particles of 5 um can float in the air for 30 min. This is from the “Aerosol’s 101” tutorial in the CDC webpage (http://www.cdc.gov/niosh/topics/aerosols/pdfs/Aerosol_101.pdf …):pic.twitter.com/IE5NTcQTm4

          2 replies 12 retweets 53 likes
          Show this thread
        30. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          35/ However, 5 um error is widely adopted and repeated in many papers and guidance from CDC and WHO for decades. For example in Klompas et al (2020) in JAMA: https://jamanetwork.com/journals/jama/fullarticle/2768396 … & in very recent paper from key members of the @WHO IPC committee:https://aricjournal.biomedcentral.com/articles/10.1186/s13756-020-00779-6 …

          1 reply 6 retweets 41 likes
          Show this thread
        31. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 20 Sep 2020

          36/ Sometimes, Wells (1934) is wrongly cited for the 5 um aerosol/droplet boundary, even though he clearly states > 100 um We have found no other paper that would support why to define 5 um as anything special in the droplet-aerosol range. (Pls send to me, if you have any)

          2 replies 8 retweets 43 likes
          Show this thread
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