Big thank you to @EricCarroll for pointing out this new WHO document on SARS-CoV-2 transmission.
This document is pretty complex, in-depth, dense, and I still expect it to evolve as we learn along the way. They have some of the correct people to be working on this, for once. Hello Lidia Morawska signing off on it at the beginning of the forward.
First, a tldr. If you don't care about how it came to be, or the science, and just want to know the outcome, here it is:
https://partnersplatform.who.int/tools/aria
Go to the calculator, enter your data, and come out with a probability of infection in a given situation along with the number of expected secondary infections from that interaction.
Here's the document itself if you want to follow along:
https://iris.who.int/bitstream/handle/10665/376346/9789240090576-eng.pdf?sequence=1&isAllowed=y
Disclaimer - This is evolving science.
I'm going to split this up in a thread, because I took a lot of notes of what stood out to me on a first read, and I hope to come back to it, and use it as a general reference moving forward.
"The first component is the emission rate defined as the number of virus-laden particles exhaled by an infected person per unit of time."
"The second component affecting the inhalation transmission mechanism is the removal rate which can be defined as the total number of aerosolized virions removed from the air in a given time."
"The difference between the emission rate and the removal rate leads to the third component, the exposure. This component can be defined as the concentration of virions in ambient air, during a given time, at which a susceptible host comes in contact with."
"The fourth component is the cumulative or absorbed dose--meaning the total number of infectious particles inhaled and subsequently absorbed by a susceptible host during the exposure event."
"Finally, the pathogen infectious dose, the host immunological status and the specific SARS-CoV-2 variant transmissibility, contribute to the complex dose-response model which, in combination with the cumulative absorbed dose, define the host probability of infection which completes the fifth and final component."
I'll add their infographics of each of these components in the next post.
