Thread by @DRTomlinsonEP

'Proof' that 100%* of SARS-CoV-2 transmission is via the airborne [aerosol inhalation] route

@mjb302 I blame you!
@microlabdoc @hughes_eilir @Linzofm87 @huwwaters

[*to the nearest integer: obvs only ~1:10,000 fomite / contact from @CDCgov]

Pic h/t @Don_Milton

/n

1. 85% of viral RNA is in <5 micron diameter particles, which are released during normal physiological processes.

👉 Base airborne vs large droplet transmission route probability

5.6 : 1

Kudos @drkristenkc @Don_Milton & team.

https://twitter.com/DRTomlinsonEP/status/1417233866297860099?s=20

2. SA of nasal mucosa with ACE2 & TMPRSS2 receptors vs total lung parenchyma.

Sinuses? I'll be generous

Say, 20 x 20cm = 0.04m*2

Lung parenchyma: ~91 v 118 m*2, F v M (mean 100)

👉 Airborne vs large droplet probability now

5.6 x 2,500 = 14,000 : 1

pubmed.ncbi.nlm.nih.gov/1626135/

3. Biological defence mechanisms:

Sinuses: mucociliary barrier & clearance, enzymes etc

Alveoli: no significant mucous barrier

Summative effect - factor of 400 (ref).

👉 Airborne vs large droplet transmission probability

14,000 x 400 = 5,600,000 : 1

https://twitter.com/DRTomlinsonEP/status/1387824725439795202?s=20

4. Physics & behaviour

Large droplets: require donor & recipient alignment of face, height, particle velocity, no blinking etc

Aerosol: when did your lungs last blink?

As we're already at >5 million : 1 probability in favour of airborne I'll give you this for free

5. Behaviour (cont'd)

Large droplets: drop to the floor; intermittent release & only during speech / coughing / sneezing to any significant degree

Aerosols: constantly released by donor & inhaled by recipient according to proximity concentration gradient

...

5. (cont'd)

Summative effect - guesswork!

Being incredibly generous to large droplets, this reduces probability of their transmission compared to inhalation, 10-fold.

👉 Airborne vs large droplet transmission probability

5,600,000 x 10 = 56 million to 1

Convinced? 😇

End