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uchida_kawasaki
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Hiroshi Tsuji, MD, PhD, MPH🌏産業医
@Hiroshi_Tsuji
これを読めば飛沫とエアロゾルが語れそうなレビュー出ました。1) 呼吸器感染症の伝播経路は主に飛沫とエアロゾル 2)この二分法は粒子サイズのみに依存 3)カットオフは5μm 4)飛沫は1-2m飛散、それ以上はエアロゾル。この様な考え方は受け入れられ易いが、実は最新の物理学では支持されていない。1/5 twitter.com/linseymarr/sta… pic.twitter.com/pCnwHbn38v
2021-05-01 00:01:48
Linsey Marr
@linseymarr
1) Where did the 5-μm cutoff for aerosols in disease transmission come from? (It should really be ~100 μm) 2) Where did the 6' rule come from? @katierandall @EThomasEwing @jljcolorado Bourouiba & I traced the history in this preprint papers.ssrn.com/sol3/papers.cf… /1 pic.twitter.com/NJsZUUOKYf
2021-04-29 23:50:43
拡大
Hiroshi Tsuji, MD, PhD, MPH🌏産業医
@Hiroshi_Tsuji
この理解不足はWHOが当初コロナは空気感染しないと発信し撤回する等、気中対策が混乱した原因にもなったと。流体力学の専門家チームがこれら数字が出てきた歴史を紐解きながら突き止め、根拠が薄い事を紹介、最新の物理学に合わせて感染対策ガイドラインをupdateすべきと。2/5 papers.ssrn.com/sol3/papers.cf…
2021-05-01 00:01:48
Hiroshi Tsuji, MD, PhD, MPH🌏産業医
@Hiroshi_Tsuji
病院の感染制御に関わる医師から産業医、衛生工学の専門家まで広く知っておいた方が良い内容。私が個人的に勉強になったのは、エアロゾルを5μmで分けるのは間違いとは知ってましたが、そもそも5μmという数字自体が、気中の感染対策の面では根拠がない事。1-5μmが肺胞まで到達し易いのは 3/5
2021-05-01 00:01:49
Hiroshi Tsuji, MD, PhD, MPH🌏産業医
@Hiroshi_Tsuji
よく知られていますが、実は歴史的には肺の奥まで到達する事が当時感染性に寄与すると根拠無く考えられるようになり5μmが基準として使われる様になったのではと。むしろ100μmまでは床に落ちる前に蒸発し気中に漂う可能性あり。しかしそれら数値も、1-2mの距離も、気温,湿度,気流等条件で変わる。4/5
2021-05-01 00:01:49
Hiroshi Tsuji, MD, PhD, MPH🌏産業医
@Hiroshi_Tsuji
著者の1人バージニア工科大Linsey Marr氏は、近くは飛沫+エアロゾル、遠くはエアロゾル。境界はなだらかで、条件により変化するものと理解して対策すべきと最近主張してます。二分法ではない事の理解が、適切な対策に結びつくと思います。奥深い。5/5
2021-05-01 00:01:49
Hiroshi Tsuji, MD, PhD, MPH🌏産業医
@Hiroshi_Tsuji
日本でしか通用しないであろう造語の”マイクロ飛沫”は使用しない方が良い。私も昨年初めて名称聞き、今でもエアロゾルとの違い不明。明確な定義あれば教えて下さい。そもそもマイクロ(=小さい)より、エアロ(=気中)強調した方が気中対策に意識向く。飛沫と付く割にdroplet(英語で飛沫=大きめ)とも矛盾。 twitter.com/hiroshi_tsuji/…
2021-05-01 01:26:32
Linsey Marr https://www.threads.net/@linseycmarr
@linseymarr
1) Where did the 5-μm cutoff for aerosols in disease transmission come from? (It should really be ~100 μm) 2) Where did the 6' rule come from? @katierandall @EThomasEwing @jljcolorado Bourouiba & I traced the history in this preprint papers.ssrn.com/sol3/papers.cf… /1 pic.twitter.com/NJsZUUOKYf
2021-04-29 23:50:43
拡大
Linsey Marr https://www.threads.net/@linseycmarr
@linseymarr
"tracing the origins of the 5 μm threshold...ultimately revealed a conflation between various understandings and definitions of 'aerosols.' Most contemporary sources use this threshold only to explain which particles stay suspended in the air for longer times,..." /2
2021-04-29 23:53:03
Linsey Marr https://www.threads.net/@linseycmarr
@linseymarr
"yet the 5 μm distinction is clearly not based on what stays airborne but on what reaches deepest in the lungs...." /3
2021-04-29 23:53:37
Linsey Marr https://www.threads.net/@linseycmarr
@linseymarr
"It is this conflation of particle transport through the air and particle deposition in the lungs that appears to be the source of the error in distinguishing between droplet and aerosol transmission routes as defined by a 5 μm threshold." /4
2021-04-29 23:54:26
Linsey Marr https://www.threads.net/@linseycmarr
@linseymarr
Problems: this fosters misunderstanding about infectious particles not remaining airborne and codifies a particle size based on tuberculosis that does not apply to other diseases /5
2021-04-29 23:56:09
Linsey Marr https://www.threads.net/@linseycmarr
@linseymarr
CDC has historically recommended 3', even for SARS-CoV-1. Based mainly on studies showing bacteria grew on petri dishes up to a certain distance away from a person talking and limitations in visualizing small particles. /6
2021-04-30 00:00:13
Prof. Jose-Luis Jimenez
@jljcolorado
Our preprint on history of error of the 5 micron cutoff between droplets and aerosols (the real cutoff is 100 microns) & on origins of 1-2 meter rule TLDR: 5 um error was due to confusing the particles that reach the deep lung to transmit TB w/ those that fall to ground in 1-2 m twitter.com/linseymarr/sta…
2021-04-29 23:59:00
Katie Randall
@katierandall
So excited that the preprint for this is out!! It's been so neat working with @linseymarr, @jljcolorado, @EThomasEwing and Lydia Bourouiba exploring the history of how we understand the term "airborne" and what it means for public health. twitter.com/linseymarr/sta…
2021-04-30 00:09:25