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Jose-Luis Jimenez Profile picture
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8 May, 8 tweets, 4 min read
1/ A radical shift today by @CDCgov, finally aligning itself with science on the modes of transmission, and throwing away the 1910 error of considering "close contact" a mode of transmission!

cnn.com/2021/05/07/hea…
2/ Dr. Brook's, @CDCgov Chief Medical Officer:

"Modes of SARS-CoV-2 transmission are now categorized as inhalation of virus, deposition of virus on exposed mucous membranes, and touching mucous membranes with soiled hands contaminated with virus," the new guidance reads."
3/ This finally follows science, most elegantly summarized by Prof. Yuguo Li of the Univ. of Hong Kong on this recent paper:

onlinelibrary.wiley.com/doi/full/10.11…
4/ It is hard to overstate how important that is. The tradition (& error) of considering "close contact" a mode of transmission and synonym of droplets has been a huge problem for accepting the overwhelming evidence of airborne transmission.

thelancet.com/journals/lance…
5/ The mitigations need to follow the real physical modes of transmission. If inhalation at close proximity is a major part of transmission, we need better quality and better fit masks, than if we are just trying to stop droplets.

One of the key errors of the pandemic.
6/ @CDCgov also made some errors in the new web pages, as discussed in the article by @Don_Milton and at this link. But hopefully they will fix them in the near future.

sites.google.com/umd.edu/stopco…
7/ This change literally ends a **111 yr old error** conflating ease of transmission of close proximity with droplet and not airborne. Going back to Charles Chapin in 1910:

books.google.com/books/about/Th…
8/ Coincidentally, @zeynep published today a long essay in @nytimes explaining the science and the history, which I highly recommend. One of the most important articles of the whole pandemic:

nytimes.com/2021/05/07/opi…

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More from @jljcolorado

Jose-Luis Jimenez Profile picture
8 May
1/ TIME FOR SOME AIRBORNE + DROPLET HISTORY

Now that @WHO and @CDCgov have finally accepted *after a year of denial and delays* that airborne transmission is a major mode for COVID-19, it is time to review the history to try to understand why this response was so poor.
2/ Remember, the evidence is overwhelming that airborne transmission (1 to 1 in close proximity, and 1 to many in shared room air = superspreading) is the dominant mode of transmission.

3/ And probably we are being charitable by saying only "dominant." Can't find any real evidence that airborne is not 99%. Airborne can explain all the epidemiological patterns, while large droplets and fomites can't, and they are pathetically lacking ev.

Read 102 tweets
Jose-Luis Jimenez Profile picture
7 May
Empezando charla + preguntas en 2 horas (5 pm España; 12 Argentina; 11 Chile; 10 Mexico DF - otros: time.is)

"Métodos prácticos para estimar y monitorear el riesgo de contagio de COVID-19 cuando se comparte aire en interiores"

Registro: bit.ly/aireamoswebinar
El video de la charla de hoy (30 min + 1 hr de preguntas) sobre "Métodos prácticos para estimar y monitorear el riesgo de contagio de COVID-19 cuando se comparte aire en interiores" se puede ver en YouTube:

- Diapositivas webinar de hoy "Métodos prácticos para estimar y monitorear el riesgo de contagio de COVID-19 cuando se comparte aire en interiores": drive.google.com/file/d/1BNX28I…
- Diapositivas mas generales: Bit.ly/COVID-aerosols2
- Estimador de contagio: tinyurl.com/covid-estimator
Read 4 tweets
Jose-Luis Jimenez Profile picture
6 May
1/ Un resultado importante así que lo pongo también en español:

Las barreras de plexiglás no sólo no disminuyen el riesgo de contagio en las escuelas. AUMENTAN el riesgo, según un articulo en Science.

Esto sólo se explica si el contagio por el aire es dominante.
2/ Y todo el artículo es muy interesante: las escuelas aumentan los contagios de los padres y maestros, pero se pueden reducir mucho con medidas correctas de protección:

science.sciencemag.org/content/early/…
3/ Lo cual es consistente con otras líneas de evidencia.

Como explicamos en este preprint, una escuela con la ventilación mínima de ASHRAE (o menos, que es lo típico) tiene bastante riesgo. Pero con mascarillas, ventilación, menos densidad, se mejora muchísimo. (Linea verde)
Read 5 tweets
Jose-Luis Jimenez Profile picture
4 May
1/ UPDATES TO COVID-19 AEROSOL TRANSMISSION ESTIMATOR

We have just implemented several updates:
- added increased risk of variants
- made clearer how to enter vaccinated people
- added calculation of infection risk parameters

tinyurl.com/covid-estimator
2/ The risk parameters allow quantitative decisions on which mitigations are needed to avoid outbreaks. See the thread from yesterday on that topic and paper:

3/ We also added a sheet with a quantitative version of the BMJ table (bmj.com/content/370/bm…). See sheet "Risk Table", where you can modify it for your conditions.
Read 8 tweets
Jose-Luis Jimenez Profile picture
2 May
1/ A SIMPLE WAY TO ESTIMATE THE RISK OF INDOOR SUPERSPREADING

Our preprint using the airborne transmission model

Captures the literature outbreaks well. So we can use it to see whether an activity is at risk of superspreading

Also to compare diseases

medrxiv.org/content/10.110…
2/ It can be very confusing to estimate how risky different activities are, depending of size of space, duration, number of people, vocalization, intensity of breathing, ventilation, air cleaning, masks + their quality + fit.

We combine it all into a single parameter, rigorously
3/ We'll explain the parameter(s) later, but first let me convince you that it works.

The key is Fig. 1 b:

- X-axis is risk parameter in log. scale. MUCH riskier to right, MUCH less risky to left
- Y-axis is attack rate (% of people present infected in outbreaks)
Read 34 tweets
Jose-Luis Jimenez Profile picture
30 Apr
1/ Dental office visit

Small room, windows closed, no ventilation system. CO2 got to 1350 ppm. Probably ~3 ACH, given rise time

Both me and provider vaccinated. Provider wearing well-fit KN-95 and eye protection. I wore surgical mask over nose, breathed from there + eye prot.
2/ They had small air purifiers by Medify (relative size as in pic; medifyair.com/products/medif…).

Reception area: set at 1 of 3, could not feel any air. Turned to 3, made more noise, started to feel air.

Procedure room: set to 2, I asked to turn to 3, noisier
3/ Not impressed, despite some precautions. I was not too concerned due to vaccination. But there ar other respiratory diseases, they need to do better, I'll let them know.

Repeated problem: HEPA filters viewed as "talisman" by being there. Even if too small and at low setting!
Read 4 tweets

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