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.
A quick hit on the dose-response.
"Dose-response
Since the beginning of the pandemic, several animal studies looked at the dose-response relationships for symptoms, seroconversion and viral shedding through orotracheal [140], intranasal [141] and aerosol [142] exposure. Most recently, a human challenge study enabled the identification of the Median Tissue Culture Infectious Dose (TCID50) or the inoculum dose that induced infection in more than 50% of participants, corresponding to 10 TCID50 or 55 Focus-forming Unit (FFU) [143]."
What the heck is a focus-forming unit you say?
"A measurement of the concentration of live virus in a given amount of fluid. This is measured by spreading a known amount of the fluid over a layer of cultured cells which are infected by the virus, then counting the number of areas in the culture which look infected."
