Thread by @JenniferKShea

It's widely accepted that #MeaslesIsAirborne

I summarized the evidence for airborne spread of Measles vs. COVID-19 in a table

The results were quite shocking to me ...

How is it that we are still discussing whether or not #COVIDisAirborne??

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The disease on the left is managed with airborne precautions, including respiratory protection (N95/respirator) and ventilation optimization

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In Canada, the disease on the right is still managed with droplet and contact precautions (gowns, gaping surgical masks with substandard filtration efficiencies, gloves, face shields and plenty of hygiene theatre)

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"But - you forgot the row that shows measles is way more contagious than COVID-19!"

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The only thing holding some back from saying that #COVIDisAirborne:

Historical R0 for Measles (cases easily identified via rash) > estimated R0 for a novel virus with many asymptomatic cases, that is spreading despite worldwide masks/distancing/lockdowns

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It's important to reiterate that when experts are yelling "it's airborne!" - they are not imagining green wafts of toxic gas leaking through the air ducts to infect 80-100% of people in a hospital or office building...

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A well-designed and functional HVAC system should help to PREVENT airborne spread, not promote it.

Airborne spread of ANY airborne disease will occur most commonly at close-range to an infected person, through inhalation of their concentrated aerosol plume

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Spread can also occur through #SharedAir in poorly ventilated indoor spaces via build-up of infectious particles that linger, like smoke

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Aerosol exposure will not be equal throughout a space/office. The Bloch Measles study illustrated this nicely in 1985. They released 1-30um sized aerosols containing NaCl from the office containing the source patient. Note the varying concentrations...

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* Riley 1978 school outbreak study is commonly quoted as proof that Measles transmits THROUGH HVAC systems. There are several weakness with this study:

1- They assumed that is was spreading via HVAC and that there was NO significant spread in the cafeteria or gym...

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2- They did NOT attempt to isolate RNA or viable virus from the HVAC system, nor did they complete airflow studies to see how an aerosolized virus would mix within the rooms/hallways/etc

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3 - They gloss over the fact that the original explosive outbreak involved kids from 2 wings of the school (which had completely independent HVAC systems!). Kids from the new wing ate lunch in the old wing cafeteria...

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I welcome any feedback re: critical studies that may be missing from this table

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Azimi et al 2021 - pnas.org/content/118/8/…
Bischoff et al 2020 - academic.oup.com/jid/article/21…
Bloch et al 1985 - pubmed.ncbi.nlm.nih.gov/3982900/
Chia et al 2020 - nature.com/articles/s4146…
De Jong et al 1964 - nature.com/articles/20110…
Eichler et al 2021 - wwwnc.cdc.gov/eid/article/27…

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Goldberg et al 2021 - academic.oup.com/ofid/article/8…
Günther et al 2020 - embopress.org/doi/full/10.15…
Klompas et al 2021 - acpjournals.org/doi/full/10.73…
Klompas et al 2021 - academic.oup.com/cid/advance-ar…
Kutter et al 2021 - nature.com/articles/s4146…
Lednicky et al 2020 - ijidonline.com/article/S1201-…

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Miller et al 2020 - onlinelibrary.wiley.com/doi/10.1111/in…
Nissen et al 2020 - nature.com/articles/s4159…
Remington et al 1985 - pubmed.ncbi.nlm.nih.gov/3974036/
Richard et al 2020 - nature.com/articles/s4146…
Riley et al 1978 - pubmed.ncbi.nlm.nih.gov/665658/
Santarpia et al 2020 - nature.com/articles/s4159…

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van Doremalen et al 2020 - nejm.org/doi/full/10.10…

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Thanks @jmcrookston for this interesting article from September 2020 challenging the idea that R0 for Covid is only 2-3

royalsocietypublishing.org/doi/10.1098/rs…